Runs great for an hour or so then stops

dmiz09

Recruit
Joined
Jul 13, 2009
Messages
4
I have a '83 Mercruiser 470 3.7 and it starts, idles, and runs fine for an hour or two and then if I go to idle it stops. I can get it started again but as soon as I put it in gear and try to power up it dies. I've changed the fuel, and fuel filter. Very frustrated.
 

91Astro

Cadet
Joined
Jun 28, 2015
Messages
13
Dmiz,

I am no expert but I can tell you what happened to my '91 Mariner 150 V6....mine did the same as you described....not sure if this is a fair comparison, but may be helpful?


The oil injection system failed before I bought the boat. Being a newb, I bought the boat after seeing the motor run in a tub of water. I know now..., Anyway, as I ran it, the motor kept bogging down and finally quit. Long story short, I had 50-70 compression in the scored cylinders and was fortunate that the motor was still a "virgin" and could be rebuilt. My tech said he sees this happen 3 to 4 times per year. He disabled my oil injection system so that now I premix (50:1) my fuel and never worry about the oil injection. He removed the oil resevoir under the deck as well, giving me lots of storage room. I have all the oil injection parts in a box should I ever sell to someone that wants the oil injection system back.

I hope yours is a simpler and less costly fix.

Good luck,
Dan
 

dmiz09

Recruit
Joined
Jul 13, 2009
Messages
4
Thanks, Dan. This has happened the last three times out. It runs great for an hour or so each time. It seems like a gas issue which is why I changed the gas and took it out again. Ran for an hour and then as I was idling through a no-wake zone it quit and I couldn't get it started again bringing the second tow back to the ramp. Then I changed the fuel filter and it ran for two hours. I brought it to an idle and it quit and I couldn't get it started again bringing the third tow back to the ramp. I can't figure what is causing the issue after it runs so good.
 

91Astro

Cadet
Joined
Jun 28, 2015
Messages
13
Very frustrating...I know. As I said, I had similar symptoms. Hopefully an expert will weigh in on this soon.

Dan
 
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