1979 OMC 120hp still stalling after a while

bradrulz

Cadet
Joined
Jul 18, 2004
Messages
17
hi, might recognize me from previous posts. still stalling but i think i'm getting really close now.<br /><br />recap: my '79 OMC stringer (4 cylinder) unfortunately has a worn or broken ring in number #4 cylinder. it sure sounds good running, has good fire, and very very little blow-by, so i'm trying to get her running as best as can be to finish up the season. may have it rebuilt this winter.<br /><br />After about an hour out on the bay (SF Bay), kept losing rpms until she stalled. would crank right back up and crawl a little further before doing it again. Thanks to many helpful replies and other posts i read, it sounded like it could be a failing coil. it looked original anyway, so i replaced it. next time out it was as if it was starving for fuel, wouldn't start unless throttle was full on, sounded good when on, then would stall after a while, and very hard to restart. I figured now there was a fuel system problem, so i bypassed the built-in gas tank and fuel line by hooking up an auxiliary tank, with pump bulp straight to fuel pump. filled up with new 89 octane fuel and took her out today.<br /><br />she cranked up just fine, absolutely purred with a little throttle, but idle was a little rough. did well through 5mph no-wake zone, but shortly after opening up WOT, she stalled. I warmed up at the dock about 15 minutes before pulling out to test at WOT. <br /><br />I'm thinking next step would be the fuel pump. Boat's paperwork shows "pump kit" back in 2001, i'm guessing that *might* be fuel pump kit with gaskets or something. Might be time to just put a new fuel pump on. That's the direction i'm thinking, however I would really love any feedback to something else i could be overlooking.<br /><br />Thanks so much, i really love this forum.<br /><br />-brad
 

Boomyal

Supreme Mariner
Joined
Aug 16, 2003
Messages
12,072
Re: 1979 OMC 120hp still stalling after a while

From your description, sounds like it could well be the fuel pump. My original pump lasted 28 years with a few years rest in between. Last year it started acting up, usually at high rpm/load. Some trips out it would work fine. I actually had to get towed in once. Took the pump apart, looked fine, put it back on but ordered another pump anyway. Two trips later it finally died and would not restart. Luckily I had thrown the new one onboard and was able to change it on the spot.<br /><br />As to your 'pump kit', my understanding is that repair kits for marine fuel pumps are not offered. At least that was the case with mine. It's a safety issue.
 

bradrulz

Cadet
Joined
Jul 18, 2004
Messages
17
Re: 1979 OMC 120hp still stalling after a while

Boomyal, i understand followups are a courtesy to these posts. therefore, thought i'd followup to announce i sold my boat to another enthusiast. he has it in his eye to fix her up, so i passed on the project, and the fun. <br /><br />I'm getting ready to post a general post to inquire whether i should buy this 1972 Hydroswift I just found. Hope i'm lucky enough to receive your help in the future, man!<br /><br />cheers!
 

rockhard981

Cadet
Joined
Oct 31, 2008
Messages
6
Re: 1979 OMC 120hp still stalling after a while

i was wondering if someone can help,i have a 1979 omc 120 thats seized,i was wondering if i can bolt up another engine (like a 2.5 chevy) ,any advice would be great.
 

chiefalen

Captain
Joined
May 18, 2008
Messages
3,598
Re: 1979 OMC 120hp still stalling after a while

Rock start your own post i just did what you want to do, last month.
 
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