2001 Merc. 150 runs hot

[jwb729]

Impeller was replaced last year. Water pickup area seems to be clear of anything that would create air being drawn into the take ups. Stream is normal, but engine temp goes right to 195 to 220. Never used in saltwater. Have not checked or replaced thermostat (stream was normal, so that ruled that out). Is there another water pump in upper block unit that may be failing and reducing pressure even though stream looks normal? Can I run the engine without a thermostat without causing damage?

 

[JUSTINTIME]

Re: 2001 Merc. 150 runs hot

t stat or blocked passages or even a bad sensor, check those out

 

[andy6374]

Re: 2001 Merc. 150 runs hot

Are you cylinder heads too hot to touch for a couple of seconds?

Replace the tstats for good measure.

Have you ever serviced any of the pressure relief valve components? If it's overheating at idle then the poppet isn't seating and if it's overheating at idle then the poppet valve isn't opening (most likely some debris stuck in the spring would cause this).

Do you have a water pressure gauge, if so what are the readings at various RPMs?

 

[jwb729]

Re: 2001 Merc. 150 runs hot

Are you cylinder heads too hot to touch for a couple of seconds?

Replace the tstats for good measure.

Have you ever serviced any of the pressure relief valve components? If it's overheating at idle then the poppet isn't seating and if it's overheating at idle then the poppet valve isn't opening (most likely some debris stuck in the spring would cause this).

Do you have a water pressure gauge, if so what are the readings at various RPMs?

 

[jwb729]

Re: 2001 Merc. 150 runs hot

The heads are hot, but not unbearable.

I will replace the T Stat - can you run engine without one?

Temp drops right down at idle and will stay right around 165 to 175 - is that normal temp?

Do not have pressure gauges, but stream looks and feels similar to a 90hp Merc. I recently owned and ran well.

One thing I will add is that the temp rises quiclky from an idle to just 2/3 power and the stream is VERY hot - not to the point of burning you, but cant hold your hand there for very long.

 

[JUSTINTIME]

Re: 2001 Merc. 150 runs hot

u can test the t-stats and poppet valves
do this and if still happens then clean passage ways and that impeller might be shot
i have seen bad impellers pump fine at idle and worse on wot