1995 Force 120 Hp OB idle issue

[pnwboat]

Yes it looks like you may have an issue with #2 cylinder. I would take a peak at the top of the piston through the spark plug hole and see if it looks any different than the others. Pay particular attention to the top edge of the piston. If it looks like there's a dent, or a piece missing, then I would suspect a ring has broken. If that doesn't work, you might want to think about removing the head and checking the head gasket, and cylinder walls for any issues.

Of course the other option is do nothing at all. I've seen several motors where the owners have around 90LBS in one of the cylinders and the motor seems to run just fine. Probably not running at peak performance, but it starts and does what they need it to do reasonably well.

 

[SkiDad]

just a note when setting the timing on a force 120 with mercury ignition you need to set it to 32 static (cranking) which will be 30 while running. It's the opposite of the older ones where you set it 28 to get 30.

 

[EugeneP]

Thank you so much for your advices!..Following the steps described above i was able to set the timing at 32d, static.
After this I took the boat to the water.and the engine, would run fairly strange..it would slightly accelerate itself, make a noise..like knocking and then it would just die. I made some videos at this point (at no point during the videos I touched the acceleration or screws):

video 1: ht[FONT=&quot]https://youtu.be/ZxVuKTyhz2Q[/FONT]

after some adjustments (mostly idle speed): https://youtu.be/rxbZD9iMIL8

I read again again and followed to the letter Frank Acampora Synchronizing carb guide and I managed to properly set it up: Idle in neutral around 900, and in gear 750. It would idle nicely, not die..no odd noises, video is here: https://youtu.be/_rCk5Snuy0o

Then, i took it for a ride..reached abt 30mph at 5000 rpm (lots of wind and waves): https://youtu.be/XizdBvojmNM

When i got back to the dock..i wanted to test it again, big surprise: idle was again at 600, and even tough the engine was warm it would not start without cold start procedures (click middle button and accelerate almost fully) and even then took 2-3 attempts. I checked the idle speed lock nut (tower shaft) and it was well tighten. So, it seems it would not keep the adjustments i did...can it be because of the low cyl 2 compression? i cleaned the carbs abt a month ago, and there was the same issue. Trough the movies, you can also see that sometimes, without touching the controls or any screw..it would just accelerate itself. I think its important to mention that after adjusting timing and carbs, i didn't adjust the throttle cable,..the engine starts accelerating only when the lever is at 45 degrees..and reached WOT almost when fully pressed. Not sure if this has anything to do with the issue.

What could be the culprit?..why it would not keep the idle adjustments and after running it would revert back to 600 rpm and hard start? any other ideas?

 

[SkiDad]

My boat runs really well but the idle speed sometimes varies between starts. Sometimes it'll start in neutral at 800 RPM and sometimes at 1100 RPM but eventually it will even out to about 1000 RPM out of gear or about 750 in gear I've fought it to find a happy medium. I think it would be best if you set your idle to be about 800 RPM in gear - that is still within spec. That might be a sweet spot for you. Your wot run sounds normal in the video. idle has a lot to do with it starting right. Also have you tried starting it in fast idle ?

 

[EugeneP]

My boat runs really well but the idle speed sometimes varies between starts. Sometimes it'll start in neutral at 800 RPM and sometimes at 1100 RPM but eventually it will even out to about 1000 RPM out of gear or about 750 in gear I've fought it to find a happy medium. I think it would be best if you set your idle to be about 800 RPM in gear - that is still within spec. That might be a sweet spot for you. Your wot run sounds normal in the video. idle has a lot to do with it starting right. Also have you tried starting it in fast idle ?

By fast idle you mean, pushing the middle button.. accelerate and crank the key? or just increase idle to abt 1000 rpm?

 

[jerryjerry05]

Yes fast idle is the handle pushed forward. That can boost the rpms as much as 500+
That position is good for starting.
The idle in N should be about 1050-1150.
In gear 750-800

My fast idle on 1 engine gets about 800-900 more and the other only gets 300.
The link and sinc will help get more if you need more.
Mine start fine so I don't mess with them.
Also I never hardly ever get past 5000rpm's.