Powerhead and electronics swap, motor not running right. 200 hp

Johnnyl30y

Recruit
Joined
Jul 24, 2026
Messages
1
Backstory....i am a harley davidson mechanic and do a lot of tinkering on boats on the side. I recently traded for a boat with a blown motor. The guy bought and included a complete used powerhead that a boat shop told him would be compatible. The motor is a 1995 johnson 200 venom. The parts powerhead that was included on the deal was missing the stator, timer base, starter motor, and some other things. I stripped the wiring harness off of it, took the carbs off and cleaned them, and then took everything off the original motor down to the mid section. Used the donor block, intake, and carbs (the carbs are noticeably different), along with the original 1995 wiring harness and ignition components.

Got everything assembled, tried to fire it up in test tank and couldnt get it to stay running. It would idle roughly for 5-10 seconds, then due. I kept playing with the idle mixture screws, then the idle timing, didn't seem to matter what I did couldn't get it to idle smoothly or consistently at all. Couldn't get it to rev up at all. Took a known good fuel tank and line off my other boat and was able to get idling a little better but only by cheating and having the throttle plates open a tiny bit. still not good but could Rev it up in the test tank. Took boat on river, would stay idling, but not smoothly at all. As soon as i took off It couldnt get on plane was bogging out and the warning buzzer would go off until I throttled down to idle then immediately shut off. Motor wasnt hot to the touch, but I did remove the thermostats to make sure. This process has repeated over and over.

I have checked compression.... 98-105 all six cylinders. Spark... seems to not be super consistent, all cylinders have spark, only a couple were arcing across 7/16" and not every time. Timing seems very hard to get adjusted. I'm questioning if all components are compatible with each other or not. Please help.
 
Top