CONTINUOUSWAVE

I have a 2005 150 Sport [with a Mercury 60-HP FOURSTROKE outboard engine]. The engine runs for twenty minutes and quits. After 10 minutes [rest it can be re-started] and runs again for twenty [minutes] and quits.

[Give] suggestions [of the cause of this behavior].

There are two likely causes:

--in the fuel system there is some malfunction that causes the engine to run out of fuel after about 20-minutes; a period of rest removes the malfunction; the cycle starts anew; perhaps there is too much vacuum restriction in the fuel delivery system. Is there a vent on the fuel tank? Check the vent to see if it is obstructed or closed;

--in the electrical system there is some malfunction that causes the engine to stop running due to loss of electrical signals; this could be caused by heat; a period of rest allows the affected component to cool, and it begins to work again; many electronic assemblies are sensitive to and will be affected by heat.

If the onset of the engine stopping is gradual, suspect a fuel problem. If the engine cuts off like you shut off the ignition switch, suspect an electrical problem.

it seems like a fuel problem, maybe vapor lock?

Can you explain how an engine that is running is stopped by "vapor lock"?

[Three month's later with no replies from the OP]

Is the fuel tank vented?

This thread has been dormant for almost four months with no reply from the OP to questions. Thread closed.