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Alpha one 260 sputtering/intermittent stalling issue

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Bomburly

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I have a Mercruiser Alpha one 260 from the 1980s that has been having this issue for 3 seasons now. It’s been into a mechanic who cleaned the carb and had it running at the shop for hours. No issues.

however we take it out and cruise with it and somewhere between 30 and 45 minutes of cruising it starts to sputter and backfire. Eventually getting really rough and stalling.

let it sit for 5 minutes and it starts up and will idle and run at low rpms for 5 to 10 more mins before sputtering starts again.

let it sit for an hour or more and it will cruise for 45 minutes again.

we are at a lose and don’t have money to throw at it. We need to figure this out on our own at this point.

does anyone have any suggestions?

thanks,
Kevin
 
Dump the contents of the fuel filter into a wide mouth glass jar and let it sit for a half hour or so.
Gas should be clear but colored.

IF there is a demarcation line and the contents have separated into two layers, the bottom layer is water.
If the gas (top) layer is cloudy, the quality of the gas is compromise.
 
When contaminated fuel sits in tank it stratifies.... run the boat and it can mix back. Depending on how much crap in gas and height of fuel pickup above bottom determines what exact kind of fuel you get as it runs. Another possibility is that the ignition coil is overheating, but you said it ran OK in the shop so.... P.O.E. check fuel.

After fuel check... loosen fuel filler cap... you may have a clogged fuel vent, but then again this should have shown up in the shop if they did the test they said they did.
 
Last edited:
Thanks for the replies Capt Bob.

Yea it’s hard to troubleshoot an issue that only surfaces long after the motor is at temp..

I will check the fuel today. How hot should the coil be getting? It is to hot to touch when cruising, and probably 140f when idling.
 
sandkicker said:
When contaminated fuel sits in tank it stratifies.... run the boat and it can mix back. Depending on how much crap in gas and height of fuel pickup above bottom determines what exact kind of fuel you get as it runs. Another possibility is that the ignition coil is overheating, but you said it ran OK in the shop so.... P.O.E. check fuel.

After fuel check... loosen fuel filler cap... you may have a clogged fuel vent, but then again this should have shown up in the shop if they did the test they said they did.
Click to expand...

Here are a few pictures of the fuel after letting it sit for a few hours. There is not visible separation, but i did notice some debris at the bottom of the container.

IMG_0924.jpgIMG_0923.jpg
 
Bomburly said:
Any reason fuel issue like this would not cause issues until 45 minutes of cruising?
Click to expand...
I doubt that this is fuel related.

Bomburly said:
Yea it’s hard to troubleshoot an issue that only surfaces long after the Engine is at temp..

How hot should the coil be getting? It is too hot to touch when cruising, and probably 140f when idling.
Click to expand...

A coil will produce heat. However, if it's getting extremely hot, it may be bad.
Try replacing it with the correct coil for your ignition system.

.
 
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