1990 Johnson 90 hp won't stay at wot

[coin operated]

Recently checked out by mechanic before this problem started. At that time it had good compression between 120 and 128 on all cylinders. Good strong spark. When I went out yesterday, there was water coming from tell tale and exhaust ports. The engine would start perfectly every time, but when you throttle up it would pop out of the hole great, but only stay at wot for 10 to 20 seconds. I pulled the cowling and could hold my hand on both sides of the motor. Warm, but not hot. Any ideas?

 

[racerone]

Test run with another tank and hose.

 

[Silvertip]

Fuel pump time, restriction in the fuel line between the tank and engine, or its carb rebuild time. If the primer bulb is being sucked flat it is a fuel restriction. Continue to run it this way and you will be looking at an engine rebuild as it is obviously running lean. Lean on a two stroke also means lean on oil.

 

[oldboat1]

outside chance it could be a throttle control/cable issue -- or maybe a prop issue, depending on symptoms (e.g., revving but speed drops).

 

[jimmbo]

The engine would start perfectly every time, but when you throttle up it would pop out of the hole great, but only stay at wot for 10 to 20 seconds.

Does the engine die, as in quit, or does it drop to a lower speed and stay there? Is it surging? Is the primer bulb collapsing? Is the fuel tank venting?

 

[coin operated]

It does not die, it just slows way down, like maybe half the rpms. The bulb is not flattened, and pumping it does not change the rpms. It seems like it will run in that state forever at half speed.

 

[coin operated]

And I tried removing the fuel tank cap. No change.

 

[racerone]

Have you tested with another tank and hose ?-----Perhaps hook up a timing light to see if you are loosing spark on one or more cylinders !!----Also do a compression test again and report the numbers.

 

[coin operated]

I haven't got to test on different tank and hose yet. I will have two purchase those. And for the next few days it is way too cold to even mess with! When it warms I will do another compression check and post. Two snow events on the Texas gulf coast in one year! Crazy.

 

[racerone]

Perhaps test run with the cowling off the motor.-----No buddies to borrow a tank from ?---Checked for water in the carburetors ??-----Only with some simple testing / trouble shooting will you find the problems.

 

[Joe Reeves]

You state: "Recently checked out by mechanic before this problem started."... Indicating (sort of) that the engine was running normally but was "Checked Out"... and then this problem arose. Is this the case? If so, possibly the mechanic neglected to secure the throttle cable at the engine?

 

[coin operated]

This gave me an idea. Could a bad shift cable cause these symptoms? I went out and removed the cowling, and I can move the shift lever a long distance without moving the shifter on the remote control box.

 

[coin operated]

The throttle cable is attached

 

[jimmbo]

The initial movement of the control lever would shift the engine, might be around 45 degrees of lever travel before the throttle cable starts to move. Worn cables can cause issues, but I, like others, suspect a fuel starvation problem. Or somewhere after revving up one or two cylinders is losing spark

 

[boobie]

Do a cylinder drop test on it.

 

[oldboat1]

addit. thought on fuel issues -- Do you know if the mechanic used shop fuel or yours? (Yours might be contaminated.)

 

[coin operated]

I appreciate the help. I will work on these and post as I gain more information. Thanks to all of you who make this forum so very useful.