90-HP Engine Falls Flat at Full Throttle

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
upstateNY
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90-HP Engine Falls Flat at Full Throttle

Postby upstateNY » Fri Aug 04, 2017 11:41 pm

[A 90-HP engine] has been sitting for couple of years. [A 90-HP engine] fired up and ran well on muffs in the driveway. On the river [a 90-HP engine] has great acceleration, but falls flat at maximum throttle after a few seconds; yet it runs well at half-throttle and idles okay. Here is a youtube video of the [engine]. Thanks for input.

https://youtu.be/xHUjbf6Hcxg

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Phil T
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Re: 90 HP Engine Fall Flat at Full Throttle

Postby Phil T » Sat Aug 05, 2017 8:17 am

Fuel supply. Open the vent on the tank.
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upstateNY
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Re: 90 HP Engine Falls Flat at Full Throttle

Postby upstateNY » Sat Aug 05, 2017 1:16 pm

I was using a Evinrude six-gallon tank and there is no vent. The fuel line is 5/16. That [may be] the [cause of the engine not being able to run at full-throttle]. I am going to get a length of 3/8 fuel line and try the 24-gallon tank I have. I just grabbed the Evinrude as it had fresh fuel and was sitting in garage handy.

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Phil T
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Re: 90 HP Engine Falls Flat at Full Throttle

Postby Phil T » Sat Aug 05, 2017 1:58 pm

If the tank it the old 6-gallon metal tank I see in the right side of the video, the fill cap can be loosened 1/4 turn to vent.
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jimh
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Re: 90-HP Engine Falls Flat at Full Throttle

Postby jimh » Sat Aug 05, 2017 2:06 pm

The most likely cause of the 90-HP engine losing power at full throttle after a short time at that setting is due to loss of fuel, likely caused by a restriction in the fuel supply or a marginal fuel lift pump. As suggested, check the fuel tank vent to verify it is open. A fuel hose with an inside diameter of 5/16-inch should be adequate for a 90-HP engine. A bad primer bulb could be another source of fuel restriction. Are there any in-line fuel filters involved?

jhomeister
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Re: 90-HP Engine Falls Flat at Full Throttle

Postby jhomeister » Sat Aug 05, 2017 7:45 pm

Is this phenomenon reproducible after sitting a while? Seems to happen very quickly to be generating a vacuum in the tank. Another source of fuel line restriction to consider is deteriorating and sloughing hose lining due to ethanol-induced damage. What is the hose vintage? Check the fuel filter for pieces of hose lining and/or cut the line just before the filter/engine connector/fuel pump (first in-line accessory) and check for blockage.

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Re: 90-HP Engine Falls Flat at Full Throttle

Postby jimh » Sat Aug 05, 2017 8:11 pm

Here is a youtube video of the [engine]. Thanks for input.


A little input on making motion picture recordings: hold the camera properly.

SAY NO TO VERTICAL VIDEO! VERTICAL VIDEO SYNDROME IS DANGEROUS!
https://www.youtube.com/watch?v=Bt9zSfinwFA

upstateNY
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Re: 90-HP Engine Falls Flat at Full Throttle

Postby upstateNY » Sat Aug 05, 2017 10:24 pm

Thanks for all the input. I picked up a length of 3/8-inch inside diameter fuel hose and new in-line filter attached to the 24-gallon fuel tank. Problem is resolved now.

Whalerfisherman
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Re: 90-HP Engine Falls Flat at Full Throttle

Postby Whalerfisherman » Tue Sep 12, 2017 11:44 pm

I have a similar problem with a 2007 four-stroke-power-cycle electric fuel injection 90-HP, except [the problem] just does occurs at start up. It occurs about three times then clears up.

Any ideas?

I changed fuel line and filters.

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Re: 90-HP Engine Falls Flat at Full Throttle

Postby Whalerfisherman » Wed Sep 13, 2017 9:52 am

upstateNY wrote:Thanks for all the input. I picked up a length of 3/8 fuel line and new inline filter attached to the 24 Gallon Attco fuel tank. Problem is resolved now.


What was [the cause of] the problem?

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Dutchman
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Re: 90-HP Engine Falls Flat at Full Throttle

Postby Dutchman » Thu Sep 14, 2017 9:46 am

The [problem under discussion in this thread is] probably the same problem I had on my 2008 Mercury 60-HP FOURSTROKE: deteriorating hose(s) due to the ethanol blended in non-marine gasoline. See images below.

https://photos.google.com/photo/AF1QipOD0Hb0d-MZ4o0Xu7-5XYMJYACw21UTN9n29Qy_

https://photos.google.com/photo/AF1QipPyGlVje7g-SUfEhAvjsNDG0EOxCo104_7GZPBp

New, same-size, better-quality hoses, new filter, and flush solved the problem.

[Note: as revealed later, the problem under discussion was not caused by deterioration of the fuel hose due to ethanol-gasoline blended fuels--jimh]
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upstateNY
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Re: 90-HP Engine Falls Flat at Full Throttle

Postby upstateNY » Mon Apr 09, 2018 12:00 am

I am sorry I have not been on in a while and did not realize I had a question pending.

When I was testing the boat, I was using an old, metal, 6-gallon fuel tank because on the [24-gallon] tank I previously used the fuel line was brittle. The problem [of the 90-HP engine running out of fuel at high throttle settings on the 6-gallon tank] was resolved by using the [24-gallon] fuel tank [and installing new fuel hoses and primer bulb as mentioned above].

I was still having problems with the engine stalling at idle. I rebuilt the 90-HP engine's fuel pump with new diaphragm and gaskets, but still had the same problem.

I finally figured out the idle stalling was caused by the pickup tube in the [24-gallon] fuel tank. Under load [the engine] would draw fuel fine, but at idle it was not. [The fuel pickup] is just a plastic tube that fits in a sending unit. I fixed the tube in place, and the engine runs and starts better than it ever has before.

Again sorry for the delayed response.

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Re: 90-HP Engine Falls Flat at Full Throttle

Postby jimh » Mon Apr 09, 2018 9:43 am

Thanks for the follow-up posting. To learn the exact outcome and the details of the solution to a problem is always interesting. Thanks for sharing this useful information.

It seems that all the problems with the 90-HP engine were external to the engine and caused by defects in the fuel supply system.

Finding the remedy to the problem with poor fuel supply at engine idle speeds in the 24-gallon fuel tank was quite an accomplishment. Perhaps there was an air leak in the plastic pickup tube where it fitted to the manifold at the top of the tank. When there was a high suction from the fuel pump, perhaps the tube itself became sucked into a better fit into the manifold, and the leak was sealed off.

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Re: 90-HP Engine Falls Flat at Full Throttle

Postby Whalerfisherman » Mon Apr 09, 2018 12:51 pm

I appreciate [user upstateNY] getting back to [the forum and posting the details of the solution to his problem that revealed the cause was completely external to his engine and was in the external fuel system--jimh]

I was having problems with [my 2007 90-HP four-stroke-power-cycle engine] losing power on the initial start-up to plane at the beginning of the day. [My 2007 90-HP four-stroke-power-cycle engine] would run the rest of day without problem.

I had [my 2007 90-HP four-stroke-power-cycle engine] hooked up to a computer. The engine is at 130-hours currently

The [fuel] lift pump had stopped working at 40 hours.

The high-pressure [fuel] pump was overheating.

I replaced the entire fuel supply module--very easy--and my problem was fixed.

[I was] surprised the high-pressure pump was able to draw fuel from my tanks [after the fuel lift pump had stopped working].

Thanks again [to user upstateNY who described how the solution to his problem was not in the engine at all but in the fuel tank external to the engine].

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Re: 90-HP Engine Falls Flat at Full Throttle

Postby jimh » Mon Apr 09, 2018 4:41 pm

WHALERMAN--thanks for adding to this thread by describing your problem with your 90-HP four-stroke-power-cycle engine stalling at the beginning of the day, and how you were able to find the cause in the engine itself and in its failed fuel pumps, rather than a problem external to the engine in the fuel tank and tank pickup, and how you were able to remedy the problem by a complete replacement of the entire fuel module.

Because the cause of your problem was from failure of the fuel lift pump in the engine, which is quite a different cause than the problem under discussion in the original post, please mention the brand of engine. Knowing what manufacturer and model engine will be useful information to have.

It seem rather unusual to me that the lift pump would fail and the entire engine fuel module of an outboard engine would have to be replaced after only 40 to 130-hours of operation of the engine. For many people, that amount of engine time is less than one season of use. One would hope that with a new engine the entire fuel module and the fuel lift pump would last longer than that.

Because the solution to your problem required replacement of the engine's entire fuel module, can you tell us how much did it cost to have the entire fuel module replaced?

Was there any warranty on fuel module provided by the manufacturer?

How old was the engine in terms of model year and number of years it had been in use?

Were you using gasoline fuel that was blended with ethanol as the routine fuel for the engine?

Were you buying the fuel on the highway or at marine fuel docks?

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Re: 90-HP Engine Falls Flat at Full Throttle

Postby Whalerfisherman » Mon Apr 09, 2018 5:57 pm

I bought the boat and engine used. The engine is 2007 Mercury 90 FOURSTROKE EFI--yes, EFI model.

For an engine that is 11-years-old, it has very little running time hours. It's in perfect shape.

The 2008 Boston Whaler boat was just as clean.

I assume the fuel is still soaking into seals and gaskets breaking them down, regardless of pump operation.

The fuel system module was $800.

I buy fuel mostly on land.

Yeah, I put about 60 hours on the engine since I bought it last year.

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Re: 90-HP Engine Falls Flat at Full Throttle

Postby jimh » Mon Apr 09, 2018 6:20 pm

When buying fuel for a boat on the highway, avoiding ethanol-gasoline blended fuels can be hard, although it depends what part of the country you are located.

Here in Michigan we are still suffering from the legacy of our former governor, former policital talk-show host, Jennifer Granholm. During her administration the labeling of fuel at highway retail fuel stations was changed to provide a disguise for ethanol-gasoline fuel by removing a former state regulation that such blended fuels be clearly labeled at the fuel dispensing pump. We are still living with the legacy of the pro-Ethanol lobbying, and even now--15-years later--when you buy gasoline on the highway in Michigan you can't tell for sure what you are getting. The best assumption is you are buying ethanol-gasoline blended fuel of 1:9 mixture--and hopefully not higher.

I much prefer what I see in Wisconsin. Fuel stations there clearly label the pumps and the fuel they are going to deliver with the ethanol content.

I concur with comments that fuel in a fuel system is still in contact with every part of the fuel system when the engine is not running. It is probably worse for the fuel system components to have to sit idle with fuel in them, as the fuel is probably deteriorating.

Based on a completely unscientific study--just reading some comments--replacement of the Fuel System Module (FSM) on c.2007 Mercury engines is something that happens. It probably took Mercury a while to get a component from a vendor that would withstand ethanol-gasoline blended fuels. I hope the replacement FSM you bought was from fresh stock, latest generation, and that Mercury has fixed the problem.

steelhead55
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Re: 90-HP Engine Falls Flat at Full Throttle

Postby steelhead55 » Tue Apr 10, 2018 1:32 pm

I had an [fuel-related problem] problem [caused by] my 225 Johnson-Suzuki four-stroke-power-cycle engine on my Revenge 22.

The low pressure fuel pump had insufficient lift. This was difficult to diagnose.

I could find no specifications for troubleshooting the pump in the repair manual. The manual simply said to check if the pump was moving fuel; it was.

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Re: 90-HP Engine Falls Flat at Full Throttle

Postby jimh » Tue Apr 10, 2018 7:36 pm

STEEL'--so unlike the original engine under discussion, you found the cause of the fuel related problem to be in the engine itself, not in the external fuel system components.

Did you determine the cause of the failure of the low-pressure fuel pump on your Suzuki-Johnson?

How old was the Suzuki-Johnson engine when the low-pressure fuel pump failed?

How many hours of operation on the engine?

Were you using gasoline fuel that was a blend of gasoline and ethanol?

Was there any evidence the pump failure was related to the gasoline fuel having ethanol?

What exactly failed in the pump?

Was the pump mechanically driven?

Was the pump an electrical pump?

steelhead55
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Re: 90-HP Engine Falls Flat at Full Throttle

Postby steelhead55 » Fri Apr 20, 2018 1:47 pm

Hi Jim

Some bad fuel with water contamination had run through the fuel system. The water had collected in the Vapor Separator Tank (VST), and killed the high-pressure fuel pump, which I replaced. I also replaced all the low-pressure and hiqh-pressure filters at this point.

After replacement of the high-pressure fuel pump, the engine would run steadily up to about 3,000-RPM. Any further throttle increase past that would cause the engine to suddenly back down, then pop back up about 15-seconds later. The repair manual I have advised the procedure to check the low pressure fuel pump was to simply disconnect the line feeding the VST and check that fuel was pumping. It passed this test.

At the time the engine was running off a 12-gallon tank on deck;see my thread on the fuel tank replacement project I am still finishing.

After checking the entire fuel system, I could find no restrictions, or anything that could cause vapor lock. I went on-line and bought a new low pressure fuel pump, which was stupid expensive--I think around $700. After replacement, the engine operated normally.

Both the high-pressure fuel pump (which sits in the VST) and low pressure fuel pump (located on the engine, but easily accessible) are electric.

The engine has less than 100-hours and is 2004 Johnson 225, built by Suzuki. Identical to a 2004 Suzuki four-stroke engine.

On a side note, I learned a good, but very expensive lesson. The water in my tank had overwhelmed the fuel-water separator and when I started this process of fixing the engine the separator had only water in it. The sight bowl was all water, so it was not clear that there was water at all in the tank.

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Re: 90-HP Engine Falls Flat at Full Throttle

Postby jimh » Fri Apr 20, 2018 2:45 pm

STEEL'--thanks very much for the detailed follow-up.

Have you determined how the water got into the fuel tank and contaminated the fuel?

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Re: 90-HP Engine Falls Flat at Full Throttle

Postby steelhead55 » Fri Apr 20, 2018 3:08 pm

Yes

See the pic below

https://garys22revenge.shutterfly.com/pictures/114

As you can see, the fuel fill plate on the top of the plastic tank (the one that popped back into shape after being in the sun) has actual holes in it, and and the aluminim had corroded to a terrible state. I am in the process of foaming the tank back in (with water removal capability from the tank cavity) and have replaced the plates with new, very robust ones. I am going to do a detailed post on rehabbing this plastic tank, and my experiences when it is completed.