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1983 Mariner V6 150 hp overheating

R

rlt

New member
Have had this good motor all its life. Engine probably has less than 100 hours on it. Now, after laying idle all summer in my garage, it overheats when I run it on the lake.
Here is what I observe:

Water telltale is sporadic at idle speed. At higher speed, no water gushes from the two exhaust ports like it always has in the past. High temp alarm comes on quickly at mid rpm range. Yet, I have pretty good water pressure on the gauge.

Checked so far:

Opened up flanges that house the thermostats, all clear here. (removed the thermostats years ago due to corrosion)

Telltale orifice is clear

WP Impeller looks in good shape, including not being loose on the hub or spinning on the shaft (key is good).

Problem almosts suggest I have a plug in the jacketing somewhere downstream of the pressure tap.

Any thoughts or ideas would be most appreciative
 
Water telltale is sporadic at idle speed....removed the thermostats years ago...
Click to expand...
When was the impeller last replaced...3 yrs max between service. You may have debris under the waterpump hsg. Did it suck any sand or mud in the past? If it is used in salt water then the water jacket may be full of corrosion restricting water flow.
 
Impeller last changed about 3 years ago, but I am planning to change it out anyway---so will try that. I think, from your comment, I should take a look on the suction side of the pump.

On the water jacket itself, I can blow a good air stream through the engine from the tell tale backwards.

Thanks
 
Suction side of the pump was found to be completely clean and free of debris. So, its on to the impeller. The pump case is in good shape.
 
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