Volvo Penta AQ260A

"My 1986 AQ260A is running a 2

"My 1986 AQ260A is running a 280B outdrive that has just been rebuilt. The Boat has been idle for more then 6 months while the out drive was being repaired. After running for about 1 hour and 15 minutes the engine started to labor, slow down and stop. I cleaned the breather cap on the carb which was covered in grease. I reinstalled, ran out to fishing grounds, trolled for about two hours and while trolling the engine shut down. I started the engine again after severial tries, tried to accelerate and it shut down again. The bottom line is that after running this engine for about two hours it wants to quit. After it cools down it will start and runs fine. Help, what kind of problem do I have now? Thanks for your help in advance.}"

"I suppose starving it for air

"I suppose starving it for air with your plugged flame arrester might have burnt up some valves. I would start with a compression test of the engine.
It could be a dozen different things, but a compression test is always a good starting point.
If compression test passes,then visual inspection and typical tune up stuff. Fuel filters etc..."

Check oil level in the drive..

Check oil level in the drive..