Re: "Newer" 25/35hp OMC compatibilities

[johnyrude200]

It was turning 4800RPM, max, with a test prop. Basically it would hit "max RPM" (for now), hold that for about 8-12 seconds, then lose power. It was pulsating at the top end and acting erratically at anything beyond 2/3rd throttle. I double checked the link and sync and that is all OK. Didn’t get to work on it again yet, but the float was set a bit off, so I’m going to adjust that and then retest. I pulled the high speed jet before typing the last post to insure it was correct, and also clean. The TACH I’m using is a simple one that involves winding a wire around a single plug lead. I will say the motor idles down to a respectable 760RPM before wanting to stall out.

If adjusting the float doesn’t fix the high speed issue (which it seemed fuel starved), then I suspect there may be a clog in the exhaust ports/housing, not allowing the motor to breath the right way. I may try a different fuel pump too, the one I put on there was used but might be undersized/incompatible.

This motor has a story behind it – I went to pull the thermostat cover, only to discover mud dubbers had infested the thermostat cover, clogging up the water outlet at the bottom of the cylinder before it went out the exhaust housing. During the initial run, the motor started to overheat, until a huge glob of gunk/cocoons were ejected out of the exhaust relief ports at the top of the exhaust housing. I pulled the cylinder head completely and cleaned out/used compressed gas on the water outlet at the bottom of the cylinders, but I suspect there may be a lot more crap in there.

Side question – I noticed two holes at the bottom of the exhaust housing on the front side, just above the gearcase. I know the older 20/25’s had water that would gush out of here normally; do these 35’s have that same feature? There was intermittent water spraying out of there, and if there is a big clog below the powerhead/exhaust jacket, then that would certainly provide a major clue as to a clog being the culprit of this issue.

The only other thing I suspect could cause this problem is if the timing is set wrong between the fuel and ignition systems; I switched the mag plate out from a 1979 model which had an alternator; the original did not have this. I haven’t used a timing light on the motor yet, so if all else fails I’ll look at the ignition timing.

Why is it everytime I go to start on a new ‘family’ of motors, the first one always has the most issues 🙂

I remember the first 9.9/15 I tore apart earlier in the year…that ended up being a 20 hour job with all the issues it had, but when I was done, I knew those motors inside and out pretty well!