Overheat question.

[Jeff Delbuono]

I have a 88 240 sorrento with a merc 5.7 and alpha 1 gen 1 drive. Im on vav in the florida keys. New impella lasr year. Risers 2 years ago. Out of water on muffs got a good flow of water out the transome. In water at idle and low rpms runs lower. At 3500 rpm runs this high. Is this too hot? Old boat with old gauges and hard to get exact temp.

 

[Espos4]

If the gauge is accurate, it seems high. Old gauges could be the issue.

How about an infrared temp gun, point at the thermostat housing and read the temperature.

Can you keep your hands on top of the risers or are they too hot?
Port side may be warmer than starboard, that’s normal.

 

[Jeff Delbuono]

I did do the 5 second test. Hot but can hold for 5 sec

 

[scoflaw]

You've got an issue if the temp swings with rpm range. That's an old boat...have you replaced your hoses, any obstruction in the transom ass, ? you probably should have done a new pump not just an impeller. The list goes on...water in, water out

 

[Jeff Delbuono]

Did the whole pump and impella. If i disconect the lines and hose water in all seem clear like i said. On muffs got a good flow coming out transom. Gonna keep investigating. Boiled thermostat and it did open. Was told also could drill a couple holes in t stat to help with flow. Thoughts?

 

[scoflaw]

Blockage if higher rpm's bring higher heat

 

[Jeff Delbuono]

Gonna get a lazer het gun and test to make sure its not faulty/old gauge. Can anybody tell me what the temp should be at Idle and under power. My 5.0 runs at 175 and not sure wht a 5.7 should be. Thinking same but dont know the danger zone

 

[Jeff Delbuono]

Has anybody else seen this. Just noticed gauge never pins out when sitting for a Night. First pic is key off. Second is key on. Does this mean my old ass gauge is off by a bit and giving me false readings

j

 

[Jeff Delbuono]

Update. So i bought a lazer heat gun. At water t stat housing running about 150 and same at risers. At idle and at 3000 rpm. Looks like a old faulty guage. Just ordered new style teleflex gauge on e bay. Who would think they would put a temp gauge on a boat with only 100, 145, 220 as readings.

 

[scoflaw]

senders are specific to the gauge

 

[Jeff Delbuono]

True. Its probably original. Gonna order a new one of those too. Damb thing is a $100 boat bucks

 

[Jeff Delbuono]

So my question i hope you can answer is. Its a 1988 5.7 mercruiser. My t stat housing has 2 sensors. I believe 1 is the temp sensor and 1 is a temp sensor alarm. If looking at motor first pic of sensor is on right side. 2nd is on left side. What is what? I have teleflex gauges on it now and replacing temp gauge with a teleflex.

 

[scoflaw]

2nd pic looks like gauge sender. Alarm wire will have brown on it

 

[Jeff Delbuono]

Thank you very much. Lazer heat gun at base of t stat reads 143. Has a 142 t stat so im going with either sensor is bad or gauge is off. Gonna start with sensor first but not sure if its 1/2 or 3/8