Mercruiser 260 V-8 - 1986 Stalls after 20-30 minutes

[8001sw56]

I have a 1986 Chris Craft with a Merc 260- V8. It is the open system cooling. It starts great, & runs great for about 20 min. Then it just stalls. I pulled off the fuel line & cranked it & gas came out. I haven't checked the pressure yet. It usually starts again, but has to sit for a while. Oil pressure & water temp are ok.

It has new plugs, dist cap, rebuilt carb,new gas filter, water separator, timing checked.

I have heard everything from plug wires, coil, vapor lock, exhaust leak, thunderbolt ignition. Being on a limited budget, I would like to have some input on the most likely direction to go.

I know "limited budget & old boat owner" don't go together. I worked on these old GM engines when I was younger, so I know just enough to be dangerous.

Help.

 

[Bondo]

It usually starts again, but has to sit for a while.

Ayuh,.... Welcome Aboard,.... Durin' the time it won't start, it's missin' either Fuel, or Fire,...

If ya diagnose it durin' the time it won't start, you'll know which way to go,....

 

[harleyman1975]

It is possible this issue could be fixed by replacing the pick up coil in the dist. (I am assuming it is loosing spark) If that doesn't fix it I would move on to the ballast resistor/or resistor wire and check for power to the coil next time it fails, If 9 volts present with key on then I would try changing the coil...could be coil is getting hot and suffering thermal breakdown. Let us know if you get it solved. There is more places to dig but I would start with the most common and easy to change parts. just my .02

 

[JaCrispy]

Check your fuel tank vent isn't clogged and routed properly.

Next time it stalls, try loosening the fuel filter and listen for a "hiss" sound. If you hear it, the fuel system is pulling a vacuum.

 

[bruceb58]

Better yet, run with your gas cap off. If it runs longer than your time right now, start inspecting the tank vent.

 

[8001sw56]

Two good ideas! I'll try them both.
Thanks,