Runnin rough @ times

[AlpineMike44]

Hey guys, great site, btw.<br /><br />I've got a Johnson 35hp Sea Horse '82-'84. For the most part it seems to run well, altho the previous owner said he got 30Mph out of it on the same boat, I'm getting 35Kph....quite a bit slower.<br /><br />The speed issue is not as important as what's happening intermittently: motor runs fine during idle, then full throttle... stop and fish for 20mins, starts fine, idles fine, then when throttling up, it coughes and misses and runs very rough...like it's running on one cylinder. Rev it, turn it off, play around with sparkplug wires, start it, and it may or may not run fine again. After it is running ok for the most part after running rough, it is smoking like crazy out of the exhaust.<br /><br />I'm running a mixture of 50:1 and the carb was cleaned by the previous owner (who is a friend) and I've put new plugs in it.<br /><br />It only seems to run rough after sitting for awhile, the trouble hasnt appeared while already running full throttle. That is to say it only occurs promptly after startup after sitting off for a period of time, then attempting to run full throttle.<br /><br />Thanks<br /><br />Mike

 

[DJ]

Re: Runnin rough @ times

Mike,<br /><br />You are probably having a coil break down after a hot soak.<br /><br />Do you have an inductive timing light?

 

[AlpineMike44]

Re: Runnin rough @ times

DJ,<br /><br />I should have access to an inductive timing light, yes.

 

[DJ]

Re: Runnin rough @ times

Mike,<br /><br />Hook the inductive light up to one plug wire at a time. When the engine acts up, see if either plug is NOT firing.

 

[AlpineMike44]

Re: Runnin rough @ times

Thanks for the tip DJ, appreciate it.<br /><br />Pardon my ignorance as I'm far from a mechanic, but by "....having a coil break down after a hot soak." Do you mean the coil in the spakplug wire itself? Cuz that would be a nice easy fix to just replace it, I'd think..?<br /><br />Thanks again

 

[DJ]

Re: Runnin rough @ times

Mike,<br /><br />No, the coil that fires the plug. Follow the plug wire(s) back from the plug. That/those are the coils.<br /><br />Check any connections at the coils. Also make sure their mounting screws are tight.