Re: orifice idle jet 40/50hp motors

[johnyrude200]

On the note of those sync procedures Ive found that just lining up the cam follower with the line on the cam itself and ignoring those sync procedures works OK. I followed those procedures carefully all last season and found none of it mattered in a test tank with a test prop as soon as run on the boat. In other words Id recondition the motor and reset the syncronization following the service manaual, only to have to change everything around once in the tank and on the boat.

What I did find is both with the 40-50 and 70hp motors, all that dwell linkage stuff is just a big headache, but the motors seem to start and run fine up and down the power curve by following the old procedure of lining the cam follower to touch the hash mark on the cam, of course making sure the carb butterflies are closed before that. I mean, even with the 1989-thru motors, the hash mark is still on the cam yet the sync procedures basically ignore this. Why leave it there? Reuse of old parts?

When I set them up following that long procedure they wont start right, have big back pressure issues, and run erratically both in the tank and on the boat.

I question whether that procedure loses it relevance with an older motor? The reason I mention this is having gotten my hands on a few older motors from different years and horsepowers, and seeing the difference between a low hour motor, a middle hour motor, and a well used motor definitely makes a big impact on overall running, starting, and to a certain extent power characteristics. The high hour motors I refer to arent knocking and clanging away, and still show reasonable compression numbers. But a low hour motor with high compression certainly runs and performs much better.

Reconditioning a variety of motors it seems like a better condition one is much more forgiving in general and tolerant to settings perhaps being ‘off’ without really showing any significant difference in performance. In other words, they seem less sensitive in general.