Re: 1990 225 evirude
Well, I'd read somewhere to remove the timing cam roller so that you can manually advance the timing to the stop with the engine running (in neutral) while leaving the throttles closed, and to set it to 2 degrees less than what's called for. So I set mine to 16 degrees like that.
HOWEVER, at the moment I'm borrowing a test prop while I'm chasing other engine problems, so I was able to run the engine to the specified rpms in gear in a tank and check timing - still 16 degrees. I readjusted it to 18 degrees as per the manual, and out of curiosity retested it by advancing the timer base to the stop with the carb butterflies closed - it was 18 degrees by this method as well. Now, with all of that said, if I didn't have access to a test prop and was just setting it by advancing the timing with the butterflies closed, I'd probably err on the cautious side and leave it 1 or 2 degrees less than specified.