mx 6.2 mpi cuts out
 

hi everyone i have a 2006 6.2 mercruiser mpi that has covered 80 hours,mostly under 4000 revs on a 21 ft cuddy. i have now had a new prop fitted which has improved the handling and now i can use the boat up to 4700 revs easily. the problem i have is that after 30-40 mins of high rev running the engine cuts out,as if you have pulled the kill switch out. at low revs anything under 3000 in rough or smooth seas the engine is fine. when it cuts out if you dont move the throttle the engine dies,but if your quick and you do pull the throttle back the engine will keep running,it always starts straight away again ,i have disconnected the kill switch and have had the lap top pluged in and there are no fault codes. i have read that some of these engines have had problems with the ecm/ecu getting hot a shutting down,but i am concerned that there are no air vents to the engine bay (apart from the engine bilge blower)could the engine be starved of air,although there are over 10 of these boats made with inboards and as im aware they are all ok.........any ideas you may have will be appriciated many thanks

I had a problem with my port 6.2 in my Powerquest 32 SC when it was new. It would run well some time then cut out at higher rpm. It took a while befroe it was discovered that the crank sensor was not "seeing" the magnet mounted on the lower pulley. When we realighed that it ran fine and is still runinning well 270 hours later.