Merc 5.7L overheating issue

[shughes12]

I have a 88 merc 350 raw water cooled alpha 1 gen 1 and I cannot pinpoint my overheating issue.
The work ive done:
Impeller/housing, checked all lines, back flushed to make sure nothing is clogging oil cooler, Tstat, circulating pump, cleaned out the risers, checked the gauge, temp sender. Hit the block with a temp gun and was showing 200°. What else am I missing??

 

[Scott Danforth]

how much water flow do you have coming from the raw water line to the thermostat housing? at idle, is should shoot up about 10" or so. you should be able to fill a 5 gallon bucket in about 20 seconds or less with the motor at 1000 RPM

overheating is a lack of flow. either flow into the motor, or flow out of the motor.

 

[Bt Doctur]

if you replaced the wp base ,it is possible to install the gasket reversed

 

[j cat]

I have a 88 merc 350 raw water cooled alpha 1 gen 1 and I cannot pinpoint my overheating issue.
The work ive done:
Impeller/housing, checked all lines, back flushed to make sure nothing is clogging oil cooler, Tstat, circulating pump, cleaned out the risers, checked the gauge, temp sender. Hit the block with a temp gun and was showing 200°. What else am I missing??

so you inspected the water cooling on the engine .. now inspect the timing distributor ....
do you replace the out drive water pump ..setup the impeller clockwise ...

 

[achris]

Water pocket cover...

 

[johnkom]

I chased a cooling issue one whole season. Out drive pump and housing replaced. Bore scoped all the cooling hoses. Even pulled the engine water pump apart to make sure the impeller wasn't slipping on the shaft. Eventually found the v-belt on the front of the engine was varnished and slipping at high speed.

Don't forget the basics.

JK