Mercury 500 thunderbolt overheating

[robbie2618]

Greetings,

I have a 1975 Mercury 500 50 horse thunderbolt outboard that is overheating. The telltale stream is week at low power and none at all normally at idle. At power it is intermittent and spits then steam. I have replaced the impeller, the old one looked fine also. The pump tube is connected to the pump housing and the housing all looks good. I can blow water done the telltale hose and it comes out the exhaust just fine. There is a plug on the power head and when I take it out I can blow water in there and it comes out the exhaust. I have also removed the lower section and blow water up the pipe and it comes out the tell tail and the hole in the power head when the plug is removed. Cannot figure out why water won?t pump! Any one have this before?

 

[Pigglesnake]

Re: Mercury 500 thunderbolt overheating

Greetings,

I have a 1975 Mercury 500 50 horse thunderbolt outboard that is overheating. The telltale stream is week at low power and none at all normally at idle. At power it is intermittent and spits then steam. I have replaced the impeller, the old one looked fine also. The pump tube is connected to the pump housing and the housing all looks good. I can blow water done the telltale hose and it comes out the exhaust just fine. There is a plug on the power head and when I take it out I can blow water in there and it comes out the exhaust. I have also removed the lower section and blow water up the pipe and it comes out the tell tail and the hole in the power head when the plug is removed. Cannot figure out why water won?t pump! Any one have this before?

Have you ever gotten an answer to this question ? I have the same issue with mine also. Have changed everything and yet no resolve.