470 over heating looking for help

[Blue t]

I have a 1988 sting ray that I think is over heating 200deg. Here are the things I have done.
1. changed sea water pump
2. cleaned the 4" heat exchanger
3. new hose from the transome to the heat exchanger
4. check the timing
When I opened the radiator cap it was empty and the coolant had been pushed in to the over flow tank. I pulled the exhaust elbow and it had been siliconed on which also had the coolant passages blocked. I also pulled the bellow and it was burned on the inside. The person I boght the boat from said he replaced them but Im not sure he did. He also said he had the head reworked and a new head gasket but I am going to do a compression check to eliminate the head gasket. Is there any thing else I can check?

 

[stonyloam]

Re: 470 over heating looking for help

While the reservoir is empty take the opportunity to remove the reservoir/exhaust elbow assembly and thoroughly clean out the seawater passage, that could be restricting your flow. Replace the gasket and do a cooling system pressure check along with the compression check (Autozone will lend the tools). Good luck.

 

[EddiePetty]

Re: 470 over heating looking for help

...and following stonyloam's advise:

While you're cleaning the seawater passage of the reservoir/exhaust elbow/'riser', be 100% certain to look down in the exhaust passage for remmants of an expired shutter (flapper) valve. Also consider removing the propeller and examining the outboard portion of the exhaust for similar obstructions.

Were there any pieces missing from the removed pump impeller? Did you account for any missing pieces? Did you remove the forward end cap of the heat exchanger when cleaning it? If negative to any of the above, please do so. Have you verified the correct and functioning thermostat? Additionally, examine the rubber hose leading from the lower unit to the transom plate (outboard) for kinks and/or deterioration.

 

[dry dock]

Re: 470 over heating looking for help

those passages are suppose to be blocked use the correct gasket your engine coolent is going out exahust you should download the engine manuel from this fourm.......good luck

 

[Blue t]

Re: 470 over heating looking for help

Here is what I found tonight. There was no thermostat and there is no shutter. I can not see any pieces of the shutter but I am going to look with a mirror this weekend. I am still going to do the compression and coolant check and will post the results after. I put my water hose down the lower exhaust pipe and it flows fine out the exhaust. Thanks for the help maybe one day I can pull my kids behind the boat I think they are getting more frustrated than me.

 

[stonyloam]

Re: 470 over heating looking for help

The seawater passage is the pipe fitting on the exhaust elbow, just behind the reservoir. The seawater exiting the heat exchanger goes through a hose into that fitting. The water circulates around and out into the exhaust (cools the elbow and exhaust gases). If the internal passage becomes clogged it can restrict the seawater flow. Try hooking the hose up to that fitting to make sure you have a free flow there.

 

[Blue t]

Re: 470 over heating looking for help

With the engine trimmed up should I see light looking through the lower exhaust?

 

[guyaverage]

Re: 470 over heating looking for help

Depends, where are you shining the light, and where are you looking?

No thermostat...riser siliconed on...sounds like the previous owner did some ham-fisted DIY'ing on this beast. Check the compression, clean up the gasket surfaces, put on new gaskets (dry, no sealant) and get a proper Merc 160 degree thermostat in there, without one its going to overheat, or at least run warmer than necessary, no matter what you do to it.

If there are still problems after that, you might want to revisit that head gasket (easy for me to say...).