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Author Topic:   Fuel Filters
billh1963 posted 02-22-2004 11:00 AM ET (US)   Profile for billh1963   Send Email to billh1963  
I would like to install a fuel/water filter/separator on my Montauk. I've been searching the archives and tried to resurrect a thread that had some information but when I replied to it the thread didn't show up [Huh?--jimh]

I would like to get a quality filter of small size with a clear bowl and think I want to go with something like this mounted on the transom in the splashwell.

Is there an ultimate recommendation on one that fits good in that area of the boat? Also, is the final word to mount the bulb betweeen the filter and the engine? There seems to be some debate on this topic.


kingfish posted 02-22-2004 11:25 AM ET (US)     Profile for kingfish  Send Email to kingfish     
Not much debate, I don't think - bulb should be the last thing in the fuel line before the engine, within 2 feet or so if possible, and vertically oriented if possible. Lots of other scenarios work, but this is the optimum.
Sal DiMercurio posted 02-22-2004 12:02 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
If you want to install the best filter, get a Racor.
I prefer the outboard filter with the clear bottom so you can see if theres water or debrie in the filter & just drain it out from the petcock at the bottom.
That filter comes in three sizes, one that fits the Racor head, one that fits Mercs head and one that fits OMC/BRP head.
They only fit the head that matches so don't think it is universal and fits all.
The Mercury screw-on portion has a larger diameter female screw in then the OMC/BRP and the Racor is another size.
They are all [made by Racor] and the same quality, but different size female fittings so be sure you get the correct replacement when it's time.
John O posted 02-22-2004 12:22 PM ET (US)     Profile for John O    
Sal, Are you saying that I can replace my Mercury/Quicksilver filter with a Racor which I would prefer?
Buckda posted 02-22-2004 12:23 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Trailer Boats Magazine just had a feature on this in either the February or March issue. Run out to Wal-Mart to see if they carry it - it should help you decide brand/type.


jimh posted 02-22-2004 01:08 PM ET (US)     Profile for jimh  Send Email to jimh     
Many boaters live happy lives just using inexpensive water-fuel separating filters like the Mercury or Tempo brands, but some like to go the extra dollar and get the RACOR filter with the clear bowl on the bottom.

A middle course is to use the mounting bracket/fuel manifold from Mercury or Tempo and get the first replacement filter from RACOR with the bowl. Here is why:

The Mercury or Tempo mounting bracket/fuel manifold has four ports, two inlets and two outlets, so it works well with dual tank feed lines and dual engines. The RACOR manifold only has three ports. (I am not sure how they are arranged, either as dual inlets/single outlet or vice-versa.) It is not as versatile in a dual tank or dual engine situation. Of course for the really cautious, you'd get dual filters so the manifold problem would not be a concern.

There is also a stainless steel mounting bracket/fuel manifold available, too, and that is recommended for salt water use if the assembly is mounted in the open splash well or cockpit. I think that comes from TEMPO.

You can use the $7 replacement filter from Mercury or you can go with a more expensive $25 RACOR element that is sized to fit the Mercury manifold. I'd recommend the Mercury manifold because you are going to be able to buy some filter element to fit it just about anywhere on the planet. If you get something more exotic you won't find the replacement element at WALMART when you need one in a hurry.

The RACOR filter is nice because you can see the water that has been accumulated in it and filtered out. It can be drained and discarded. Perhaps you can keep using the filter longer without discarding it. I think once you get the plastic bowl you can just buy the elements, too, and save money.

The disadvantage of the plastic bowl is it can break. I don't know if it meets all the regulations for inboard boats or not when used with gasoline. I think it does for diesel.

As for where the primer bulb ought to go, that is a matter of some discussion, but ironically while you were posting this article I was just finishing a reference article on that topic, so please visit it for my opinion.

It has been seen that the primer goes before the filter, notably here:

but I'll leave that to another debate to decide.

lhg posted 02-22-2004 01:28 PM ET (US)     Profile for lhg    
The Racor filter separates out an additional 1% water over the engine brand & aftermarket spin-on filters for them, for 3 times the filter replacement cost, and much higer initial cost. It's a lot bigger and more unsightly too. You decide. I've been using the Mercury brand for 20 years now, and not a single problem with engine performance. Do we really believe that a major engine manufacturer like Mercury would put out a junk filter, thereby trashing their engines? Leave Racors for the diesel they were originally invented for unless you've got money to burn instead of gasoline..
John O posted 02-22-2004 01:31 PM ET (US)     Profile for John O    
Great feedback--------thanks


billh1963 posted 02-22-2004 02:09 PM ET (US)     Profile for billh1963  Send Email to billh1963     
I've ordered the Racor filter although I agree with what lhg is saying. I remember and trust the Racor name from my commercial fishing days when working on my Dad's shrimpboat in SC. We used a Racor filter for the 6-71N engine and then later on 8V71's and a CAT3408. Name brand loyalty is a hard thing to break!

Now that I am older with kids I try to buy the best possible equipment when it comes to safety and reliability [SOSpenders, Racor filter, Boston Whaler :-) ]. Even though other filters will work great I will feel better with a Racor in the boat!

jimh...when I replied to the post this morning the time stamp was stamped for 2000...

Thanks, everyone!

jimh posted 02-22-2004 05:43 PM ET (US)     Profile for jimh  Send Email to jimh     
Bill--There is a well know glitch in the current software that causes an error in the year seen in postings. You revived a four-year old message thread, and your new article was added--it just got the wrong date stamp.

It is really not a good idea to revive four-year old threads, anyways.

Peter posted 02-22-2004 07:51 PM ET (US)     Profile for Peter  Send Email to Peter     
Jim, are your twin engines rigged to draw fuel through a single filter? Seems to me that would not be a desirable set-up for a variety of reasons, including the possibility of one engine competing with the other engine for fuel causing the weaker one to starve.

Both of the manifolds on my 27 have the four port arrangement so they must be OMC or Tempo manifolds, not Racor. The thought never occurred to me that the four ports were provided to enable twin engines to be connected to a single filter or separate tanks. I always thought the four port arrangement was provided to allow mounting flexibility for the manifold by providing flexibility in plumbing, i.e., (1) in and out from the left, (2) in from the left out from the right, (3) in from the right out from the left, or (4) in and out from the right. While I suppose two engines could be connected to this filter or two fuel tanks or both tanks and engines, I think it would be downright stupid not to have each engine draw fuel through its own filter and separate fuel line just to save 40 dollars initially and then 7 to 14 dollars per season for the extra replacement filter element.

I've used the Racor filter with the clear blue plastic bowl for years and that plastic is very tough. You'd really have to hit it hard with something heavy to break it.

wetdogsoup posted 02-22-2004 09:27 PM ET (US)     Profile for wetdogsoup  Send Email to wetdogsoup     
Is it good to have a water filter/separator even for the smaller engines (merc 60/2)?


Sal DiMercurio posted 02-22-2004 09:55 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Jim, no the clear plastic bowl filter CANNOT be used on inboard applications, it's for outboards only. Only the solid metal case filter can be used on inboards, because a fire would burn right through the plastic in a covered engine room, where the outboard application is always with an outside fuel line and filter. Yes the yellow plastic see-through is for diesels engines while the blue see- through plastc is for outboards.

For as much as the Racor head costs, you would think they would use a paint or sealer that wouldn't oxidize in 8 months and peel off. Had to sand mine down, prime it with Krylon, paint it because it looked about 30 years old--it was only 6 or 8 months old.
John O, yes Racor makes the same filter that fits your Merc head as the one that fits theirs, just be sure you get the right one.
You must buy a Racor filter in order to get the one that allows the blue plastic bottom to screw on. When it comes time to change that filter, you will need 2 filter wrenches to get the plastic bottom free from the old filter

jimh posted 02-23-2004 08:29 AM ET (US)     Profile for jimh  Send Email to jimh     
At the moment on my rig the water separating filter is a single point of failure in the fuel system. It has two inlets from two tank pick-ups, and two outlets for two motors. Separate filters would be better--maybe a project this spring.
John O posted 02-23-2004 09:19 AM ET (US)     Profile for John O    
Thanks Sal. While more expensive, the clear bowl sounds like a good investment. What is the reccomended time period or hours to change a filter? Once per season in the Northeast? Last season I put on 60+ hours on my 75hp Merc. This year I plan to use it significantly more.
Sal DiMercurio posted 02-23-2004 11:46 AM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
I change mine every year & put between 250 & 300 hours per year on the engine.
If you have an older boat with a built in tank thats starting to rot, i'd change the filter more often.
I'm using a ploy tank right now & it's far cleaner then the aluminum older tank.
I'v got to replace my belly tank & "not" looking forward to it.
quattro20vt posted 02-23-2004 01:02 PM ET (US)     Profile for quattro20vt  Send Email to quattro20vt     
Peter brings up a good point on the potential for twin engines competing for fuel from a single feed. This was brought up to me by my dealer when I repowered recently, concerning the feed for my kicker--not an issue for me as the kicker draws from the second pick-up from the main tank.

As explained to me, the issue is not so much starving of fuel if both engines are running, but the risk that if one engine is off, the running engine may draw from the stopped engine's feed line. If there is any break in the fuel line or a defective (leaking check valve in the) primer bulb, this is a possibility. Then, when you go to start up the stopped engine, you'll have either to reprime or worse, an airlock of some kind. For a carb'd engine, not a big deal, but for a FI engine, could be problematic. Where a single pickup feeds a main & kicker, some kind of check valve is to be installed in each engine's feed, after the lines split.

Also as Peter notes, the fuel/water filter head I have (Mercury kit, p/n 35-802893A 4) has four ports, configured for in/out from either side, apparently for plumbing flexibility, not necessarily to feed two motors from the single filter.

One other item--Mercury's instructions on the Optimax are to remove any fuel flow restrictions such as external fuel/water sep filters or shut off valves. The Opti 225 (and the old Laser EFI) have under-cowl fuel/water sep filters wired into the alert systems. Annual replacement is recommended. On installation, the dealer removed the original external fuel/water filter and plumbed direct to the pickup. I'll use fuel/water filter for my kicker going forward.

lhg posted 02-23-2004 08:49 PM ET (US)     Profile for lhg    
When I rigged up my twin Merc 115's back in 1986, (on 18 Outrage) I called the factory regarding water separating filter needs. First of all I was told that Merc's filter, at least, can process a 60 GPH flow rate. Secondly, there was no way the twin in-line 6's could use that much fuel, so they told me to use one filter for both engines, and that the filter is designed for that capability with the four fittings. In addition, the 18 outrage has a dual take off fuel manifold, so I plumbed two hoses into the filter head also. So on mine, all four ports on the Merc filter are being used. All the filter really does is provide another "pool" of fuel, similar to two withdrawls out of the tank, from which the engines draw. In 18 years of operation, I have never had a fuel withdrawl/starvation problem. One engine does not rob fuel from the other, even with only one operating.

As for JimH's comment that this provides a single failure point, that's easy to overcome by carrying a replacement filter, which I do. The Merc filters are small, economical to buy and easy to stow. A water separating filter is really a quite simple device.

On my 200 EFI's, I have rigged a separate filter for each engine, because of the higher potential fuel draw. Even here, however, I don't come close to the 60 GPH maximum capacity, except perhaps running wide open for an hour, which I don't do. And when you have two filters, you need to carry TWO spares, since gas is coming from a common tank. So the real only issue is GPH flow capability of your chosen filter. Only use two if you absolutely have to.

John W posted 02-23-2004 09:11 PM ET (US)     Profile for John W  Send Email to John W     
Jim & lhg, I have a simple (stupid) question regarding connecting two fuel tanks to ONE engine. The '71 Outrage I'm restoring will have two tanks under the quarter decks (it previously had only one central tank). I need to feed the engine from two tanks, and am confused as to how to connect them. Would connecting them via the two inlets on a fuel filter mounting be a good or bad idea?

I am looking at brass fittings in the West Marine catalog designed to connect two these fittings require you to run off of one tank or the other? Or do they allow you to run off of both tanks at the same time? I would like to run off of both tanks at the same time if this is possible, assuming the tanks would remain evenly full. Can someone help me with the best way to hook two tanks to one engine?



lhg posted 02-23-2004 09:49 PM ET (US)     Profile for lhg    
For above deck, separately vented tanks, I think you have to have a Tempo selector valve, drawing out of only one at time.
Peter posted 02-24-2004 08:28 AM ET (US)     Profile for Peter  Send Email to Peter     
Larry, what if you have an obstruction in one of the two fuel feed lines to the single filter? Both engines are then drawing through a single feed line and depending on engine size I suppose you may have a situation where neither engine can get enough juice or you have an excessive vacuum build. Also, in theory higher fuel flow rates through a filter means more frequent filter changes so there really isn't any savings by running through a single filter.

To the extent that the filter is a single point of failure, it will shut down both power plants, not just one. That could be a significant problem in some operating situations than if just one engine shuts down due to a filter failure. In my view, using a single filter in a twin outboard application cuts against the redundancy philosophy of twin outboards. Of course, if you take the redundancy philosophy to the extreme, you should also have dual tanks.

John, I wouldn't run a single engine off both tanks simultaneously. Every boat that I know that has multiple tanks has a selector valve. For example, my 27 has three tanks and has two three-way selector valves so that both engines can draw from any of the three tanks, but only from one tank at a time. My friend's 27 Grady has two tanks and two two-way selector valves, same plumbing arrangement, the engine can only draw from a single tank at a time.

jimh posted 02-24-2004 09:10 AM ET (US)     Profile for jimh  Send Email to jimh     
Sometimes you can make things too complex.

You could argue that with dual engines, dual filters, and dual feeds (from a common tank), you ought to construct a manifold and valve arrangement so that each feed could supply either filter, and also allow each engine to draw from either filter output. With this arrangement, you could keep both engines running even if one filter or one tank feed went bad.

But then the single tank is a point of failure, so I better get dual tanks and each with dual feeds and dual filters in a manifold so I could run either or both engine from any combination of tanks, feeds, and filters.

At some point, it is reasonable to keep it simple.

I know a fellow with a fancy diesel installation with two tanks, (port and starboard tanks), and a fancy fuel distribution system that switches the feeds and returns. (His diesel engine draws much more fuel than it actually uses and returns unused but filtered fuel back to the tank.) He got all these valves confused and ends up drawing fuel from one tank but returning it to another. Pretty soon he has one tank going way down and one overflowing. Big mess ensues.

Peter posted 02-24-2004 09:32 AM ET (US)     Profile for Peter  Send Email to Peter     
I guess I take the view that its better to have one single point of failure than two single points of failure particularly if its easy and cheap to eliminate one of the two single points of failure.
John W posted 02-24-2004 09:00 PM ET (US)     Profile for John W  Send Email to John W     
lhg & Peter, thanks for the responses. I called Tempo & you're right, I can't connect the two tanks as one, and instead need to run off of one at a time using a switch.

Thanks again,


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