cylinders not firing 225 johnson

I installed a 1991 225 johnson powerhead on my 1996 225. Not knowing about a wiring harness adapter, I put all my electronics on the 1991, everything except the carburators. My engine runs but the firing sequence seems to be off. One half of the cylinders are running cold. I'm guessing timing, as disconnecting the shift control sensor makes no improvement.

Re: cylinders not firing 225 johnson

have you verified spark on all six? a cold running bank could be a bad t-stat.<br /> the stator charge coils could also be suspect as one feeds one bank and the other one feeds another bank.<br /> first step is to verify spark on all six, next step will be to make a TDC index mark and check ign timing on #2 cyl as well as #1.<br /> normally,as the trigger is arranged with equally spaced coils if #1 is correct the rest have no choice in the matter. <br /> timing on that motor is a matter of physical spacing of the trigger coils and their relationship to the trigger magnet on the flywheel hub. if one trigger is in the correct position the other 5 have no choice.<br /> it is possible to have the trigger magnet slip but you will still have spark on all six it just wont be at the correct time and either you get a lot of backfires or it does nothing.<br /> you may also have shaft spline sealing issues as the design of the drive shaft and crankshft changed from 91 to 96. <br /> Dhadley remembers more about it than I do, but I also know that a few also cause clearence issues that will lead to lower crank bearing failures.<br /> also check the spacing on the outer flywheel magnets.

Re: cylinders not firing 225 johnson

thanks for the input. there is spark on all six. the engine runs but will not rev any higher than 4000 rpm under way. with no load it revs just fine. since this powerhead change i have not rechecked the timing due to lack of testing tools. could improper timing create this type of problem? Since my 1996 ran fine before a thrown rod, I'm assuming that all the electronic components that I've changed are working properly.

Re: cylinders not firing 225 johnson

it could but ill clue ya into a secret, reving to the limit with no load can wipe roller bearings and running with excessive retard or advance can lead to piston failure.<br /> my advice is buy the correct tools or take it to a professional and let them test it. could be a carb issue which is most likly what took out the last motor.<br /> its time for some careful testing prior to attempting to run WOT at full load.<br />and do not attepmt a high speed run with the airbox off.