89 50hp force misfire 2 ~ 2500rpm

[89max]

Hello Boaters, I need your help with 89 50hp force with misfire around 2500rpm (I don't have a tachometer). The timing light would rapidly flashing as rpm goes up but when reached about 2500rpm then the flashing would skipping out and engine starts to sputter and smokes. When switch the timing light to #2 cylinder it would does the samething. Disconnected the timing advancing arm and manually pulled up, you can see the engine is reving up but when reached around 2500rpm then the flashing would skip again. What other tests can I check? The cd module has date code of 2005 and still looks pretty new. Compression in both cylinders over 100psi. Rebuilt carburator and cleaned out the fuel system. Thank you for your help.

 

[further]

Re: 89 50hp force misfire 2 ~ 2500rpm

Out of curiosity, what spark plugs are you using? Did you set your carbs right after the rebuild? Could be you're running too lean which is dangerous and could damage the motor. Also compression should be between 130 - 150 for that motor, but more importantly should be no more than 15 psi difference between the two. If you don't have a manual yet, buy a Clymer Manual - has all kinds of troubleshooting and testing info.
Good luck

 

[89max]

Re: 89 50hp force misfire 2 ~ 2500rpm

The sparkplug is Champion L78V. I removed the flywheel lastnight found nothing wrong, all the magnets are in place and very clean. Checked all the wiring for for cut for loose and found nothing. I cleaned the carb adjusted engine speed for smoothness and set it best running at idle. Clean the wire mesh in the filter mounting on the engine also cleaned out the fuel tank as best I could. Took the boat out last weekend and it could not get up on plane and only during about 10 or so mph at wot. I squeezed the primer bulb but made no different. Water is coming out from the two exhaust holes so the engine is not overheated. SHould the timing light stay flashing rapidly with the engine speed reving up and stay the flashing at the same speed with the engine? Thank you.

 

[further]

Re: 89 50hp force misfire 2 ~ 2500rpm

You should get a clymer manual. There are specific procedures to follow so that the engine is synchronized - called lync and sync as well as carb adjustments (throttles open up all the way and choke closes all the way, etc.)that should not be done without following a manual. Clymers also recommends Champion UL18V surface gap plugs so does the following site - http://www.sparkplugs.com/results_appOther.asp?otherMotiveID=12351&mfid=2
This maybe you're problem - change out the plugs for these surface gap plugs and see if that helps.

 

[89max]

Re: 89 50hp force misfire 2 ~ 2500rpm

Thank you for your suggestion and I will replace the plugs with Champion UL18V. Also, does this engine has reving limiter built in?

 

[F.O.R.C.E.]

Re: 89 50hp force misfire 2 ~ 2500rpm

Hi
Just a quick question.
Dose the miss sound like rocks going through the motor when you raise the throttle?

 

[89max]

Re: 89 50hp force misfire 2 ~ 2500rpm

No, it not knocking. It sputtering out and no power. I checked the timing at idle and it was about 10?BTDC, tried to bring it down to 0 but it will not idle well so now it's at 4-6?BTDC. When it starting to sputtering the timing light also skipping out, so I was wondering if this engine has the reving limiter. Thank you.

 

[pnwboat]

Re: 89 50hp force misfire 2 ~ 2500rpm

This motor does not have a rev limiter. Kind of sounds like you're losing spark at higher RPM's. I would think that the timing light should flash in sync with the ignition pulses each time it fires the coil. The fact that the timing light flashes are not consistent when the engine starts to sputter, may indicate that the ignition spark is faltering. Is it hard to start?

Make sure you check that all of your grounds are making good contact. Especially the ground wire that goes from the CD unit to the coil mounting bracket, the grounds from the coils to the bracket and I believe there is a wire that grounds the bracket to the block.

 

[89max]

Re: 89 50hp force misfire 2 ~ 2500rpm

It is very easy to start. I will check those ground wires and re-tight them again. By the way I pulled off the flywheel but now don't know what is the nut tighten torque should be? Thank you.

 

[fishin1789]

Re: 89 50hp force misfire 2 ~ 2500rpm

The Clymer manual says on page 383 that the flywheel torque spec on a 40 & 50 hp prior to 1995 is 80 ft/lbs. (108.5 N.m)

hope that helps!

 

[89max]

Re: 89 50hp force misfire 2 ~ 2500rpm

Thank you for the flywheel torque spec.

 

[89max]

Re: 89 50hp force misfire 2 ~ 2500rpm

Had it into the lake last weekend and it's running top notch condition 30mph!! Thank you all for your advices. I think it had something to do with the grounding wires and the sparkplugs. Now I can take the kids out for fishing. Thank you all again!!

 

[pnwboat]

Re: 89 50hp force misfire 2 ~ 2500rpm

Great! Good to hear that it was a simple fix.