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1977 omc 351 overcharging/engine stall

bassmama

New member
first off i want to say hi to all the more knowledgable people then myself who offer answers, opinions, and suggestions, thank you. ok guys so i have a 1977 apollo with a 351, omc outdrive. after some repair to the outdrive and putting it back in the water i went cruising out of the marina. mind you its a no wake zone so its 5 mph. this first run out it made it approx 3 miles and all of sudden boom engine stalls. not a sputter kind of engine stall, but like you turned the key off. so ended up having to tow it back to the slip, cuz batteries didn't have enough juice to start. upon inspection the regulator was melted. all that goop melted down onto the engine, so i replaced that and took it out again and paid attention to the voltage gauge. it seemed to do fine in the 5 mph zone but as soon as you gave it more throttle the gauge pegged and again it stalled. i have the original petrolite alternator but it is still good, but i read something about the resistance and something about running a jumper wire. anyways any thoughts anyone wou;ld be appreciated
 
I don't know if this really applies to OMCs of that vintage, but I know on mine they used a sense wire to sense system voltage and that is what the voltage regulator went off of. Now this sense circuit could build up high resistance and read lower than the rest of the system, a tip off that something wasn't right was that even though the batteries are adequately charged, the voltmeter on the dash read low after fixing this over voltage issue.
The cure was (I got this from ARCO marine when I got a new ARCO alternator) was to disconnect the Sense wire at the alt (marked S on the alt, just tape it up in the harness). Then make up a 14 gauge jumper wire from the large B+ terminal (large orange wire) to the sense terminal. Once you do this the charging voltage should return to normal (14.2 V or so) mine was up at 15.5 V at the batteries. The low voltage at the dash voltmeter and guages was another problem, the feed to the fuse box was undersized, and I ran a supplemental 8 gauge wire (fused of course) from the battery switch to the pos terminal on the fuse box, that took care of that one.
The first problem was definitely due to the OMC engine harness wiring, the second may have been peculiar to my particular boat.
 
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