Problem persists need advise

[Omc-nightmare]

Here is the run down so far I own a 16 foot pennyan with a 2.5 liter omc engine. I have been having an issue with stalling on the lake. The first thing I did was replace the carburetor it sounds better but still no luck. While running the boat on the muffs I noticed it tried to overheat. So I replaced the impeller On July 4 on the lake it ran better for longer. I was watching the temp gauge while the temp was below 160 the boat ran great as soon as it reached that threshold the engine started to bog. I naturally pulled back on the throttle as I did the engine coughed though the carb and would not start. After a few minutes I was able to get to turn over again but it made a screeching sound I revved the engine and it went away. My question is could this be a problem with the head? Would it be worth taking a look? Any suggestions at this point I am thinking rebuild.

 

[Omc-nightmare]

Also if a mod or admin can assist me in changing my user name let me know

 

[Howard Sterndrive]

the head? I don't follow.

1. Start with a compression test.
2. when it stalls, spin the spark plugs out and look for signs of water in the combustion chambers
3. electrical - check voltage to coil + (referencing batt neg, NOT coil neg.)
4. check ESA if equipped (no year provided)
5. fuel system - filter, tank vent, anti-siphon valve

 

[john cole]

i wonder if it isn't vapor locking?

 

[vinnie1234]

The screeching could be the alternator belt. If it isn't tight, you could be pulling charge from the battery and stall when voltage gets too low.

 

[Omc-nightmare]

The belt does seem lose but it is charging my voltage meter goes from 12 to 14 when started. I was thinking freeze damage that's why I said the cylinder head. The problem happens when the engine is at operating temperature, will I need to warm the engine up to do a compression test?

 

[vinnie1234]

A compression test should be done warm. To diagnose the head, just pull a spark plug. If you have a leak severe enough to do what you said then you will have 1 or two spark plugs shiny and clean looking. A note on the alternator: every time a cylinder fires, the engine accelerates rapidly. A loose belt will often slip more at higher RPM for a variety of reasons. At least tension the belt properly and see if it makes a difference. To confirm, you can run a voltmeter with the boat to see what happens.