90hp force won't run past 4000rpm

zarrman · Jun 3, 2010

1992 force 90hp starts good, idles good, revs up good. but under load when wide open won't run up past 4000rpm but back throttle down to 3500rpm runs good. compression is 122 to 130 on all three cylinders. anyone have any idea what could be wrong with this motor. thanks

pnwboat · Jun 3, 2010

Re: 90hp force won't run past 4000rpm

There may not be anything wrong with it. What type of boat is it on? What length, weight etc. Also what pitch prop are you running? A prop with too much pitch will prevent the motor from turning optimal RPM's.

Also check to see if the butterflys in the carburetors are opening all the way. They should be perfectly horizontal when the throttle is opened up all the way.

zarrman · Jun 3, 2010

Re: 90hp force won't run past 4000rpm

yes i have had this boat for five years now and this just started out of the blue the other day on the way back to the dock but it normally ran 5200rpm but now it seems fuel starved at 4000 or it misses at 4000 but will run flawlessly at 3500rpm to idle

jerryjerry05 · Jun 4, 2010

Re: 90hp force won't run past 4000rpm

Do a spark test.Then check the vent line and the gas line for blockages.Change the squeezie.Check the filters.
Ethanol is messing up a lot of motors.It's delaminating the inside of older hoses causing clogs in the carbs and fuel filter.Check for soft hoses and junk in the filter on the motor.Check the diaphram. J

zarrman · Jun 4, 2010

Re: 90hp force won't run past 4000rpm

everything seems to check out just replaced the bulb cause that was what i thought the problem was initally. by diaphragm do you mean fuel pump

zarrman · Jun 4, 2010

Re: 90hp force won't run past 4000rpm

there is spark on all three cylinders also. could it be a bad gasket on the intake side of the motor. maybe causeing it to suck air

pnwboat · Jun 4, 2010

Re: 90hp force won't run past 4000rpm

Yes a an intake leak can cause it to run lean. Make sure all the bolts that hold the carburetor adapter to the block are tight. With it idling, you can take some carburetor cleaner and spray around the base of the carbs and carburetor adapter. If the motor changes idle speed, you may have found a leak. Be careful not to spray directly into the openings of the carburetors. The cleaner has a tendency to wash away the lubricating oil that is mixed in with the gas from the engine bearings. Same thing applies to starting fluid.

Make sure the vent for the gas tank is open and not plugged. You can test by opening the gas cap just enough to allow air into the gas tank.

maxum_man · Jun 4, 2010

Re: 90hp force won't run past 4000rpm

Hey!! I had the same problem with my 1992 120 hp l drive motor. I found a cylinder drain cover was cracked. I have ordered 2 good used ones, so I will liet you kow if that helps any. I figured that there was a leak in the recirc. system, so maybe thats what was causing it.

You might check to see if you have a recirculation system like I do and make sure the tiny hoses arent clogged up too!

zarrman · Jun 4, 2010

Re: 90hp force won't run past 4000rpm

i'll check it out. let me know if that fix's your problem

maxum_man · Jun 4, 2010

Re: 90hp force won't run past 4000rpm

mine wont get any attention for a week or two (Too many duck and goose calls to make!!), but I will repost with results! I am also replacing my entire ignition system just to have a fresh start!

zarrman · Jun 6, 2010

Re: 90hp force won't run past 4000rpm

well i checked and tightened everything on the intake side and still no help

90hp force won't run past 4000rpm

Cadet

Rear Admiral

Cadet

Supreme Mariner

Cadet

Cadet

Rear Admiral

Petty Officer 2nd Class

Cadet

Petty Officer 2nd Class

Cadet