1987 4.3 mercruiser overheating at high rpms

[Clarko1988]

Does not overheat at idle or slow speeds. No blockage from outdrive to tstat. I am running a full unrestrictive riser gaskets.. not sure if that has anything to do with it. Also i have check to see if tstat is working properly and it is. Am i suppose to retorqe heads aafter installing the headgaskets after a couple warm cycles? I have attached picture of riser to be okay.

 

[achris]

Re-torquing should be do on the first warm-up. Retorque cast iron heads with the engine warm. ie, new head gaskets, torqued to spec. Run engine till warm, retorque heads NOW. (Remember to loosen each bolt before re-torquing it).

As for the overheat, sounds like either a restriction between the pump and the engine (the small hose inside the bell housing comes to mind), or restricted outflow (the elbows). The only other place it could be is the water pocket cover. This all assumes you serviced the water pump when you had the drive off.

Chris......

 

[Lou C]

That also depends on which brand of HGs you used. For example some Fel Pro HGs do not require re-torquing

 

[Clarko1988]

Re-torquing should be do on the first warm-up. Retorque cast iron heads with the engine warm. ie, new head gaskets, torqued to spec. Run engine till warm, retorque heads NOW. (Remember to loosen each bolt before re-torquing it).

As for the overheat, sounds like either a restriction between the pump and the engine (the small hose inside the bell housing comes to mind), or restricted outflow (the elbows). The only other place it could be is the water pocket cover. This all assumes you serviced the water pump when you had the drive off.

Chris......

So i took the raw water hose that comes from the outdribe of at tstat and it is flowing like a garden hose. Also installed un restricted riser gaskets could it have anything to do with not having the the partially restrictive ones? Ive seen on the the web that that may be a problem too

 

[Bondo]

So i took the raw water hose that comes from the outdribe of at tstat and it is flowing like a garden hose. Also installed un restricted riser gaskets could it have anything to do with not having the the partially restrictive ones? Ive seen on the the web that that may be a problem too

Ayuh,..... I'm pretty sure that you should be usin' the restricted riser gaskets in yer set up,.....

 

[Clarko1988]

Ayuh,..... I'm pretty sure that you should be usin' the restricted riser gaskets in yer set up,.....

So that quite possibly be what is going on?

 

[Bondo]

Ayuh,..... Very possibly,....

 

[Clarko1988]

Ayuh,..... Very possibly,....

 

[Clarko1988]

Ok ok possible.. lol

 

[Clarko1988]

I may have found the issue i removed water pocket cover and the gasket was brittle and not much there. I installed new gasket and sealed with form a gasket. Will update when i take her for a spin