With the new stringers in place and the motor back in I started work on the next phase of the restore. One thing I wanted to do though was run the motor in the driveway (on ear muffs) at least once a week. Basically to keep the new batteries charged and also to check how the motor runs before taking the boat out for the first time. Also with the motor running I could troubleshoot the problem with the gauges - none of them worked! However, each time I let the motor run for around ten minutes it would overheat. The temperature gauge didn't work but I could tell that there was a problem from the gurgling noises and the steam coming out of a small hairline crack in one of the exhaust manifolds. (the crack was barely visible) As it got to this point I would shut the motor down immediately and turn the water off.
I also noticed that at least one of the exhaust rubbers had a split in it.
Time to replace the exhaust manifolds and rubbers!
The next problem was sourcing the correct parts for the old 1977 307 chev OMC. It wasn't easy... So Randy (at the local boat shop) suggested replacing the whole OMC exhaust and inlet system with the latest, brand new Mercruiser parts. He did advise me though that the Mercruiser exhaust uses a 3 inch system and the old OMC was 2 inches.
He said that the new manifolds, risers and thermostat housing would bolt straight on - but we would have to step-down to a 2 inch system by the time we got to the transom.
To accomplish this he ordered in an aftermarket fiberglass elbow 'reducer'.
Three inches diameter on the inlet side, two inches diameter on the outlet side.
Sportfish IV is a 1977 24' Skipjack currently being restored.
Moderator: Bob Fisher
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- NEW MERCRUISER MANIFOLDS AND RISERS ON AN OLD OMC MOTOR
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Capt. Aussie Bob Fisher