Boat runs great untill it reaches 160 degrees

[centerc]

I have a 1996 4.3 mercruiser in a 175-5 it starts great and runs good untill it warms up then it will not throttle/ it bogs down and wont go .it will only idle. I can let it set for 5-10 minutes then it run again. also when running the trim causes the engine to cut out. I have seen this problem on a few sites but no clear answer.

 

[tmccoy6]

Just food for thought. Sounds like an electrical issue. The confusing thing is the trim issue as well as poor run once it warms.
I think it might be an alternator problem which would explain the engine cutting out when you use the trim. Also, all electrical componets show weakness when the get hot. For example a engine may run ok when cold, but if a coil is showing signs of weakness it will show once it get hot as heat increases resistance.
The best money bet is the alternator. Take the alternator off and run it by a auto parts house and they can check it on thier machine. That will rule out that issue. Hope this helps!

 

[Firerooster]

Also check the wiring from the alt. It may have a weak fusible link that loses contact when hot.

 

[centerc]

Took it buy the repair shop hope its not too bad I replaced the coil could be the alt but it does not run the batt down

 

[douglee25]

It could be a faulty temp sensor for the ecm, not the temp sensor on the dash. The temp sensor thinks the engine is over heating and it goes into limp mode.

Doug

 

[centerc]

Got it baCK TODAY They replaced the fuel pump ran great for a few minutes then worse. When you hit the trim up or dwn it cuts out thinking rotor cap/ button

 

[centerc]

Got it Back again ... They Replaced the Ing with a thunderbolt 4 it ran great for an hour hopefully it stays good .