Mercruiser OVERHEATING...Help!?

[robzifer]

Hello,

Got a 1981 260 V8 Mercruiser that is overheating bad...

Engine has:
New center riser exhaust manifolds
Brand new Thermostat housing
Brand new Thermostat
Brand New water impeller
Brand New Temp Sender
Brand New temp Gauge


Checked:

ALL hoses are not blocked
Getting good water flow out the back of the boat
Exhaust Elbows are cool to the touch
Good flow from the water pump
water pump condition

Problem:
Boat heats up to above 220 either in the water at idel or full speed or out of the water with harden hose hooked up.


What do you guys think? could it be a blocked engine block problem??? If so what can I do about it? I already took off the water pump and therm housing and see no blockage but cant see all the way in..

 

[Bt Doctur]

Re: Mercruiser OVERHEATING...Help!?

any chance the therm is held in place with a plastic ring.there are usually 2 cutouts that must be lined up.other thing is remove the backplate from the circ pump to check for a broken shaft.

 

[robzifer]

Re: Mercruiser OVERHEATING...Help!?

yes the thermostat is held in place with a metal right on to of it.. did not notice any cut outs though..i guess ill open it back up to check...

Took off the water circ pump..looks good!

 

[Bt Doctur]

Re: Mercruiser OVERHEATING...Help!?

yes the thermostat is held in place with a metal right on to of it.. did not notice any cut outs though..i guess ill open it back up to check...

Took off the water circ pump..looks good!

remove the backplate to check the pump shaft to impeller

 

[robzifer]

Re: Mercruiser OVERHEATING...Help!?

yes, did that... took off the back plate..no problems.

 

[Bt Doctur]

Re: Mercruiser OVERHEATING...Help!?

check post #5 in this thread, shows an insert.
http://forums.iboats.com/showthread.php?p=2913882#post2913882

 

[robzifer]

Re: Mercruiser OVERHEATING...Help!?

Yeah mines different... mine looks like the one in the below link ..the gold ring at the bottom of the photo

http://bpi.ebasicpower.com/ebinfo.php?pn=GLM13221

 

[Bt Doctur]

Re: Mercruiser OVERHEATING...Help!?

thermostst element facing inward toward the motor
hoses routed correctly
you say there is flow out the manifolds and risers so why is it not entering the block?
circ pump shaft and impeller you said were ok.could the circ pump be reverse rotation instead of bi-directional?

 

[robzifer]

Re: Mercruiser OVERHEATING...Help!?

thermostst element facing inward toward the motor
hoses routed correctly
you say there is flow out the manifolds and risers so why is it not entering the block?
circ pump shaft and impeller you said were ok.could the circ pump be reverse rotation instead of bi-directional?

Not sure what you mean by "thermostat element facing inward toward the motor"

Hoses are routed as" two coming off thermostat cap to bottom of manifold and the ones coming off the T with the ball valves going to Top of elbows

Yeah Impeller and Circ pump are good... Not sure on the Bi=directional or not but the blades of the circ pump don't seem to be slanted in any one direction at all just flat..so guessing its bi- directional?


Could part of the block be clogged and just not allowing the water to flow though? not sure how to check it though cant see that far into it

 

[thumpar]

Re: Mercruiser OVERHEATING...Help!?

What temp is the thermostat?

 

[robzifer]

Re: Mercruiser OVERHEATING...Help!?

140..brand new.... does same thing with the old one installed also..both are 140