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Author Topic:   2004 170 Montauk 4 stroke carburetor problems
WT posted 07-06-2006 09:36 PM ET (US)   Profile for WT   Send Email to WT  
I have a 2004 170 Montauk with Mercury 90 hp 4 stroke.

During my first 100 hour service, the dealer cleaned/rebuilt my carburetors and charged the work back to Mercury as a warranty item.

I dropped off my Montauk for its 200 hour service Monday. I was informed today that they cleaned/rebuilt my carburetors once again. They told me the carburetor work was "no charge" and that they will send the repair bill and notes back to Mercury as a warranty item.

I asked if the carburetor problem is wide spread. The response was that Mercury is aware of 90 hp 4 stroke carburetor "problems".

Are there any 170 Montauk owners that have had their Boston Whaler dealer permanently fix the current carburetor problem?

Thanks for any input. I will pick up my Montauk either tomorrow or Saturday. I want to know if I should ask for a permanent fix. I also would like to quote fixes that other dealers have performed. (Perhaps Mercury will give me a great deal for an EFI setup?)



sosmerc posted 07-07-2006 11:36 AM ET (US)     Profile for sosmerc  Send Email to sosmerc     
All 4 stroke carbs have VERY small jets and passages. It is important to have a good fuel filter system and to have fresh clean fuel. I would recommend using StarTron fuel additive AT ALL TIMES in your fuel. This and a good filter system such as a RACOR should prevent most carb problems.
If you have a 4 stroke with multiple carbs, do not attempt to adjust the linkage unless you have a factory manual and really know what you are doing. These 4 stroke carbs are VERY touchy and proper synch and link is critical for best possible running quality.
bobeson posted 07-08-2006 01:45 AM ET (US)     Profile for bobeson  Send Email to bobeson     

Trying to cast the 90hp mercaha carb problems as being generic four-stroke carb issues does not ring true. These are not your average multi-carb four-stroke engine problems. I've been an involved with multi-carb four-stroke motorcycle engines for years, including plenty of rebuilds and tuning efforts, and this engine has much worse problems than any of those engines commonly exhibited. Given the widespread nature of the issues people are experiencing with this engine, I think it's safe to conclude that a design problem exists. Maybe it is something else manifesting in the carbs, such as fuel lines decomposing from ethanol or some such thing, but whatever the cause, there is certainly an overabundance of problems with this engine's fuel delivery system.
bigjohn1 posted 07-08-2006 07:54 AM ET (US)     Profile for bigjohn1  Send Email to bigjohn1     
How are we calling this "widespread"? Its true this has come up a few times in the recent past but some of those cases where situations where folks left un-stabilized fuel in their carbs all winter long. It is my personally held belief that Merc under-jetted those carbs so the engine would pass the 3-star compliance thing. I may be wrong but that is my hunch. One thing I am convinced on regarding this engine in the 5 years (I think) it was produced - useage level of the engine and the use of an appropriate fuel additive makes all the difference. I say that as many, many of those 90 4-stroke Mercaha's (sold in the overseas Mariner trim) are all over Guam and people don't seem to be having any problems with them.

Warren - did the dealer say why he re-built the carbs on either visit? Was the engine running rough and/or did you request they be rebuilt?

I don't have a dog in this fight and have no ties to Mercury. I make my observations based on what I see for myself. I know quite a few local boaters here with that engine and nobody has had a carb problem.

WT posted 07-08-2006 11:48 AM ET (US)     Profile for WT  Send Email to WT     

At times my Montauk would die at idle or low rpms. Sometimes, in order to start my boat I have to get it out of neutral to give it more fuel to get it started.

I did not know that I need a rebuild at the 1st 100 hour or my 200 hour service. I just thought that my motor needed adjustments (throttle linkage, idle, etc.)

I was told to use Quickleen at my 100 hour service and have been doing so. I was surprised that the carburetors were gummed up again. Perhaps it's happening more to me because I leave my Montauk outside in the sun? The California heat dries out the carbs and plugs up the tiny jets?


MosslandingJoe posted 07-08-2006 07:12 PM ET (US)     Profile for MosslandingJoe  Send Email to MosslandingJoe     

I don't want to curse my 04 170 but I have had few problems with the carbs, and then only when it sat with untreated gas for an extended period.I currently use gum-out and sta-bil in every tank, this combined with chevron mid grade gas seems to be keeping things running well. But I do keep her in the garage.
I am interested in who is your dealer? Mine is "The Outboard Motor shop" Jay over there told me that they had been having problems with the carbs and early models but thought they had cured the problems with the addition of a fuel filter. Not being too interested in home service of my 170 I can not give you the details as to which particular fuel filter they added. I take my 170 to a certified Merc dealer in Morgan Hill, CA. At the 100 hour service the carbs were adjusted but not rebuilt, my 200 hour service will be this summer so we will see about that service and the carbs, but so far she is running well,with several outtings into the bay this season.
I have talked with other 170 owners with same motor and they also have had no problems as long as every tank contained "treated" gas, every tank....If I have any unused gas and know it will be more than a week or two before usage that gas either goes in my car or weed whacker, pressure sprayer etc...and my engine is run to empty. On any subsequent startings if there is any trouble(I do this before venturing out) I do not hestate to spray Gum-Out into the manifold. Now I can not argue the relative merits of fuel additives,so I do not know if Gum-Out is any better/worse than Quikleen or if I should not be using Gum-out.The label seems to indicate that usage for my 170 is ok, and it's just what I have always had around for use on my Harley(also carbs).
I know that some members think that usage of "treated gas" and attention to this kind of a detail indicates some sort of design problem in an engine of this expence,and it may be that is the case. But to me that is just the price of having this kind of fun. What I am trying to say is that if we look at other recreational forms of self indulgance then treated gas is a small price to pay, after all we don't have to rebuild our motors as often as the piper cub owners, and how many "Hog" owners with 30k machines are always changing "Stuff" way expensive stuff.If for example Harley's came with this kind of carburation "Problem" many people I know would not hesitate to swap out every carb from the factory with Mikuni's even if they had to custom make adapters for them and not blink or look back,it would just be please don't complain too loudly, this is after all a way cool boat. WT please don't consider this as an attack of any kind on you, it's just that recently I have read many complaints regarding the 170....

WT posted 07-09-2006 12:41 AM ET (US)     Profile for WT  Send Email to WT     

I own 4 watercraft. A 14 foot aluminum Western with 25 hp Mercury 2 stroke, a 2 stroke SeaDoo, partners in a 1975 19 foot Boston Whaler Revenge and my 170 Montauk. My Montauk is my favorite.

I have never had problems with carbs on my other watercraft (yet).

1) My Montauk was purchased at Outboard Motor Shop and came with a fuel filter with the purchase of a 24 gallon Pate gas tank.

2) I use Quickleen and mid-grade Shell gasoline. I may be throwing money away but I only use mid-grade or premium gasoline in my gasoline vehicles. I do this under the perception that the higher grade fuel has more cleaning additives in it.

Should Boston Whaler/Mercury Marine place a warning label on the gas cap stating that Quickleen is mandatory in order to keep carburetor jets from getting gummed up?


swist posted 07-09-2006 07:40 AM ET (US)     Profile for swist  Send Email to swist     
I haven't had any trouble with mine, but maybe that's because after reading all these threads I decided to run Stabil year round. Is this the same as running Quickleen? Would you use both?
divefan posted 07-09-2006 11:37 AM ET (US)     Profile for divefan  Send Email to divefan     
Funny this topic should come up again this soon. Here is the link to a thread I started titled:

'90 HP 4-Stroke 2004 model 100 hour service'

It started as a question about the 100 hour service but has a lot in about the very issue you raise in your thread.

The carb problems with this engine is a well documented issue that Mercury has known about since the motor came out. They have chosen to do the standard corporate thing which is to blame the consumer for the problem and do nothing at the dealer level to help out the consumer. Anyone who has a dealer good enough to write the carb service up as warranty work is lucky. Otherwise you have to pay for it like I and others did on a brand new engine. And will continue to have to pay for in the future. There are some real horror stories out there of what some people have gone through owning this engine. Forget about Mercury. They have moved on and are now in the 'Verado' era. This is just a sad chapter for them that they are trying to forget about. You will get no satisfaction by speaking to them. I tried and did. Zero.........

whale tauk posted 07-09-2006 12:13 PM ET (US)     Profile for whale tauk  Send Email to whale tauk     
Hi WT,
My 2004 had starting and idling problems which occured within the first 30 hours. During that time the engine sat for periods of up to a month without draining the carbs. A Mercury mechanic told me to run Stabil and run the motor hard when I was out as well as drain the carb bowls if it was to sit longer than two weeks. It has been okay since. I changed the oil at 30 hours and at fifty hours noticed that the level had increased. I then sent a sample of the oil to Blackstone labs. The report indicated fuel dilution of 2.3 percent. The report went on to say that they often encounter marine engines with fuel dilution like mine as trolling and idling can be a major contibutor. They also said that the rings may still be seating.
I rented a public dock slip for a week recently, ran it hard every day and it seemed fine.

whale tauk

high sierra posted 07-09-2006 10:47 PM ET (US)     Profile for high sierra  Send Email to high sierra     
I always use Sta-bil and run the hell out of my 115 fuel injected mercury. Never a problem. High sierra
bigjohn1 posted 07-10-2006 07:51 AM ET (US)     Profile for bigjohn1  Send Email to bigjohn1     

Honestly, I can't see where leaving your boat out in the sun would be a root cause for gumming up the carbs - unless it is sitting around so long between outings that the fuel is going bad. It sounds to me like you use your boat often enough where that is not the case.

I am truly sorry to hear of your problems as well as divefan's and others on this particular engine. This makes me glad I sprung the extra dough for the 115efi and was able to avoid the carbs altogether. Even though I have the efi system, I still de-carb every 100 hours (like the 90 and 115 manuals both state). I personally use Deep Creep for this and I also run the Quikclean in all my fuel. Since I boat year-round and gas never gets old, I don't need Stabil thankfully.

After you get this all sorted out, I would recommend the 100 hour de-carb and regular use of Quickleen. Some folks think a de-carb of 4-strokes is a waste but since the factory states to do it, I reason that I can't go wrong.

I am personally very skeptical of service departments, whether it be boat, auto, or other. My Whaler dealer actually told me to never de-carb my 4-stroke with the Mercury-recommended Power Tune as it would cause the engine to starve for oil and possibly seize. They also told me my timing was non-adjustable. I went home and read the factory manual for my engine and found both of those statements to false. The way I now approach maintenance on my outboard is to first identify what the book says to do at what interval. I then take it to the dealer for the items I either can't do or don't want to do. I am very clear in instructing them on EXACTLY what they are to perform on my engine.

Good luck in resolving this....

David Livingstone posted 07-10-2006 11:58 AM ET (US)     Profile for David Livingstone  Send Email to David Livingstone     
Warren, it could be apples and oranges, but I was told to use the cheapest possible fuel that I could find for my 1998 Yamaha F100 Four Stroke. Both Tuppens Marine in Lake Worth, Fl, USA and my own dealer back home in the great white north. They both said high test would cause air problems in the fuel.


Barney posted 07-10-2006 12:31 PM ET (US)     Profile for Barney  Send Email to Barney     
David, Your Yamaha has the same powerhead as the Mercury. Maybe the same carbs. Any idea what carburators you have? Even with the same powerhead the factory manuals seem to be quite different. Jim
mikeyairtime posted 07-10-2006 04:16 PM ET (US)     Profile for mikeyairtime    
I put a fuel shut off on mine and run the fuel out of the carbs everytime I run it. Durring the off season I use StaBil but not durring the fishing season. No problems since I put in the shut off. I use the cheapest regular I can find usually Arco or Costco.
fishinchips posted 07-10-2006 08:13 PM ET (US)     Profile for fishinchips  Send Email to fishinchips     
maybe mercury should give us a lifetime supply of quickleen or have all the exiting 170's get fuel shut off valves ???


17 bodega posted 07-15-2006 12:27 AM ET (US)     Profile for 17 bodega  Send Email to 17 bodega     
In my Yamaha T50 4 clyinder carburated engine (with 1000 hours of hard use), I leave the boat outside in the baking sun, don't use any fuel additives, use the cheapest gas, leave gas in the tank all winter, and haven't had one problem.

I am the worst possible boat owner when it comes to meticulous treatment of fuel and engine. I do check the oil though.

The boat has run like a champ. She's in for her 900 hour service at about 980 hours.


divefan posted 07-16-2006 05:32 PM ET (US)     Profile for divefan  Send Email to divefan     

That's been my point all along. No small outboard marine engine should need such constant and meticulous short term maintenance in order to run well. Or, as in some cases to run at all! This is not a hi-tech hi-performance racing power plant that is sold to a highly sophisticated buyer that expects to overhaul his engine every time it's run. It's an engine that matches (or should match) the boat package it's hooked up to. An everyday, low maintenance, fun package, for the average 'Joe' and his family.

What about the hundreds of owners that do not read these posts and have no idea what is going on and have to rely on the B.S. they are getting from Mercury and Whaler about their problems?

There is obviously something wrong in the way the carb system was designed. No one is taking responsiblity.

17 bodega posted 07-20-2006 12:14 AM ET (US)     Profile for 17 bodega  Send Email to 17 bodega     
Your point is well taken Divefan,

It is impossible to ignore the fantastic performance and reliability of the Japanese made engines, both in automobiles and outboard motors.

Look at the labor issues associated with US manufacturing... is the outcome such a surprise? We're treading into no brainer territory on this one. I want to support American workers and their families, but I don't want an inferior product with my hard earned money.

whaler1234 posted 09-03-2006 06:02 AM ET (US)     Profile for whaler1234  Send Email to whaler1234     
I just experienced my first problem with my 2004 170 Montauk with Mercury 90 hp 4 stroke. I have not run the motor for two months, but today it did not want to start. After 10 minutes of sputtering, the motor finally kicked over. After what looked to be normal idling, I took it out for a high speed run. A few minutes later, it started vibrating and dropping rpms. I turned around and called it quits. The motor has 40 hrs and is treated with Stabil religiously. I'm hoping its not related to gumming of the carbs, but it looks to be another case. We'll have to see after a trip to the dealer.
Barney posted 09-03-2006 07:22 AM ET (US)     Profile for Barney  Send Email to Barney     
whaler1234, Mine has done that after just three weeks of sitting. It will eventually clear, maybe 20 minutes or so. I've taken mikeyairtime's advice and installed a shutoff valve. Will try it out tomorrow. Jim
WT posted 09-03-2006 09:34 AM ET (US)     Profile for WT  Send Email to WT     
Do you guys have a Pate gas tank? Perhaps it's the ethanol in the gasoline that is causing the Pate tank to deteriorate thus gumming up the carbs.

Let us know what the dealer says.


bobeson posted 09-05-2006 03:26 PM ET (US)     Profile for bobeson  Send Email to bobeson     

This sounds a lot like the problems I've had repeatedly with my 2003 Montauk 170 / Merc 90hp four-stroke. My regular routine when using the boat after more than a few weeks of inactivity is to replace the fuel in my pate tank with fresh fuel, add carb cleaner to the new fuel, and try to start it up. When it still gives me trouble starting, I spray a little Thrust (or whatever brand of starting fluid it is I have now) into the air intake, and that gets it running. Then I rev it up for a while to clean out the gunk as much as possible, and it usually settles in to a decent condition before too long. After about 30 minutes of >3K RPM running, the motor is usually pretty happy again.

I also synchronize my carbs every few months, and that really helps a lot with how smoothly the engine runs when it decides to cooperate, but it doesn't prevent the carbs from fouling up again of course. I bought an electronic vacuum gage that makes synchronizing the carbs pretty quick and easy. I don't know why they get out of synch as quickly as they do, it might be related to the residues changing performance as they build and and get cleaned away, but every time I go to recheck the syncronization they are a little out of where I left them last time.

For what it's worth, I do have a Pate 24-gallon tank that I had the dealer install when I bought the boat in the fall of 2002. I have no idea if this is contributing to the problem or not.

whaler1234 posted 09-05-2006 05:38 PM ET (US)     Profile for whaler1234  Send Email to whaler1234     
I just came across an informative website discussing ethanol in outboards.

Of particular interest is this article listed at the bottom of the page: "Is Winter Fuel Gumming Up Your Outboard?"

whaler1234 posted 09-06-2006 05:03 PM ET (US)     Profile for whaler1234  Send Email to whaler1234     
The cause of my problems appears to be particles in the fuel system. My shop states they found particles of sandlike material in my 6gal. tank which most likely ended up in the carbs. <Would the stock filter block these particles?>

End result, they will be rebuilding the carbs.

They recommend cleaning the fuel filter religiously (every mo.) and also dumping the fuel and replacing w/ chevron or shell.

Merc is covering some of the cost as a cust service, but it's still painful to shell out this much money for a motor w/ only 40 hours and which is maintained by the book.

Going forward, I'll most likely use quickleen in addition to the stabil that I'm using now... and drain/clean the stock filter monthly.

Buckda posted 09-06-2006 05:18 PM ET (US)     Profile for Buckda  Send Email to Buckda     
That seems like a lot of work for a "reliable" engine.

What I mean is, replacement / draining of a fuel filter every month is much more maintenance than what I would consider "routine".

Every 100 Hours...okay, but every month?

That sounds like a problem with contaminated fuel more than anything else - but your filter should be able to handle more than a month of use unless your fuel supplier is really bad.

Thankfully for those buying new Merc engines, they are now EFI rather than carburated, which I assume has gotten rid of these problems - and the OptiMax (DFI) never has had these problem reports.

Divefan is right:

No small outboard marine engine should need such constant and meticulous short term maintenance in order to run well. Or, as in some cases to run at all! This is not a hi-tech hi-performance racing power plant that is sold to a highly sophisticated buyer that expects to overhaul his engine every time it's run. It's an engine that matches (or should match) the boat package it's hooked up to. An everyday, low maintenance, fun package, for the average 'Joe' and his family.

I'm suprised by all the reports of problems with no factory fix yet...but I suppose after spending hundreds of millions of dollars on R&D for VERADO, the CFO is tired of writing checks!

bigjohn1 posted 09-06-2006 08:07 PM ET (US)     Profile for bigjohn1  Send Email to bigjohn1     
Whaler1234, an owner of your engine with the same problems reported a few months back that their silver-colored quicksilver fuel line was the cause of the particles in their carbs. Apparently, some type of internal coating came off. You might want to do a search and follow up on this idea as a potential cause or contributing factor. Just an idea....
Barney posted 09-06-2006 08:16 PM ET (US)     Profile for Barney  Send Email to Barney     
With regards to the stock filter and the clear plastic filter housing:

I don't think the housing will hold up to monthly removal and reinstallation. It is plastic but requires large pliers to remove and to tighten. It is also soft and damaged easily.

I recommend installing an extra remote filter like a Racor and be done with the filter problem.

Even with eliminating water and proper filtration, the carbs will still "act up" from fuel left in them for a couple of weeks.

Side note: Pre-Katrina mine was run often, twice a week. It never gave me a problem when lots of fuel was flowing thru it. The local marine law enforcement had one of these outboards with over 1500 hours on it with no problems. Poor fuel filtration and sitting idle is the death of this outboard.


WT posted 09-06-2006 08:28 PM ET (US)     Profile for WT  Send Email to WT     
My Boston Whaler dealer changed my fuel line during the 200 hour service of my 2004 170 Montauk.

Perhaps this will fix the gumming of the carbs?


Maximus posted 09-06-2006 10:16 PM ET (US)     Profile for Maximus  Send Email to Maximus     
I also synchronize my carbs every few months, and that really helps a lot with how smoothly the engine runs when it decides to cooperate, but it doesn't prevent the carbs from fouling up again of course. I bought an electronic vacuum gage that makes synchronizing the carbs pretty quick and easy. I don't know why they get out of synch as quickly as they do, it might be related to the residues changing performance as they build and and get cleaned away, but every time I go to recheck the syncronization they are a little out of where I left them last time.

Can you provide a detailed right up on how to synchronized the carbs on this motor? Also, can someone provide a detailed procedure on running the carbs dry in preparation for winterization?

I may be in the minority, but I just turned 200 hours and have not had any fuel related problems. I run Techron with each tank (or there abouts) and use the boat every weekend. The longest stretch betwen uses has been about a month, other than winterization.

The ethanol scare drove me to install an external Mercury fuel/water separator filter.

JoeyP posted 09-07-2006 01:14 PM ET (US)     Profile for JoeyP  Send Email to JoeyP     
The truth is that we just don't have an accurate sample of the 90 HP 4strk carbed owners. Only a few actually report on this site. Some saying no problems so far and others with possible fuel/carb issues.

I just picked up a 2005 Montauk with this motor. I already told the dealer that I will be his biggest pain in the "A" if this motor fails to perform.

bobeson posted 09-07-2006 04:18 PM ET (US)     Profile for bobeson  Send Email to bobeson     

A detailed write-up on carb synchronization? Well, I might get around to writing something Extra Special and detailed the next time I go though a carb rebuild, 'cause I've been meaning to take pictures of that process, but for now I'll just jot down a quick summary:

1) Hook up each channel (4 of them) of your fancy-pants Vacuum-Mate digital vacuum gauge synchronizing tool to the ports on the intake manifold designed for just this purpose. (You can also use mercury-tube carb synchronizing tools that are much cheaper and easier to find but more annoying and a little riskier because of the liquid mercury.) You just remove the plug bolts and screw on the fittings at the end of rubber hoses that connect to the synchronizer. This allows each cylinder's intake pressure to be measured independently and compared.

2) Fire up the motor, run it at 1K RPM. You need to have the motor in a test tank for this, not just hooked up to earmuffs, because the exhaust backpressure affects the input pressure as well. In fact, to do a really good job of this you're supposed to have the boat in the water tied up firmly to a dock so you can rev it up while in gear, but that's too much hassle for my usual procedure. For setting the mixture screws this is supposed to more critical, but I haven't really gotten the hang of doing that procedure properly yet. There's a bit of art to that process. I just do the best I can manage while in a test tank with the transmission in neutral. I use a large rubbermade plastic tub, and I'm pretty satisfied with the results overall.

3) Now watch cylinder #1 (lowest) as the benchmark reference. Adjust the throttle linkage position adjustment screw (I'm forgetting the proper name for this screw right now) for each carb in turn until the vacuum on each cylinder reads roughly the same as the #1 cylinder.

4) Rev up the engine to about 3K-4K RPMs and watch how the individual cylinders react - they should all track each other roughly the same. There will be some small variation in the dynamic response of each cylinder to the trottle changes - you want to minimize the differences, but in practice it's almost impossible to get them to be entirely identical.

5) After a few throttle increase cycles, put it back to 1K RPMs and re-adjust so they are all pulling the same vacuum again. Repeat this cycle a few times until they are all synchronized and stay synchronized following the throttle increase. Usually I also synch them while the motor is running at 3K RPMs, which the Merc shop manual does not specify, but that's how my motorcycle mechanic buddies used to do things, so I still do that step too. It's an iterative process to keep adjusting everything until they are all well syncronized.

6) Shut down the engine, pull the synchronizer hoses off and put the plug bolts back on the intake manifold, put the cowling back on, hope your neighbors aren't too peeved about all the noise, and go boating.

Your mixture screws might need to be tweaked along the way too. There are little plugs covering the mixture screws that need to be pulled out before you can adjust them (these plugs are a CARB compliance requirement, IIRC, but not being able to tweak your mixture sucks). As I mentioned, though, the mixture adjustment process is still something I'm figuring out, so I'll leave that explanation for someone else to document properly. The process I've always had explained to me is to adjust each mixture screw in and then out until the RPMs reduce by some threshold (the exact number usually varies, I often hear 500 RPM) and then leave it in the middle of that adjustment range. In practice, it never seems to go as simply as that, so I try to follow that procedure and then keep screwing around (haha) until the motor seems to be running as smoothly as I can get it. I've never seen anybody do a proper job of this using an exhaust gas analyzer with motorcycles, my mechanic friends always just did some variation of iteratively trying different settings until it all seemed to run well. There are also ways gauge your mixture and jet settings by checking the condition of your spark plugs that involve quickly shutting down the motor after running at full power, which is supposed to visually indicate the fuel/air mixture results. After watching a friend do this by the side of a busy freeway, I've never had the desire to do it myself. I don't know what process the professional outboard mechanics follow for the mixture adjustment.

bigjohn1 posted 09-07-2006 05:11 PM ET (US)     Profile for bigjohn1  Send Email to bigjohn1     
Barney - if your filter requires pliers to remove, someone installed it too tightly, either at the factory or during the last service. It should NOT require pliers for either removal of re-install. Re-install hand tight so you dont smash the o-ring or damage the plastic threads.
Barney posted 09-07-2006 06:15 PM ET (US)     Profile for Barney  Send Email to Barney     
Yep, factory put it on so tight pliers were required. Kinda like removing an oil filter the first time on a new car. Hand tight results in a leak though. New o-ring might solve this after every removal. When I got it to stop leaking I left it alone. To me it is very fragile, and monthly service would kill it. Doesn't matter now, I have the bigger filter. Jim
Maximus posted 09-07-2006 08:22 PM ET (US)     Profile for Maximus  Send Email to Maximus     
bobeson, thank you.

The synchronization process simply matches individual intake vacuums by adjusting the throttle actuation arm length, but does not optimize intake vacuum to a level....correct? To optimize individual intake vacuum you need to mess with each mixture screw?

bobeson posted 09-08-2006 06:04 PM ET (US)     Profile for bobeson  Send Email to bobeson     

Maximus, I'm not sure I entirely understand your question, but I'll try to answer anyhow.

The individual intake vacuum levels are controlled by the throttle screw adjustments at each carb, so you can get them to be the same at a given RPM without touching your mixture screws. I find that the dynamic response to throttle control changes varies from cylinder to cylinder unless you have your mixture screws optimized for each cylinder.

So, in a sense, the throttle screw adjusts your static vacuum levels while the mixture screws adjusts your dynamic vacuum levels. That's a simlified view, but seems to hold water for the purposes of performing a backyard carb synchronization.

Anytime you adjust either screw both static levels and dynamic responses will be changed, which is why this becomes an iterative process to optimize all the variables. You set the vacuums to be equal at a static throttle position, then rev it up and watch the dynamic response of all the cylinders, then adjust the mixture screws a little until they respond more equally to throttle changes, then the static levels will be unequal again so you adjust the throttle screws until the levels are the same again, then check dynamic response, etc. And for good measure I sometimes also perform the mixture adjustment method I previously mentioned where you dial the mixture screw in and out until the RPMs change a little, then set it to the middle of the range. This method messes with the mixture more than I suspect is optimum, but as long as I don't go overboard on the mixture adjustments it seems to result in very nice performance of the motor. All told I usually take about 20-30 minutes to perform this procedure, from cowl off to cowl back on.

After running the motor for a while it's a good idea to pull the plugs and do a visual inspection to make sure they're all burning with roughly the same mixture. I'll do this after I return from the first trip out following a carb synchronization. So far I haven't found any issues.

If anybody has a better method of optimizing the mixture settings I'd love to hear it.

whaler1234 posted 09-12-2006 05:16 PM ET (US)     Profile for whaler1234  Send Email to whaler1234     
Well, I took the 170 out for a spin... it started out running poorly, but after some time the motor finally started to sound normal. It now runs okay.

Only problem now is that my top speed has dropped from 40 to 31mph and the powerband has decreased throughout.

The manual states performance loss could be attributed to:
- low oil pressure
- throttle not fully open
- damaged or improper size propellor
- incorrect engine timing, adjustments, or setup
- boat overloaded
- excessive water
- boat bottom is dirty

Since the carbs were just rebuilt and I was able to hit 40 on my last outing, my guess is the throttle or incorrect timing, adjustments, etc.

RioRaft posted 09-18-2006 01:56 PM ET (US)     Profile for RioRaft    
Well here is my two cents, and I am not a happy camper either. 2003 170 Mercury 90 4 stroke (three years extension to the warranty), 27 Gallon Pate tank. Here is the environment it lives in: Goes into the water Sea isle City, NJ in April gets used at least twice a week every week and comes out late December. The boat ran great for the '03, '04, '05 seasons, this year, first year for ethanol in NJ waters, it runs very rough or stalls out at low RPMs and runs like a champ at RPMs above 3000. I contacted my local BW dealer and although he was very nice (they have been great to deal with) he gave me the basic skinny on the problem as he sees it and has dealt with it on several Merc 90HP 4 stroke engines.
Here is a bullet version of what I was told:
He is having this problem with just about every 90 Hp 4s they have sold.
Mercury is classifying this as a fuel contaimination problem. Merc has moved on to the EFI version and not responding to problems with these engines.
This engine was designed for very low fuel consumption and thus the idle jets have an extremely small openings.
The ethanol in the fuel grabs water from where ever it can get it and causes a gel type consistency that gets clogged and hardens in the idle jets and the carborator.
The answer according to them:
Bring in the Boat, (a little hard to do, I do not have a trailer hitch) They will clean the carborators, install an additional in-line fuel filter, and add a can of sta-bil. However this is not a guarantee that it will not happen again. He has seen some engines back in a short period for the same treatment. The charge for this service is approximately $350.00, another $150.00 if he has to pick the boat up.
In their experience in order to keep it running I will have to change the filters often and add sta-bil to the fuel tank on every fill up.

This whole thing should give me a real comfortable feeling when striper fishing out in the ocean during the winter.

Maybe Bombardier can pick up another outboard manufacturer for song real soon.

lenm posted 09-18-2006 06:24 PM ET (US)     Profile for lenm  Send Email to lenm     
I have been having exactly the same experience with my 2003. Only tip I have is to remove the fuel line after each trip and have the engine run until it stalls out, to burn up the remainig fuel in the system. I plan to press Mercury on this issue-I'll keep you posted if I make any progress.
JoeyP posted 09-18-2006 06:35 PM ET (US)     Profile for JoeyP  Send Email to JoeyP     

What dealer are you using in Jersey? I just purchased a 2005 170 with the same motor. It had about 20 hours on it. I bought it from McCarthy's in Brielle. They set me up the same way as you described with the 10 micron filter and stabil treatment. No problem with the the first tank. I just started to use Startron additive. So far so good. I have put about 10 additional hours on the motor and it seems to be ok. I'm just wondering about the colder weather and being out for those stripers too.

Sal A posted 09-18-2006 06:48 PM ET (US)     Profile for Sal A  Send Email to Sal A     
Guys, the Racor in line fuel water separator with the clear bowl is something I'd recommend.

The gunky sludge that you speak of is more curious to me. That sludge is more common on larger boats with large gas tanks, after mixing ethanol fuel with older (MTBE) gas. There have been instances involving clogging. From what I have read, there have also been unfavorable reactions between ethanol and the fiberglass gas tanks. If I were you I'd ask my dealer about that, and also ask them if Pate has come out with a more ethanol-friendly tank (I think they have).

WT posted 09-18-2006 07:27 PM ET (US)     Profile for WT  Send Email to WT     
I want a new motor!!!

Check out the carbureted 2004 90 hp 4 stroke Mercury/Yamaha vs. 2006 90 Mercury "Veradito" on the 170 Montauk hull.

2004 @ 3000 rpm is burning 4.5 mpg.
2004 @ 3500 rpm is burning 5.25 mpg.
2004 @ 4500 rpm is burning 4.5 mpg.

2006 @ 3000 rpm is burning 8 mpg.
2006 @ 3500 rpm is burning 7.77 mpg
2006 @ 4500 rpm is burning 6 mpg.

Improvement at 3000 rpm is 77.8%.
Improvement at 3500 rpm is 48%.
Improvement at 4500 rpm is 33.33%.

Someone check my math.


JoeyP posted 09-18-2006 09:07 PM ET (US)     Profile for JoeyP  Send Email to JoeyP     
Any idea what the new price tag of a 170 Montauk will be with this new "Veradito" 90? I'm sure it will be strictly an option initially, but it has to significantly raise the price.
WT posted 09-18-2006 09:18 PM ET (US)     Profile for WT  Send Email to WT     
I think the 2007 Montauk is around the same price as 2006 and you get a better outboard.
RioRaft posted 09-19-2006 11:19 AM ET (US)     Profile for RioRaft    
My dealer is Island Marine Center in Oceanview NJ. They have actually been great to deal with in every aspect, and I will continue to use them. I just think their hands are tied by Mercury on this one. From the sounds of yours and other posts I better go get the additional filter and carb cleaning done before I am up a creek. I also have a call into Pate Tanks in Fla. I'll let you know what they say.
Barney posted 09-19-2006 10:17 PM ET (US)     Profile for Barney  Send Email to Barney     
Sliding a little off topic but WT started it:

Looks like the 90HP 4-Strokes are getting new competition from Mercury, Evinrude and Honda. The last hold out is Yamaha running the same powerhead as we already have. I don't know about Suzuki.

I've gotten quotes for a new outboard from a couple of dealers in the $9000 range with controls. Heck we've lost three local shops. My favorite shop, the Yamaha dealer Biloxi is not in back in business. The Evinrude dealer around the corner sells everything fast, no need to negotiate.

I'm waiting to change mine I guess. Maybe Yamaha will step up with a new design too.


swist posted 09-20-2006 08:10 AM ET (US)     Profile for swist  Send Email to swist     
As we are often reminded, most folks who post their experiences with this engine do it because they have had a problem, and it's statistically impossible to say what percentage don't have a problem.

So I'll just chime in on as one insignificant data point and say my 2004 carbed 4s-90 has never so much as burped (200 hrs). And it has the worst case usage pattern - couple of runs each weekend and then sits for a week, sometimes two. I do run Stabil all the time and a 10 micron fuel filter. Other than that just normal maintenance. I also have a (2005) Pate tank and the local gas is E10.

And I always forget to pump the primer bulb after it has sat awhile, starts instantaneously anyway.

Not that reading all this stuff doesn't make me wonder if this will all come to an end some day soon....

whaler1234 posted 09-20-2006 05:48 PM ET (US)     Profile for whaler1234  Send Email to whaler1234     
I think you are doing a great job at preventative maintenance (regular usage, fuel stabilizer, 10 micron filter).

My usage pattern was similar to yours when my carbs went south, except my 170 sat idle for 2 mo. treated w/ stabil. At the time, I did not have a 10 micron filter. I think this is the key contributing factor to why I had carb problems recently. Yamaha had fixed their ethanol/fuel related problems by switching from 28-35 micron filters to 10 micron filters.

As for the Pate fiberglass tank, I would suggest calling the manufacturer before you're hit w/ an engine rebuild.

For all fiberglass fuel tank owners, this is a must read.

whaler1234 posted 09-22-2006 09:53 PM ET (US)     Profile for whaler1234  Send Email to whaler1234     
Can anyone tell me what the purpose is for those minuscule in-line fuel filters found inside the fuel lines leading to the fuel pump? (under the cowling, next to the carbs)
These seem redundant to the larger stock fuel/water separators.

Its found in a carbed 2004 Mercury 4 stroke.

This is the first time I've seen this and have never heard any mention of it on any posts.

I'm just wondering if these tiny filters can cause power/fuel problems.

Barney posted 09-28-2006 10:29 PM ET (US)     Profile for Barney  Send Email to Barney     
We are not the only ones, this is from carbed motorcycles from a few years back: carburetors/carburetor%20page.htm
Undaunted1 posted 10-01-2006 12:18 PM ET (US)     Profile for Undaunted1  Send Email to Undaunted1     
Wow, what a lot of discussion about dirty carbs in relatively new motors. Shouldn't we have a reasonable expectation in 2007 to go out, get in our boat and go? Without a lot of tinkering? On a motor the price of a small car no less (which would require no tinkering, by the way)? Good Lord, so boating is a handyman-only sport?

All right, that's off my chest.

OK, so the formulation of gas has changed (10% ethanol, 4 months ago in NJ alone). Could be the 90 Mercs tolerate it less than others. Supplier storage tanks and our own tanks and lines are dirtying up the gas. It will all settle down in time.

If you're not having trouble then cross your fingers, use the Racor filters and additivies and ride it out. If you are and you have a Pate tank, DON'T WAIT, after you get your carbs cleaned the first time, call Pate: (305) 754-0896. If they recommend it, replace your tank with their new ethanol-safe tank or another (don't expect a discount from Pate, they don't view the reformulation as their fault). Replace the lines too.

I went through all this: $3,000.00, for 3x carb-cleaning, one new carb and finally new tank, lines & filter.

Scott in NJ

JoeyP posted 10-02-2006 10:08 PM ET (US)     Profile for JoeyP  Send Email to JoeyP     
What ended up being the cause of your dilema? The Pate Tank,fuel lines or the engine?
Barney posted 10-03-2006 09:24 PM ET (US)     Profile for Barney  Send Email to Barney     
My guess is the Pate didn't help.

Some good news, a positive note for my situation:
The 10 Micron filter, "stabil" fuel additive and the fuel cutoff valve have improved the performance of the outboard. Even after sitting for a month. With some ethanol in todays fuel, I don't think additional fuel system cleaners are necessary. Just my thoughts. Each time I use the outboard it seems to get better and runs very well after a little while. The last time took 5 minutes or so to get running good and it performs better than new. Still takes a little bit, but less of a wait. Running the outboard out of fuel with a slight tilt up to get all the fuel out is key. Starting takes a bit, but always has for mine. Maybe unique. I am hesitant to touch the carbs at this point. Jim

andygere posted 10-04-2006 12:37 AM ET (US)     Profile for andygere  Send Email to andygere     
I was down at my harbor a few days ago, and spoke with a guy who was running a 170 Montauk that looked to be a few years old, with a brand new Mercury 4-stroke 90 on the back (the type that looks similar to a Verado). Long story short, he told me that he had been having the same problems described by Warren for a while, and was unable to use his boat for the entire season. The excellent Mercury mechanic in our town even gave up on it. The final resolution (with help from the Outboard Motor Shop) was a replacement of the engine at no cost. That's right, he told me the problem was escalated up to Mercury corporate, and in the end the put a new fuel injected motor on the boat. The good news for my neighbor at the dock is that he has a new motor. The bad news is that he lost the entire season, and struggled with reliability the year before. By the way, it was his first run with the new motor, but he said he was quite pleased with its performance.
Undaunted1 posted 10-06-2006 07:22 AM ET (US)     Profile for Undaunted1  Send Email to Undaunted1     
Joey P:

To answer your question, no one knows for sure. My opinion is all three conrtributed to the "dilemma", one carb was replaced, so maybe that was the biggest problem.

Runs fine now, but has more trouble starting cold now than it used to, I attribute that to the E-10 fuel and maybe the racor filter. I never used to have to pump the bulb and maybe I have to start doing that now...


swist posted 10-06-2006 07:54 AM ET (US)     Profile for swist  Send Email to swist     
If your fuel filter causes poor cold starting, something is wrong. I have the 10 micron Racor with the same engine and it starts almost instantly when cold, and without squeezing the bulb.
Barney posted 10-09-2006 05:31 PM ET (US)     Profile for Barney  Send Email to Barney     
I went through the carbs today. There was some green gunk on the bottom of the fuel bowls about the size of a pencil eraser. Cleaned each out, blew out everything. The enrichner circuit was clogged, it starts on the bottom of the bowl. Wasn't real hard to get the carbs off and on. Took about 2.5 hours to do the whole job. Also screwed up the throttle to Throttle Positioning Sensor (TPS) lever, ordered it at $2.78.

When I put pressure on the system the OEM filter leaked again. Bigjohn1 said something about an O-ring should be there, I installed one today. I didn't know that there was an O-ring, never saw one when I took the plastic housing off two years ago for the first time. Thought there was a gasket it was on so tight from the factory. I installed one today yes it was just hand tight. The lack of one didn't help mine at all. I was getting lots of air in the fuel system, which I thought was something else.

Thanks to bigjohn1 for being saying something.

Idles great, probably will run great once I get the lever in. Jim

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