Merc Exhaust manifold water flow

[saltwater_cowboy]

Got a 5.0 Mercruiser engine in a ski boat and its the first inboard I have seen with two sets of water pipes going to the manifolds.<br /><br />Looks like water enters the manifolds at the front like normal but also there is a hose going to the bottom of the manifold in the middle also. <br /><br />Boat appears to run ok but somewhat hot and the exhaust note is quite loud as if not a lot of water is flowing out through the exhausts.<br /><br />I'm just thinking that at some point some one has altered the cooling for the manifolds and a lot of the pipe work seems non standard.<br /><br />Anyone care to comment.

 

[tommays]

Re: Merc Exhaust manifold water flow

with out noing exactly what engine you have like a merc # it would be hard to say<br /><br />its been done many different ways<br /><br /><br />you need to be sure the raw water pump is good and that the manifolds/elbows are not so old there blocking the water flow OUT of the motor<br /><br /><br />tommays

 

[Chris1956]

Re: Merc Exhaust manifold water flow

Jay, My '88 Mercruiser V6/Alpha has a similar setup. When the engine thermostat is closed, excess water flows through the top fittings to the risers. After the thermostat opens, water flow is through the block and then to the lower fittings on the manifold. Excess water can also still enter the upper fittings to the risers. There are plugged holes on the top of the manifolds also.<br /><br />Not sure if this helps!