1972 140 hp Merc I/O running hotter than before

M

muskrat808

Petty Officer 2nd Class
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Jan 24, 2011
Messages
106
Hi - Just had my old Starcraft Holiday out for first run of the season .Temp gauge reading last year was maybe halfway between mid point and the red "danger" zone . Now its 3/4 of the way to the red zone but not yet in it . Stayed that way either at idle or higher RPMs. Preventively replaced the thermostat ,thermostat housing ( with used one ,broke a bolt on the original ) and the complete water pump end of last season . Is this increase in temp reading worrisome or maybe the new normal after the work done ?Though I would think the temp should go down assuming pump replacement was done correctly . Thanks for any input .
 
Bondo

Bondo

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Re: 1972 140 hp Merc I/O running hotter than before

and the complete water pump end of last season
Click to expand...

Ayuh,... The Raw water pump,..??

Generally,..?? Saltwater, or Freshwater,..??
 
achris

achris

More fish than mountain goat
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27,468
Re: 1972 140 hp Merc I/O running hotter than before

Check exhaust elbow and manifold for internal (water passages) corrosion and clogging....

A slow increase in temperature over time is a classic symptom...
 
achris

achris

More fish than mountain goat
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Re: 1972 140 hp Merc I/O running hotter than before

muskrat808 said:
OnllyFreshwater .
Generally ? I don,t understand.
Click to expand...

2 water pumps on a sterndrive engine...

One is the circulating pump, on the front of the engine... the other is the seawater pickup pump, in the leg.... Which one did you completely replace last season?

Chris.....
 
M

muskrat808

Petty Officer 2nd Class
Joined
Jan 24, 2011
Messages
106
Re: 1972 140 hp Merc I/O running hotter than before

achris said:
2 water pumps on a sterndrive engine...

One is the circulating pump, on the front of the engine... the other is the seawater pickup pump, in the leg.... Which one did you completely replace last season?

Chris.....
Click to expand...

Replaced thepickup pump in the lower unit of the sterdrive. So is it OK to run at the higher temp as long as the gauge doesn't enter the red zone ? Thanks
 
Don S

Don S

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Re: 1972 140 hp Merc I/O running hotter than before

No it's not safe. It's telling you there is a problem with the cooling system. You have to find it. What was the condition of the rest of the raw water pump? Did you replace the gaskets? Housing ok?
Is the thermostat stuck shut? Exhaust manifold or riser water passages plugged up? Hose kinked between the drive and the transom shield?
 
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