90 hp Johnson

3/21/16 @ 7:52 PM
ORIGINAL POST
godevil
godevil
USER since 2/7/12
I'm having trouble with the motor at high speeds it starts to cut out if I lower the rpms it smooths out and runs fine any ideas on what the problem may be? Thanks in advance.
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Displaying 1 to 9 of 9 Posts
3/23/16 @ 11:41 AM
GoldenRules
GoldenRules
USER since 10/29/13
It is either a fuel or spark problem. You know you have fuel and spark because the engine runs. The question is which one of them is not at the appropriate levels at the full throttle position.

First I would try cleaning the carb. It sounds like you may have a main jet that is plugged. The main jet meters your fuel from the 1/2 to full throttle position. That is a cheap and easy fix.

If that doesn't work I would check your fuel pump or ignition(spark) system. You may have a fuel pump or powerpacks that are starting to fail.

Just my 2 cents, I am not a mechanic put have experienced these problems on my sleds and outboards and these were the fix.

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3/23/16 @ 8:59 AM
lakeshiner
lakeshiner
USER since 7/20/09
Sounds like an old motor of mine that sat unused for a while and the carb got gunked up. It would start and go a little, but full throttle would kill it.

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3/22/16 @ 5:43 PM
BugleTrout
BugleTrout
USER since 9/27/01
I had a similar issue with an older Mercury. Ended up being the screen in the carb. It got gunked up with particles/sludge over the years and needed to be flushed out. Of course it decided to act up 7 miles out of Kewaunee but it got me home. Just took a long time at 1/4 throttle.

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3/22/16 @ 5:37 PM
Plmlk
Plmlk
MEMBER since 12/18/07
Tonto, if he has spark at low / medium RPM why do you suspect it is a spark issue at high RPM?

Also agree with Wally - could be the hose / primer bulb. Years ago I had a 150 HP Evinrude Intruder. It performed well at low RPM, but started choking at high RPM. As it turns the check valve in the primer bulb let loose and lodged itself on the leaving side of fuel line which restricted the diameter. At low RPMs it performed fine, but at high RPMs it was starved for fuel.

I'm a boating junkie and enjoy wrenching on my own sleds and outboards. Over the years I've had plenty of outboard issues and all but one was fuel related. Fuel delivery issues easily account for 80% of outboard issues.

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3/22/16 @ 9:33 AM
Tonto-B
Tonto-B
USER since 9/7/05
Sounds like it could be spark.

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3/22/16 @ 9:30 AM
wallybeav
wallybeav
USER since 11/6/08
also replace your hose from tank to motor. I had same exact problem and it was the bulb and slight crack in hose.

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3/21/16 @ 9:31 PM
ayeFeesh
ayeFeesh
USER since 5/17/11
Sounds like fuel issue to me as well.

Did it just start doing this recently? If so maybe bad fuel from last year.

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3/21/16 @ 7:58 PM
Plmlk
Plmlk
MEMBER since 12/18/07
Never say never, and never say always, but if you have spark - you have spark, no need to look any further.

And if you have spark, its time to move onto fuel delivery. Have you checked your fuel filter, cleaned your carb???? 9 times out of 10, older outboard problems are always fuel related.

What year is your motor? Fuel injected or carburetor?

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