Seahorse...or anyone familiar with older OMC's

[BBG Marine Electronics]

My recently aquired 86 Ranger with a Johnson GT 150 is still having some misfires. The engine starts and runs perfect up till about 4200 rpm then ocassionally will misfire and cut out. It doesn't do it all the time and only cuts out a higher rpms. Once I ease back on the throttle, smooth as silk.

The owner of the marine service center that I bought the boat from , has rebuilt the carbs, upgraded the VRO pump and fuel pump, replaced both power packs. He says the only thing left to replace is the stator.

Does this sound right ? Originally , I thought it was a fuel blockage problem but we have ruled that out.

Any ideas ?

I knew after the boat sat unused for 18 years there may be some electrical issues but I am hoping the stator replacement will resolve this misfire once and for all.

Brian

[SEAHORSE]

It could be any number of things, but on those older motors, the coil backs were potted with a hard epoxy type compound. This would sometimes "grow and shrink" with temperature changes while running and can cause high speed misfires. They will check fine on a coil tester. Later model coils have a very soft spongelike potting material and the coils are almost bulletproof.

[rudetech1]

I am by no means Seahorse !! I would change all the coils first before hitting it with a stator. For one,it's cheaper, two it's easier. Change the plug wires also. If that doesn't work, then do the stator. Either would cause you a problem, after 18 years, im sur the ignition coils are experiencing electrical breakdown on the higher rpm band. Is this something you or he is paying for? You also have the chance of a timer base going out at higher rpm. The only way he can find this problem is to run the engine and monitor the component in question while it happens. Or he can just keep sticking parts on the engine. This get expensive quick. Any time an engine sits, things go bad by nature. Parts degrade no matter what. Good luck.

[BBG Marine Electronics]

The owner of the service center is paying since the misfire was present when we test drove the boat. At the time, we each thought it might be some bad gas or water in the gas as it only misfired for a brief second when I test drove the boat. He replaced the water seperator filter right after that test drive.

I'm not sure, but he may have already replaced the coils and wires as they look brand new, however this engine only had about 2 years of runtime on it when I bought the boat so its hard to tell whats new and what isn't. At least he is determined to get it running right for me.

On one hand I am happy that all these parts are getting replaced so there will be less to worry about later, but on the other hand , I just want the problem resolved so I can open her up every now and then without worrying about damaging the engine.

Thanks for all your suggestions.....

Brian

[DoferGofer]

Check the two black coils (I think they are called charged coils or something like that) on the stator to see if they are leaking . . . also, check for loose magnets on the flywheel. I have suffered all the pains you are experiencing on my 1985 XP150