Running Issues

[Capt Cornnuts]

I have a 1975 25hp that starts fine and runs great at wide open throttle and idle but only when its not in gear. Its a little rough in gear at the lowest speed but at 1/4 throttle it cuts out and snaps back to life over and over again. I have had the carb rebuilt, replaced both coils, and have a new fuel pump and filter. I run 50:1 and have tried leaning it out a little but it still seems to foul plugs about every 5th or 6th trip and dosent have any effect on the cutting out issue. I have considered sinking the boat if it continues. Any suggestions would be helpful.

 

[bktheking]

Re: Running Issues

At idle and revved out of gear most motors will not exhibit issues the same as they are under load. Get yourself a big barrel, run the motor in it in the dark and look for sparkplug wire/boot leaks, it sounds like an ignition problem. Bucking under load is indicative of ignition cutting in and out.

 

[Daviet]

Re: Running Issues

Have you checked the compression? Pulled the flywheel and checked coils for cracks, points for clean and proper gap?

 

[Capt Cornnuts]

Re: Running Issues

Thanks for the replys so far. I almost only use the boat for catfishing at night and actually have checked for any signs of mis-fires. At this point I am fairly sure I havent got any kind of coil or wire type issues since everything is new, Altho I am not ruling anything out at this point. The compression seems to be ok since both cylinders are the same but im not really sure what the compression should be. As for the points...what should the gap be? I was also told it may be a timing issue since it happens only under a load but im not sure as to how to advance or retard the timing.

 

[bktheking]

Re: Running Issues

I don't know if there is a timing adjustment, usually the flywheel key sets the timing. The point gap is .020 and if they have the slightest amount of dirt on them they will misfire.