Misfire at WOT on 115hp Johnson V4, powerpack??

[BrianDeg]

SO I had the boat (1995 four winns jet boat) out yesterday and it ran great after cleaning carbs for about 15 mins of WOT, then it started to develop a misfire. I tried the primer solenoid to see if it was a fuel issue but that only made it worse, when I backed off the throttle a little it would run better. We stopped and checked the plugs which looked okay. Went back out and it ran fins again for 15mins and then it started to misfire but this time it was much worse and eventually led to it stalling and wouldnt restart. Once back on land it did start about 45 mins later.

I think it may be power pack, your thoughts? How do I diagnose?

 

[jones56]

Re: Misfire at WOT on 115hp Johnson V4, powerpack??

Did you find the problem? My engine is doing the same

 

[emdsapmgr]

Re: Misfire at WOT on 115hp Johnson V4, powerpack??

You will find some excellent ignition troubleshooting for this engine at cdielectronics.com. The fact that the engine bogged when choked indicates it was not running lean. Weak electrical components tend to fail when the engine heats up to normal operating temps. Once the engine starts to miss. you can easily check for spark with an inductive timing light on each plugwire.