Mecury BlackMax 175Hp, Constant Beep and Overheating

Robertse

Seaman
Joined
Jan 9, 2024
Messages
57
Hi, I Mecury BlackMax 175Hp, which Constant Beep and Overheating. I have replaced the impeller water pump, it has a strong pee (pumps water strongly), howver the water coming out of the pee hole is very hot. All help will be respected. Thanks in advance.
 

Dukedog

Captain
Joined
Oct 6, 2009
Messages
3,435
do you have a water pressure gauge?... if so need readings at idle, mid range and wfo.........
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,040
Did you replace the thermostats? Rebuild the poppit valve?

A hot telltale is a sign on a lot of motors, that the thermostats are not working properly, or the cooling passages have a blockage.
 

Dukedog

Captain
Joined
Oct 6, 2009
Messages
3,435
when ya guessin' with an over heat problem and no pressure guage... replace "complete water pump"(not jus impeller), poppit kit and replace both t-stats... its relatively cheap maintenace anyway... then install a guage....... jmo.
 

Njsloans1

Cadet
Joined
Sep 9, 2024
Messages
6
My 150hp Saltwater was doing that. I changed the impeller, 2 thermostats and poppet valve. My thermostats were completely corroded and blocking the passage ways. Problem solved.
 

Robertse

Seaman
Joined
Jan 9, 2024
Messages
57
My 150hp Saltwater was doing that. I changed the impeller, 2 thermostats and poppet valve. My thermostats were completely corroded and blocking the passage ways. Problem solved.
Thanks, I have the Thermostats which seems fine, but I will replace them. Then the poppet valve.
 

Robertse

Seaman
Joined
Jan 9, 2024
Messages
57
Thanks, I have check the Thermostats which seems fine, the open when heated, I also flushed engine via the Thermastats holes when I took them out. It was clean. However I have just ordered new Thermastats and eplace them. Then if there issue is still there I will also replace the poppet valve.
 

Robertse

Seaman
Joined
Jan 9, 2024
Messages
57
Thanks, I have the Thermostats which seems fine, but I will replace them. Then the poppet valve.
Thanks for your reply. I have checked the Themostats which are fine and clean, the open up in a pot of boiling water, I still ordered new Themostats, but for the time being, I removed the Themostats and run the engine, it still runs hot, the alarm is going off
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,040
Those motors are not made to run without thermostats.

Is the poppit valve working properly? It should open at about 2000RPM and allow a whole lot more cooling water thru the block.

Put a torque wrench on the head bolts and check 'em for tightness. Sometimes they can get loose and allow compression to leak into the cooling system causing overheat.
 

Robertse

Seaman
Joined
Jan 9, 2024
Messages
57
Thanks Chris, Note I will not run the motor without the Thermostats. I hope I didn't damage the engine as I ran it for about 30 minutes without the Thermostats... I have already torque the head bolts to 30 lb. ft. (40.5 N·m) then turn an additional 90°.
 

Robertse

Seaman
Joined
Jan 9, 2024
Messages
57
Those motors are not made to run without thermostats.

Is the poppit valve working properly? It should open at about 2000RPM and allow a whole lot more cooling water thru the block.

Put a torque wrench on the head bolts and check 'em for tightness. Sometimes they can get loose and allow compression to leak into the cooling system causing overheat.
Hi Chris/Team, I have now replaced the poppet valve,
 

Robertse

Seaman
Joined
Jan 9, 2024
Messages
57
Hi Chris/Team, I have now replaced the following with new parts; poppet valve, thermostats, impeller (water pump). I also took off both Heads, inspected and cleaned the water passage ways. I have checked the new thermostats and placed them in boiling water, and the slowly open up. The head gaskets looked fine, there is no breaka or crack in the gaskets, so I put the heads back on and torqued the heads to 40 pounds. I flushed the engine; via, thermostats housing and tube (both directions while the thermostats was off), both poppet water jackets holes (while the poppet valve was off), reserve flush via the tale tail peeing hole, water run through all these above sections fine and came out from the other direction…The internal oil tank is full, I even remove the cap and placed it upside down to trick the sensor, I also disconnected the oil tank sensor to see if that was causing the beeping, it was not causing the beeping, as the beeping sound was still occurring.

After all this I still get constant beep, and the water coming out of the tale tail is hot and the heads become hot. Sometimes the beep is every millisecond and sometimes the beep is constant. One thing I noticed, while the leg was off, during the impeller replacement, I connected garden hose at the bottom of the water tube which runs up to the engine, it was pushing water strongly out of the peep (tale tail) hole and at this one stage there was NO warning beeping. But when I put the leg back on, the beeping occurs. The next thing I will do is a compression test.

I am lost because I tried all listed above.

Warm Regards,
 

cyclops222

Lieutenant Commander
Joined
Mar 21, 2024
Messages
1,804
So No lower unit AND a garden hose feeding the cool water tube to the engine works fine ?
Could be the exhaust system casting is blowing hot gases all over the pumping system down there ?
What else is left to heat up the water so much ? Geezer engine problems.
 

flyingscott

Fleet Admiral
Joined
Apr 8, 2014
Messages
8,145
Was the old impeller in 1 piece? did you check the sensor itself? Do you know if that is a 2.5 litre? If not somebody here might know.
 
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