High RPM Cylinder Cut

[jkjones]

Hey Everyone,
I just inherited an 87 Procraft 1780 Fish and Ski with an 87 Evinrude XP 150. The motor has been sitting for approximately 3 years. We got it started and it runs great. Took it out and will pull my dad slalom skiing just fine. However, at wide open throttle, I am intermittently losing at least 1 cylinder, possibly 2. It is very irregular, but does it constantly. Any ideas on what could be causing it? My dad said it did the same thing before it was stored, so I don?t think it has to do with that. By the way, VRO is still working and engine is completely stock with unknown hours. Appreciate the help in advance.

 

[hidef]

Re: High RPM Cylinder Cut

Could be a coil going bad. They can be tested with a spark tester set at 7/16" look for bright blue spark. When was the last time the carbs were cleaned?

 

[jkjones]

Re: High RPM Cylinder Cut

I don't know when the carbs where cleaned last. I have also tried hitting the choke when it happens, this doe not help ain any way. Would a coil going bad only happen at high RPMs? It pulls out of the hole fine at WOT and does not start acting up until about 4000-4500 RPMs. Thanks.

 

[emdsapmgr]

Re: High RPM Cylinder Cut

Would be interesting to put a timing light on each plugwire when it's missing at 4500. The flashes in the gun will indicate which wire is missing, or has no spark. Pull the cowling off the next time out and have someone drive the boat while you sit in back. Use an inductive timing light-it's an easy test. Weak ignition components tend to fail once the engine heats up to normal operating temps. You've got 6 coils, two power packs, a stator and a timer base-all part of the ignition system. Once you know where the miss is, you can swap coils or power packs for testing purposes.