Have Boat Questions? Ask a Boat Repair Expert.
Hi my name is Mike, can we start by answering a few questions.....
How much coolant did you have to add to expansion tank?
Have you checked the output water after it's been running for a while?
Have you checked/felt the generator to see if it's getting hot?
Shutting down after several minutes of running is most indicitive of the generator getting hot enough for the exhaust temp sender to shut down the unit.
If it is not actually getting hot then it is possible that the exhaust temp sensor is failing causing the unit to shout down. the sensor is located on the exhaust manifold or riser/mixer. If the generator is not getting hot then you can try disconnecting this sensor and running the generator to see if keeps running.
Let's start here and see what you come up with and we'll take it from there.