Evinrude 90 HP Idling issues Help Please

[waterman5555]

Hi, I have a 89 or 90 evinrude 90 hp 2 stroke V four outboard it starts up at three quarter throttle on warm or cold starts and runs to top speed great BUT when in very low almost idle speed or when switched from forward to reverse gears it stalls out it does seem to do it less when the engine is cold and I should also mention the engine shakes alot on low speeds now I have changed plugs and wires so far next step is compression I think I was told today that if I raised the idle it may do the trick it doesnt have an rpm guage but it does sound pretty low before stalling out any help would be greatly appreciated
Thank you in advance .

 

[Daviet]

Re: Evinrude 90 HP Idling issues Help Please

Check the compression, will the spark jump a 7/16" air gap and is it bright blue? When was the last time the carbs were overhauled?

 

[archcycle]

Re: Evinrude 90 HP Idling issues Help Please

While you may very well be at very low RPMs at idle, the most likely causes are no spark to one or more cylinders, no fuel to one or more cylinders, or low compression on one or more cylinders.

You really won't know anything about the RPMs until you buy a tach. For example, how do you know it runs to top speed great? Without a tach you really have no way of knowing whether you are even at top speed. These motors want to run 5500 +/- 300rpms. You really need to know if you're at something like 4500 or 6500.

Then there's the idle adjustment. That's set via a timing adjustment, and is based on a precise RPM while in gear in the water.

And on the hose- you said you have to give it 3/4 throttle to get it to start. It's very easy to ruin a motor by revving it too high on the hose. A tach will help you not do that.

It's one of the most important troubleshooting tools you can have.

Like Daviet said, check spark and compression, and put some pre-mixed oil/gas in a spray can and try spraying some down the throats of individual carbs while it's trying to idle. That can help you pinpoint a fuel restriction in the carbs.

Those are the 3 basic things to start with.

 

[waterman5555]

Re: Evinrude 90 HP Idling issues Help Please

I will go and get a tach and follow your recomendations thank you very much for the replies I am new to this forum and outboard repair my backround is in truck repair and towing I will update you all as soon as i have some info again I thank you .

 

[emdsapmgr]

Re: Evinrude 90 HP Idling issues Help Please

A low idle can cause the engine to shut down when shifting into forward or reverse gear. That engine should idle between 650 and 750 rpm-set when the boat is floating normally in the lake and is in forward gear. As was mentioned, it's hard to properly set the idle without a tach.