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Author Topic:   115-HP Mercury FOURSTROKE Problems
sheikofthesea posted 05-18-2012 02:56 PM ET (US)   Profile for sheikofthesea   Send Email to sheikofthesea  
Hi folks. The [Mercury] 115-HP FOURSTROKE EFI on my 190 Montauk started sputtering last year, and my mechanic added an external fuel filter. This briefly fixed the problem, but at the end of the season the boat was only able putter along at 5-nautical-miles-per-hour. I replaced the external fuel filter this Spring and the boat has no [acceleration from a standing start to plane]. I and or a friend have to sit on the bow. Once we get [the 190 MONTAUK] on plane, I can get [boat speed] up to 22-nautical-miles-per-hour and [engine speed to] 3,500-RPM. Is this a fuel filter problem, a fuel injection problem, a dead cylinder problem, [or] something else? Any help would be appreciated from the Continuous Wave crew.--Sheik
jimh posted 05-19-2012 08:25 AM ET (US)     Profile for jimh  Send Email to jimh     
In order to assess the performance of your boat, I had to compare it to the performance that Boston Whaler reports for a similar boat. I looked on WHALER.COM and found this report: EnginePerformance/268455_EnginePerf.pdf

That report shows a top speed of 40-MPH (or 34.7-nautical-miles-per-hour) for a 190 MONTAUK and a 115-HP engine. You report a top speed of only 22-nautical-miles-per-hour. The ratio of your speed to the Boston Whaler factory speed is

Your Speed/Published Speed = 22/34.7 = 0.634

We know that boat speed is proportional to horsepower-to-weight by the 0.5 exponent, so we can infer the horsepower you are getting by taking your speed ratio and raising it to the exponent 2:

0.634^2 = 0.4 = Your-HP/Published-HP

Now we infer your engine's power ouput as 0.4 x 115 = 46-HP

There is clearly something wrong with the engine.

Since you report that you have already had significant problems with the fuel delivery on your boat, it seems reasonable that the first area to investigate would be the fuel system. I would also check the engine spark system to verify that all cylinders are getting spark. Use an in-line spark checker to verify spark.

Marlin posted 05-21-2012 10:00 AM ET (US)     Profile for Marlin  Send Email to Marlin     
I don't know what version of the 115 you have, but my 2003 115 four-stroke (the older version with the Yamaha powerhead) also has an engine-mounted filter cartridge on the aft port side of the engine.

Perhaps more to the point, a friend of mine was having similar-sounding fuel delivery problems with his 190 Nantucket a few years ago. After a lot of investigating, he found that the end of the fuel pick-up tube inside the tank was improperly formed (I think it was kinked, but I forget the exact details) which caused it to occasionally restrict fuel flow with similar results to yours.


Phil T posted 05-21-2012 02:20 PM ET (US)     Profile for Phil T  Send Email to Phil T     
Bob is referring to Henry a.k.a. the Yiddil.

Sheik- When advancing the throttle, does the engine sound change to a labored or bogging sound?

If your motor is EFI, it could be clogged fuel injectors.

L H G posted 05-26-2012 02:06 PM ET (US)     Profile for L H G    
A 190 Montauk is a fairly new boat, so take the boat in for engine warranty service.
Whalerdog posted 05-31-2012 09:20 PM ET (US)     Profile for Whalerdog  Send Email to Whalerdog     
Check the pickup in your tank mine an 07 Montauk 19 with Merc 115 is doing the same thing I will pull the pickup this weekend. There is probably a screen that needs cleaned.
Whalerdog posted 05-31-2012 09:22 PM ET (US)     Profile for Whalerdog  Send Email to Whalerdog     
Ethanol in fuel I heard can clog the screen I was told. I didn't use the boat as much as usual last year. It sputtered to the dock. Ran fine on the gas oil mix when I winterized it from a 2.5 gallon can.
Whalerdog posted 06-17-2012 02:06 PM ET (US)     Profile for Whalerdog  Send Email to Whalerdog     
Can't really get my arm in to pull the pickup.
Whalerdog posted 06-17-2012 02:07 PM ET (US)     Profile for Whalerdog  Send Email to Whalerdog     
May be there is a check valve as I can't blow back into the tank. It may have clogged.
tmann45 posted 06-17-2012 02:43 PM ET (US)     Profile for tmann45  Send Email to tmann45     
There should be a check valve (anti-siphon valve) at the top of the pickup, usually the pipe to hose barb, which would prevent blowing into the tank.

Also, there should NOT be a screen on the bottom of the pickup. Yes, I know that is still being done, but it does not make any sense to plug up your fuel line assembly in a place that is not readily accessible. I just disassembled a very high quality Quicksilver brand 6-gallon plastic tank for cleaning that I bought in the mid 90's and it had a screen on the bottom of the pickup tube. I also have a few year old Moeller 12-gallon under seat tank for my 13 that has a piece of screen wrapped around the bottom of the pick tube held on with an o-ring (?), if I could get to it, I would remove this screen.

sheikofthesea posted 06-22-2012 02:36 PM ET (US)     Profile for sheikofthesea  Send Email to sheikofthesea     
[This article was originally posted to another discussion but it belongs here, and I have moved it.--jimh]

As always, thanks for your ideas. The [cause of the] problem [with poor running of the Mercury FOURTSTROKE 115-HP outboard engine] has been diagnosed as bad fuel. [Unclear] wants me to take the boat out of the water, to their shop, to pump out the fuel (at a high price).

Is there any way I myself can efficiently, effectively, economically, safely, and without pollution [pump out the fuel]? Once I get the fuel out, are there any further steps I have to take before filling up [the fuel tank] with clean new fuel? Thank you for any help you can give.

tmann45 posted 06-22-2012 09:43 PM ET (US)     Profile for tmann45  Send Email to tmann45     
Get the cheapest 12-Volt fuel pump from an auto parts store. Go to Lowe's or Home Depot and get some speaker wire and a toggle switch, and some clear vinyl hose to fit the pump. Hook it all up and attach to your battery. Attach to your fuel pickup or stick down the fuel fill (don't know what tank you have), and pump it out into 5-gallon cans. Just make sure the switch is not around any fuel vapor or get an explosion proof/intrinsically safe switch. I just got finished doing this on a friend's boat last month, pumped out 120 gallons and he gave it away to his neighbors.
jimh posted 06-23-2012 09:40 AM ET (US)     Profile for jimh  Send Email to jimh     
I am glad you found the problem. Of course, there is no warranty coverage for running the engine on bad fuel. I don't think you can seek a remedy under the manufacturer's warranty against defects in original manufacture of the engine.

Disposal of a large volume of gasoline could be a problem. If you do succeed in removing the gasoline from the fuel tank, how to you propose to get rid of it?

conch posted 06-23-2012 10:37 AM ET (US)     Profile for conch  Send Email to conch     
In my area of south Florida, vendors who offer fuel polishing services will dispose of bad fuel if you have (pay) them to pump it out.

Might want to check into that.


Whalerdog posted 06-24-2012 05:22 PM ET (US)     Profile for Whalerdog  Send Email to Whalerdog     
I am now thinking I have a fuel pump problem. No water in the fuel and I launched it today only to barely make it back. Now I can't get it running in the driveway to flush it.
Jefecinco posted 06-25-2012 09:14 AM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     

If you have a primer bulb in your fuel line use it to pump fuel to your engine when it begins to slow or sputter. If you don't have a primer bulb consider installing one. They are useful to move fuel from the tank and as a fault analysis tool. I believe there is an article in the Reference Section that discusses the usefulness of primer bulbs.

If squeezing the primer bulb results in your engine running better there is a good likelihood that your engine mounted fuel pump is defective.

Fuel delivery problems can also be caused by leaks on the suction side of the system which allow air to enter the fuel lines and pumps. This results in fuel starvation with symptoms similar to those caused by fuel pump and or filter problems. You reported that you replaced the fuel filter (element??) this Spring. If you replaced the element you may have crimped the element O-ring. If you replaced the filter assembly you may have leaks at the inlet or outlet fittings. If the primer bulb suggestion is not helpful consider checking the filter.

I'm not familiar with your engine so the above is guesswork. Some engines have both a transfer pump and a lift pump so that may also enter into your analysis.

Good luck.


Phil T posted 06-25-2012 09:57 AM ET (US)     Profile for Phil T  Send Email to Phil T     
I agree with Butch.

EFI engines have 2 fuel pumps. A lift pump (low pressure) and a second pump (high pressure) inside the vapor seperator tank (VST).

tom976 posted 06-25-2012 11:34 AM ET (US)     Profile for tom976  Send Email to tom976     
If you have questionable fuel in the system you need to get it out of the vst tank. (drain it)

From there you can prime in fresh fuel and give it a go.

If your gas looks like apple cider, it has some water in it and is going south. If it starts to seperate then you need to get that pure ethanol out along with some water.
(just put some gas from the boat in a glass or good plastic container and let it sit for a few minutes)

From there, I put in a product called isoheet. (2 bucks from Walmart a little more at most autopart stores)

It takes gas that looks like apple cider and makes it looks like apple juice. I dealt with the problem last year and just again yesterday while heading out fishing. UGGGHHH. I was able to get back to the dock, get some isoheet and off I went fishing for the day. Either I am getting bad gas at the dock or water is getting into my tank. I dont work for the company that makes the stuff, I just bought a bunch of different fixes in a bottle (seaform etc) and found one that worked for me.

Whalerdog posted 06-27-2012 08:11 PM ET (US)     Profile for Whalerdog  Send Email to Whalerdog     
Thanks guys. Fixed today it was the lift pump. I think I'll put a primer ball in if I find an easy spot. I'll have to look in the morning. I guess easier if I ran out of gas to re-prime.
jimh posted 06-30-2012 05:43 PM ET (US)     Profile for jimh  Send Email to jimh     
How many hours of running time does your Mercury 115-HP FOURSTROKE outboard engine have? I don't think this engine is very old. To have a failure of the fuel lift pump seems odd.

Is Mercury replacing the fuel lift pump under the original warranty of the engine? In other words, does Mercury think the fuel lift pump was defective in its original manufacture?

Whalerdog posted 07-01-2012 09:25 AM ET (US)     Profile for Whalerdog  Send Email to Whalerdog     
It has 319 hrs. Now it runs but it does run right. I put an impeller in last year and only put 50 hrs on it or less. It never took in any sand or anything to damage it. It is always flushed for 7 + minutes when I return. Now when I launched today buzzer is going off and pressure seems low. Then motor started dying again when I hit it for over 60 seconds. Not a good season that already started late. Between BW not being able to make a cockpit that drains I joyfully get to look at moldy seams I am sick of this boat. Re-did the seams last year and it is the same crap again in the rear and in front of console.
wezie posted 07-01-2012 11:59 AM ET (US)     Profile for wezie  Send Email to wezie     
Whalerdog, I am not picking on you.
This string is confusing, at least to me.

Did you ever look at the fuel or drain it?
Pump some of it into a glass container and see what you have?
The under cowl filter may tell you enough.

In my opinion that is the most likely problem in this age of Federal garbage gas.

The pump may have been some the problem, but if the gas is bad, well?
The pump may have been done in by the gas.

When we hook up the trailer and launch, and take off, we are shaking up all the gas and whatever is in it.

The suggestions about the fuel pickup tube are also valid.
Alcohol could have eaten it, or part of it.
And access was not a thought when these things were designed.

Whalerdog. do you have the factory manual for the engine?
My '05 90 carb manual shows a teenee filter in front of each carb.
The injected one may have something like this?

And I have to remove the intake manifold if I want to get to them.
Access was not a thought.

And I could be totally wrong about your situation.

Good Luck!

Whalerdog posted 07-01-2012 12:40 PM ET (US)     Profile for Whalerdog  Send Email to Whalerdog     
Gas looked good, tested it for water negative. I looked in tank with a light and it all looked good. I pulled the sender in the tank. Changed both fuel filters. I do think it needed the pickup pump as it would not even run before.

Warranty is toast on this motor at 6 years old.

I don't think on an 07 the alcohol could or should have eaten pickup. I would be disappointed if that is the case. I know from racing Skaters the earlier ones had fuel tank issues but this is an 07. 30 gallons of new fuel in it this morning and it was only 1/4 full.

Water pressure is seemingly down so I have to address that first. I don't feel like doing a water pump today. Mech is off tomorrow so then there is Tuesday and then the 4th so I guess I will be SOL. I feel like wrapping it up and the season never even started.

The Whaler next to me has some old Yamaha engine on it and it runs fine for years. Everything new seems to really be a POS from appliances to tools. Just made to get you out the door and work for a year. I am seemingly surrounded with stuff 2-3 years old with nothing but problems. This just tops it off. I want to get trailer out of driveway and now I look out the back door and see a boat I can't use.

The most important thing is to take my dog for his canal rides. He was all excited and howling when he saw the boat in the water. He was going nuts watching me prep it the past few weeks out through the front door. This morning he jumped in it only to go no where. I'll leave it in the water for the mechanic to run it.

Thanks for the help all!

Will keep you posted.

Whalerdog posted 07-01-2012 12:46 PM ET (US)     Profile for Whalerdog  Send Email to Whalerdog     
To not design easy access for service is a failure.
Whalerdog posted 07-02-2012 05:06 PM ET (US)     Profile for Whalerdog  Send Email to Whalerdog     
Now thinking water pump failure is putting engine in limp mode. Will put one in tomorrow and post up the results. I guess they have a limp mode? Pressure is low in any case.
Whalerdog posted 07-07-2012 10:06 AM ET (US)     Profile for Whalerdog  Send Email to Whalerdog     
Thermostat housing was shot so it would stay open at low RPM. The engine needs lower bushing and upper mounts. Will get it back in water and see how fuel pressure is while running with a gauge.
Whalerdog posted 07-13-2012 05:24 PM ET (US)     Profile for Whalerdog  Send Email to Whalerdog     
all fixed with new mounts now the motor does look like a bobble head on the transom.
boatdryver posted 07-18-2012 12:14 PM ET (US)     Profile for boatdryver  Send Email to boatdryver     
you hate the boat so much maybe you should get another, older boat with a smaller old 2 stroke carb'd motor


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