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1979 Marine Power 350 coolant in exhaust

M

M Islander

New member
I have a 1979 Catalina 350 with Marine power 350's. On start up of the starboard motor there is a gush of green coolant then white in the exhaust water and continues to lose collant when running. Motor starts and runs well.
Water pump impeller is fine,all cylinders pressure test well, heat exchanger tubes are clear and the heat exchanger pressure test is good. Would checking the riser,exhaust manifold gaskets be the next step or should I be looking elsewhere?
 
I would hook the hoses back up and pressure test it again, once its filled up...I would suspect one of the exhaust elbow joints/gaskets not sealing well...

Sometimes, a stethscope can help find the leak when the cooling system has pressure...
 
will do thanks for your help. I suspected the heat exchanger as the one on the port engine has been replaced or rebuilt by the previous owner.
 
So I wud guess the boat is new to you?

The exhaust elbows are normal maintenance items...five years is about it...will vary based on the casting, how much use occurs, and the water quality the boat is in..
 
Ok didnt know that. I called the previous owner and he did not so thats likely the problem. Boats always been in fresh water.
It looks like it might be a big job to remove the elbows I think I will seek some professional help. Thank you for your help.
I'm glad I found this site.
 
On the elbows, the raw cooling water exits into the elbows and gets mixed with the exhaust gases to cool them down...the problem is those gasses are very corrosive...so the cast iron starts to rust then rot...once it starts, you really cant stop it.

When they clog up, they usually restrict to raw water enough that the coolant cant remove enough heat and the engine temperature rises...

there should be a block off plate (typically stainless) sandwiched between two gaskets separating the coolant in the exhaust manifold from the raw water going into the elbow...the risers, if used, could be in either 'side' - I can't say I remember how marine power did it back in that timeframe...

I doubt the elbow rusting up and clogging is the root cause in your case...probably something in the gasket/blockoof plate sandwich...
 
I dont think there is an actual separate riser. Looks like what would be the riser and elbow are one piece. I might tackle it on the port side of the engine as acess is very easy
 
If you do decide to pull the elbow, make sure you drain the coolant out of the exhaust manifold...before any eblow hardware gets loosened...
 
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