1987 Force 125 runs very slow until engine warms

Hello All,

I have a Force 125 on a 21' sportfish 2000 boat. The engine will only run about 8 mph until the engine is completely warm......usually about 15 minutes or so. during that time, it feels like it is running on 2 cylinders and the plugs are wet.

to try and isolate the problem, I put in some hotter plugs.......nope, didn't do anything except cause pre-ignition after it warmed up.

after 15 minutes, the engine jerks for a minute, then "takes off" and runs perfectly the rest of the day. you can turn it off, fish, or troll, or whatever, and it runs perfectly. but the next day, it will be exactly the same as before.....running slow and poorly for 15 minutes, then runs perfectly.

the coils were all replaced, and the fuel pump was rebuilt. I rebuilt the carbs. I put in new floats. I replaced all the fuel lines and of course the correct surface gap spark plugs. The compression is about 135 in all 4 cylinders. I am running 87 octane gas.......

I get the feeling I have something adjusted wrong in the carburetors.........like it is flooding badly when cold........but I cannot figure out where the heck I am going wrong with the adjustment.

Thanks in advance for any suggestions.....

Re: 1987 Force 125 runs very slow until engine warms

did you set the fuel mixtures screws to one turn out from lightly seated ? If you do it you will want need to re-adjust your idle as it will change rpm. But it doesn't sound like that would be it. I'm sure someone will chime in that is more knowledgeable than me.

Re: 1987 Force 125 runs very slow until engine warms

Just be patient and let it warm up. Do you wake up directly into a marathon?

Re: 1987 Force 125 runs very slow until engine warms

15 min is not right. You should be able to go as soon as you start.
Could be either the electrical or the fuel. Will give you a few of both to check.
When cold, try to pull off a plug wire and see if it stalls? Do #1 and then #4
If it stalls when you pull a certain wire? Then switch packs around and see if it follows the pack.
Possible the packs not kicking in until it gets hot? Maybe a coil doing the same.
Check all the wire connectors,tighten them. Check the grounds.
The wire connections,they can go bad under the shrink wrap.
I replace them on every motor I work on.

Usually when the floats are replaced the old stuff wasn't bad.
The original was/is the best. You have trouble before the change?
Could be the floats not set right.You have the manual?
Any fuel comming back through the carbs?
Do the linc and sinc from FrankA Top post in the Force Forum.

Re: 1987 Force 125 runs very slow until engine warms

Electrical or fuel? With a simple timing light you can check if it is electrical by observing the strobe while testing each plug wire. A missing strobe means electrical problem. If no missing strobe, obviously it is fuel related. While not "loading up" when cold, stop and check all plugs to find out which one is bone dry. That will be the problem cylinder(s). Personally, I believe it is electrical. Let us know.

Re: 1987 Force 125 runs very slow until engine warms

Finally, problem solved. It was electrical........the trigger was bad. Thanks for your help, took me awhile to figure it out

Re: 1987 Force 125 runs very slow until engine warms

Did someone explain to you how a 15 minute warmup changed the trigger function. Curious mind wants to know.