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M60 Thermostat

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MarinerScott

New member
Hello,

I'm overhauling a mid-1980's vintage M60 3 cylinder Mariner (Serial A110787). The block and exhaust side covers have a place for a poppet valve and thermostat but there was not on installed in this motor when I took it apart. There is a newer gasket on the exhaust side, I'm wondering if someone had previously removed the thermostat and poppet and did not reinstall before reassembling. Is this motor supposed to have a thermostat and poppet?

Thank you for your help,
Scott
 
Assuming that's the same 49 cube triple Merc made for years, the t-stat SHOULD be removed and tossed out. Why? The impeller is way too small for that motor which tends to fry its top cylinder. (All five of those in my shop were damaged that way.)

You should also seal off that useless water flow to the fuel pump so it too will go to the block where it's desperately needed. The water flows out from a fitting on the lower right side of the adapter then goes to the fuel pump. Plug that hole and your motor will thank you.

Jeff (a Merc triple lover despite what most people say about them)
 
Excellent tip Jeff. Thank you! The fuel pump still has the water fitting connected. This motor did get overheated and dispite a couple new water impellers, I still get very little water out of the "telltale" while at idle. Good flow engine speeds above idle but a little concerning. This may take care of it, I hope. Scott
 
Oh, one other thing. The interior baffle plate on the exhaust side that houses the thermostat and poppet, looks to be warped. Outside exhaust cover is OK. I can likely tighten the bolts upon reinstallation and flatten it out. Should this be machined? Is it possible to machine this bow out and is it worth doing to avoid breaking the baffle?
 
Without the poppit valve will you get the correct pressure for the telltale to indicate ????-------Just a question.
 
Yes, I think it will tighten down ok. Thank you. Good question on the telltail pressure/indication. As best I can tell from looking at the block, there is a 1/4 inch hole in the base of the block-intermediate housing that will restrick the water flow to the telltale. There must be less pressure to the telltail with the poppet and thermostat removed and the only restriction is this 1/4 inch hole. Perhaps removing the water flow to the fuel pump will help and provide a better indication of water flow at idle. Thoughts?
 
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