Overheating issue on Merc 140 hp

[gpolkin]

I have an overheating issue on a 1977 merc 140hp. I replaced the raw water pump but still am having problems. I want to confirm that the water pump is delivering proper flow after my replacement.

How much flow rate should i see at the t-stat intake hose? I definitely see flow when I run at 2000 rpm but I am not sure if it is sufficient. Trying to rule this out before replacing the manifold/inspecting the exhaust shutter.

One other piece of info. The engine runs cool if I hook a hose directly to mufflers on the lower unit, hot if I run from tub of water.

Greg

 

[Bondo]

Re: Overheating issue on Merc 140 hp

I have an overheating issue on a 1977 merc 140hp. I replaced the raw water pump but still am having problems. I want to confirm that the water pump is delivering proper flow after my replacement.

How much flow rate should i see at the t-stat intake hose? I definitely see flow when I run at 2000 rpm but I am not sure if it is sufficient. Trying to rule this out before replacing the manifold/inspecting the exhaust shutter.

One other piece of info. The engine runs cool if I hook a hose directly to mufflers on the lower unit, hot if I run from tub of water.

Greg

Ayuh,.... Welcome Aboard,... Is the water level high enough to completely flood the waterpump, in yer tub,..??

I use muffs,..

The flow rate is discussed in the shop manuals, available in the Adults Only section, at the top of this forum...

I don't remember off hand, maybe somebodyelse does....

 

[gpolkin]

Re: Overheating issue on Merc 140 hp

Ayuh,.... Welcome Aboard,... Is the water level high enough to completely flood the waterpump, in yer tub,..??

I use muffs,..

The flow rate is discussed in the shop manuals, available in the Adults Only section, at the top of this forum...

I don't remember off hand, maybe somebodyelse does....

Yep the water fully covers the intake in the tub. I had the same issue idling in the lake. Slowly creeping temp. When it passed 160 I turned it off.

 

[Bondo]

Re: Overheating issue on Merc 140 hp

Yep the water fully covers the intake in the tub. I had the same issue idling in the lake. Slowly creeping temp. When it passed 160 I turned it off.

Ayuh,.... That's a few inches short of the impeller....

It's a flooded entry pump,... that why I use muffs, or in the water...

160? ain't hot,... 200? is Hot...

Are ya boatin' in Saltwater,..?? If so, pull the riser, 'n see if it's plugged up... or rotted off...

You'll probably need new shutters too,... they burn up pretty quick, without water flow....

 

[thumpar]

Re: Overheating issue on Merc 140 hp

How did the old impeller look? Any missing pieces?

 

[gpolkin]

Re: Overheating issue on Merc 140 hp

How did the old impeller look? Any missing pieces?

I just repulled the lower/lower and the impeller looks good, the keyway was still in place and it was turning when I turned the shaft. I am probably flailing but i am going to replace the water pump housing base and see if that helps. I just don't know why else I would get strong flow off the hose and minimal flow when fully submerged in a garbage can or in the lake.

Greg

 

[gpolkin]

Re: Overheating issue on Merc 140 hp

After replacing the water pump base the boat ran cool in the tub and in the lake. A little hesitation when accelerating but that will be the topic of another thread.....