force 1988 125 missing, sluggish

[Den68]

Hi I have a force 1988 125hp that I took out last weekend and it seem to run ok at first with a bit of a shake or miss, as I ran it up to speed it was fine, after a minute it bogged down and seemed to be running on three cyl with the fourth kicking in every so often. I brought it home did a compression check and got 136, 140, 145, 144 also did a check on spark, all coils firing well, and checked flywheel key. Motor has new impellor and new head gasket. Going to do a static timing check today, but I really wont know whats going on until I try it under load again, looking at putting new reeds in as well, carbs seem clean and operating well. Just wondering if anyone has any other ideas or if im headed in the right direction. Thanks

 

[SkiDad]

my boat did a similar thing when I first got it (only at idle) - the previous owner had the fuel mixture all messed up. he had the top on 3/4 turns out and the bottom 5/8 turn out. I set them both to 1 turn out and adjusted my idle up to 1100 in neutral / 750 in gear and it cleared that all up.

 

[Jiggz]

Compression numbers seems to be within range. And the fact you have spark on all plugs tells me it could be either fuel related, carburetion or reed problem. If you haven't install the clear fuel filter mod between the fuel pump and carb inlet, now is the time to do so. If the clear fuel filter stays at least 3/4 full when running then you know it is not a fuel delivery problem. The next step is to find out which cylinder is not firing or misfiring by quickly pulling and replacing the plug wire and listening for change in engine tone. After identifying the not firing /misfiring cylinder the next step is to check the reeds. Although, I might say 125's in the 85's~89's seldom have reed problem just like the late 120's. If for some reasons the misfiring seems to be local between two adjacent cylinders fed by the same carb, then you know the problem is carburetion.

 

[Den68]

Thank you for your info, I checked and set the timing today and with great difficulty. The motor runs and idles well but that can change under load, I will set up the carb mixture screws and am waiting for the carb kits. I will take it out on the water again this weekend and try it again. Thankyou

 

[jerryjerry05]

Most time you don't need to rebuild the carbs.
Just a good cleaning will work.
Is it spitting back through the carbs while it runs?Yes, the reeds need inspection. No, then look somewhere else.
Running bad at high speed has nothing to do with the low speed jet.
A piece of dirt in a high speed? Maybe.Drop the bottom carbs bowl and see if there is crud in there.

The comp test. Did you remove all the plugs when you did the test? Or just one at a time?
The readings should all be real close. If mine had any more than 5 pounds difference I'd start looking for a reason?
Even a good comp reading doesn't mean everything is good.
I had a miss in one motor. Did a comp test and it was 145# all 3 cyl.
The middle cylinder the head gasket gave out and was letting water in.

Check the fuel line vent hose for a clog or pinched hose.