90hp Force Mystery

[Diston]

Hi

I have a 1990 90HP Force and last time out started experiencing motor problems. The engine bogged down when I throttled up, and will only push my boat at 5knots.

I put new gas, new plugs, and a new filter in it. I run the motor at 50:1 using 89 octane gas with octane boost in it. I also put methal hydrate in my tank for water. And it still runs the same.

Here are my observations: 1. Will not rev up under load 2. Rev's up in neutral but is rough, 3. Gets very hot, 4. smells like unburned fuel, 5. cold crank compression is 125, 125, 125, 6. stalls when you put it in gear in the water.

HELP PLEASE...

 

[steelespike]

Re: 90hp Force Mystery

Classic symtoms.poor fuel delivery does squeezing the primer bulb help?
Could be a dirty carb(s).If choke helps then most likely dirty carb.Could be missing on one or more cylinders.You need to check for spark.Be careful how you do this as you can damage the ignition if you trouble shoot improperly.

 

[roscoe]

Re: 90hp Force Mystery

hot, no power, stalls when put in gear, all points to a lean condition.
Raw fuel smell is likely gas leaking out of the carbs or hoses, where the gaskets have dissolved from the methanol.

Stay away from the methanol. See the warning in your owners manual.
This may be what messed up our fuel system.
It is a strong solvent that will clean the gunk out of your tank, and send it into your engine.
It also wreaks havoc in your fuel system, dissolving gaskets, rubber, and fuel pump parts, that weren't designed to withstand it.

There is enough ethanol in the gas we buy nowadays.
If you have a serious water-in-fuel problem, then get a fuel/water separating filter.

The problem now is that your entire fuel system needs to be cleaned.
Carbs disassembled and rebuilt, filters replaced, recirculation system cleaned out, fuel line cleaned or replaced, gas tank pick-up cleaned.

For your reading pleasure:

"If you add too much Meoh (Methyl Hydrate, Methanol ) to too little gas bad things can happen. Rubber parts and gaskets in your carb may start breaking down or you may burn a hole in a piston from an overly lean mixture. I had to run my old Chevy truck home one day on MEOH. Half way home it started running real bad. By the time I got to my driveway it would run no more. I coasten into the driveway got out and went inside to bed. Later when I got up, I went out to look at my truck to find gas/rubber residue all over the top of my manifold where it had run out from what used to be gaskets in my carb. "

 

[Bigprairie1]

Re: 90hp Force Mystery

Definitely sounds like a fuel delivery problem, no question.
'Do' the fuel system. Filter, lines....how old is the fuel?
Then move to the Carbs. I'm just starting to learn about my force 90...but this is something I'll be brushing up on.
Good luck....remember everything can be fixed.

 

[12Footer]

Re: 90hp Force Mystery

Both good places to start, Diston. Another I can think of is one dead cylinder. Classic symptoms (runs and revs seemingly great without load, but bogs down under load).
To find out which cylinder, touch the head by each plug -- BUT NOT TOO CLOSE . If you find one cooler than the other two, that confirms a dead cylinder, and points to the particular culprit cylinder.
Of course, you'll then have to find out what component of internal cumbution is missing (fuel,fire,respiration).

Also, you show four compression results, but the 90HP is a 3cyl. I am assuming the "6" was a typo.