Merc 470 Coolant Leak from exhaust

[cshirley]

Ok, I've been doing some reading and I know its either the exhaust manifold, riser, head gasket, or a cracked block. When I pour coolant in, it comes right out the exhaust and I'm not talking a drip, it literally dumps out. I put the hose in it to fill it and it never overfills, just runs straight out the exhaust.

I pulled the heat exchanger and checked it (pretty self-explantory) and it was good, could be better as a 4" but thats down the road.

I pulled the exhaust riser and the other part where you pour the coolant in (not sure what its called). Looking at the opens top ends of the manifold, if I pulled the thermostat and sprayed my hose directly into that hole, the water comes out of the small rectangular ports where the riser bolts up....

I pulled the manifold completely off but I'm not sure exactly how to test it, if I spray water in the thermostat hole, should it come out of the rectangular ports matching up with the riser (I'm thinking not as this would be the seawater side).

Thanks for any help!

Curtis

 

[Don S]

Re: Merc 470 Coolant Leak from exhaust

There are several different setups on the risers and manifolds over the years. You don't seem to have posted a year, but even that won't really help.
Do you have a picture of your setup you could post?

 

[cshirley]

Re: Merc 470 Coolant Leak from exhaust

The boat is a 78 but I think the engine is newer. The thermostat in front under the part where you pour the coolant. I don't have the serial number with me,