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Coolant In Exhaust 351W

J

Jgallo17

New member
Hello all,

Recently installed an overhauled Ford 351W into my boat; it's a full freshwater-cooled system. When I connect water via a hose connection, antifreeze is coming out of the exhaust. We have tested the heat exchanger, and there are no leaks internally. To me, the only thing that can be happening is mixing of coolant in the risers. Since this is a fully closed system, we installed block-off plates (60207). There is a vent hole in this plate; not sure if that can be the source of the coolant. Each plate is between a set of 27-99777 gaskets. I'm not sure where else coolant and water have an interface in the system. Any ideas or help are appreciated!
 
I'd like to add that when the engine was run outside of the boat, no coolant was present in the exhaust. Only once we put it in the boat with a hose connection to the water inlet was this problem noticed,
 
Was the engine you pulled out FWC or did you add the FWC when the rebuild was done?

How long did you run it outside of the boat?
 
The boat was FW from the start.

Ran it outside the boat for no more then 3 minutes maybe 3 times or so. Even with the engine not running and just the water hose running coolant is coming out of the exhaust.
 
risers aren't distribution blocks...

how many hoses are connected to the heat exchanger?

I'd suspect you never saw the coolant when the engine was out of the boat because the engine never got hot enough to allow the coolant to circulate...
 
makomark said:
risers aren't distribution blocks...

how many hoses are connected to the heat exchanger?

I'd suspect you never saw the coolant when the engine was out of the boat because the engine never got hot enough to allow the coolant to circulate...
Click to expand...
There are 4 hoses connected to the heat exchanger. Two on top that are the return from the manifolds. And two on the bottom. One is seawater in. Other is coolant out to the water pump.
 
that wont work...need another (or two) for sea water OUT...

That plate, with the weep hole, is for raw water cooled configurations...what I found in the factory manual is that the closed cooling configurations use a distribution block between the exhaust manifold and the elbow...it provides the function that a full block-off plate would as well as providing a hose barb to allow the coolant to return to the heat exchanger...if its an aftermarket system, then things may be significantly different...
 
makomark said:
maybe this will help...from the Mercruiser manual:
Click to expand...
My apologies, my heat exchanger does have 5 connections. Raw water in and out, 2 coolant return lines, and a coolant to water pump line. See attached photo. The far right connections are the raw water.

And noted. That makes sense good to know that vent hole is for raw water systems. That might be my problem….
 
makomark said:
that wont work...need another (or two) for sea water OUT...

That plate, with the weep hole, is for raw water cooled configurations...what I found in the factory manual is that the closed cooling configurations use a distribution block between the exhaust manifold and the elbow...it provides the function that a full block-off plate would as well as providing a hose barb to allow the coolant to return to the heat exchanger...if its an aftermarket system, then things may be significantly different...
Click to expand...
As of right now i have a forward cap on the manifold and on the back of the manifold as well to circulate the coolant through. Part number 1-60252.

 
Don't see any attached photo.

Agreed, the blockoff with weep hole is likely source of coolant entering elbows...

They are probably all you will find...if you know a good welder, they can fill the weep holes pretty easy..

I,d make sure the coolant flows thru the exhaust manifolds from lowest point to highest point...the idea is to ensure minimum opportunity to have an air pocket remain..
 
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