Coolant being replaced by sea water?

[RCAnderson]

Re: Coolant being replaced by sea water?

I will take a stab at this one. I think you have a failed heat exchanger. I think that one or more of the tubes that the raw water flows through have ruptured. On my setup anway, the heat exchanger is on the suction side of the engine circulation pump, therefore, there is a bit of vacuum being produced. Couple that with a brand new impeller in your lower end which is providing pressure to the raw water side of your heat exchanger, and you will start to draw raw water into the freshwater side. If you pressure test your heat exchanger this would show up. Those copper tubes inside the heat exchanger will get pretty thin over time, and the extra pressure from a new impeller coupled with a slight blockage from a barnacle or whatever may have been enough to rupture a tube. I believe if you take off the endcaps on the exchanger you will probably see some restrictions in there.
My .02

Ryan

 

[hamishmcduff]

Re: Coolant being replaced by sea water?

The boat is quite old and the engine was replaced 8 years ago.
I purchased the vessel 5 years ago.
As far as I know it retained the original H/E.
I will get some pics posted tomorrow and I will get ready to pressure test the H/E

 

[kilowatts]

Re: Coolant being replaced by sea water?

Hi Guys:

I have the same San Juan setup on all my MCM 165 engines. In my opinion you have a faulty heat exchanger. I see no alternative to taking it off, pulling it apart and testing it! I would think it unlikely that the actual copper tubes have corroded, more likely the top and bottom seal have had it. They produced 2 kinds for this model so contact San Juan and ask for new gaskets, they're very helpful. Good Luck:

kilowatts

 

[hamishmcduff]

Re: Coolant being replaced by sea water?

I've opened the top and it looks as if the top seal is just there to isolate and maybe direct flow.
But it appeared to be passing fluid from the inside past the seal, there appears to be the tell tale signs of green copper residue on the outside of the h/e.
Not alot but there shouldn't be any.
The rubber seal looks in bad shape as it is cracking on the outer edges, I will replace them and test.
I also found a handy test procedure for the impellors volumetric flow in the "adults only" section.
I'll see how well that impellor moves the water too.

 

[hamishmcduff]

Re: Coolant being replaced by sea water?

I applied some city tap water to the H/E today, not alot of pressure but enough to see the results.
Water was spraying out the top gasket and passing through to the closed coolant/engine side.
I'd say the exchanger is definitely gone.

 

[kilowatts]

Re: Coolant being replaced by sea water?

Hi Guys:

Hamish, do you mean the gasket is shot or the copper tubes? For gaskets I've always used 1/8th inch neoprene sheet as does San Juan. If it's the rubber cap type of end, then you need anew cap.

kilowatts

 

[hamishmcduff]

Re: Coolant being replaced by sea water?

BOTH
The gaskets are old and cracked.
I applied some water+pressure to the raw water side and plugged the outlet/return and it started to come out of the closed side of the H/E.
So it appears asthough it has been passing through the copper tubes to the other side, where as far as I know is not supposed to be.
I will post some pics later.