Cooling system question for 3.0 mercruiser

[airtime63]

Thanks to the help of Stevieray and Don S. I have narrowed down the problem. I have a mercruiser 3.0 with an Alpha 1, year is an 87'. I was getting very poor water flow throughout the engine and it was getting hot.
I have removed the lower unit and the impellor is shot. I also plan on replacing the thermostat and sending unit because the gauge does not work.
My question is, I had the whole stern unit water pump replaced only two months ago. I ran the boat for one weeks worth of boating on vacation. It ran great. I was getting it ready to take out one last time and I had this problem arise. What else could be causing my water pump and impellor to fail so quickly? I am at a loss and would love some insight. I want to find the root of this problem for burning up water pumps. The boat was run in fresh lake water. Thanks in advance

 

[Haut Medoc]

Re: Cooling system question for 3.0 mercruiser

Was the impeller wasted from overheating?
Have you started it out of the water without a supply of water to the drive?
Could someone else have started it without water supply?
Did it overheat at all after the impeller/pump was replaced?
A plastic bag over the inlets can do damage quickly....
Replace the impeller & get the sender/gauge working & see if it reoccurs.....JK

 

[cr2k]

Re: Cooling system question for 3.0 mercruiser

NEVER repeat NEVER run an engine without water. Not even to "just see if it will start". It takes less then 15 seconds to fry a water pump impeller.

Also check to housing. See if it has any signs of melting top and bottom. If so you need to replace the whole thing. Many use soap or glycerin to lube the new impeller during replacement. I have used silicone spray for decades with no problems. Turn the vertical drive shaft clockwise when putting on the top housing.

Make darn sure you engage the water tube when reinstalling the lower unit. or you will be pumping water in to the lower unit and not to the engine.

If your impeller has any broken or missing blades (always find all the pieces) you can have overheating from the pieces getting lodged in the cooling system.

If you have power steering they most likely will get jammed in the heat exchanger, usually found along side the engine about the oil pan level.
or on the back of the engine crosswise.

 

[Bondo]

Re: Cooling system question for 3.0 mercruiser

Dude,......

This thread is over 3 Years Old,.......

 

[bcschro]

Re: Cooling system question for 3.0 mercruiser

thank God he answered it cause it just helped me.