1991 Force 35 Compression Test

[Evinrude_NooB]

Hi Everyone.

I'm still having some issues with my 1991 Force 35. I'm going to check compression on the 2-cylinders tonight. What kind of values should I expect from each cylinders?

Thank you in advance.

 

[DAN M VAGOS]

Re: 1991 Force 35 Compression Test

anything above 100psi will run ok but 130+ is great also have the throttle full open and a good charged battery.

 

[Evinrude_NooB]

Re: 1991 Force 35 Compression Test

Thank you, Dan.

I'll give it a whirl tonight and then try again tomorrow. Battery has been sitting for a about a week since last charged.

 

[DAN M VAGOS]

Re: 1991 Force 35 Compression Test

Are you having a problem withit or just curious?

 

[Evinrude_NooB]

Re: 1991 Force 35 Compression Test

Compression came back pretty good: 148 and 145.

I'm having issues with mid through WOT throttle. Also seem to be having issues after it runs for an hour. I'm now trying to systematically see if I can pinpoint any issues. I can sort of rule out low compression.

I check the gas filter, which seems fine.
Cleaned out the carburetor last week.

Are you having a problem withit or just curious?

 

[jerryjerry05]

Re: 1991 Force 35 Compression Test

High speed problems could be??? Water in the gas, a bad pump diaphram or bad check valves.
The fuel system,hoses and inline connectors, replace.
The tank vent closed or the vent hose(built in tank) plugged.
FYI, Comp is great. As long as it's within 5-10 # of each other.
When they say 100#(way low) it runs they need to get another guage.
A good guage will give the right results.

 

[Evinrude_NooB]

Re: 1991 Force 35 Compression Test

Thanks, Jerry.

I already replaced the bad pump diaphragm this season.

Thinking the fuel line is too small, 1/4". I also seem to be getting vapor lock after an hour of running; i.e. Fuel bulb goes flat and gas not getting to carburetor or evaporating there.

 

[jerryjerry05]

Re: 1991 Force 35 Compression Test

My twins run on 1/4in line.Both feed from the tank on 1/4 so the lines not the problem.
Unless the Ethanol has softened the line or there is a pinch point.
Bulb,flat/ That's a venting problem.
Built in tank? The vent line clogged with wasp nests?
The inline connector gone bad?
I removed both of them as soon as I bought my boat.
The diaphram can go bad in 1 second.
A cough,stutter, backfire can rip it.