Merc 470, 4" heat exchanger end cap corrosion

[bently]

I have upgraded my heat exchanger to a 4" on my 470. After the first outing the temp was perfect and once I got home I took off the end caps and found a white crusty build up on both end caps on the inside. It looks like the end caps are aluminum and have the same manufacturing name on them as the heat exchanger. How do I correct this? I was planning on putting a coat of paint and hardener over the inside surface to create a barrier, would this work?

Thanks

 

[dn010]

Re: Merc 470, 4" heat exchanger end cap corrosion

Did the end caps have full gaskets on them? The caps shouldn't have contact with any cooling water...

If they are corroding under the gaskets, I'm sure you can paint them but you'll probably have to etch them or etc. in order to get some paint to adhere. Mine are brass so I've never dealth with that issue. I'm sure others will chime in.

 

[stonyloam]

Re: Merc 470, 4" heat exchanger end cap corrosion

Yeah dn is correct. Here is the gasket : http://www.mercruiserparts.com/showSpecialPicture.asp?pn=99960 #27-99960. I would think you could clean it up and paint it. Parts illustration for the exchanger: http://www.mercruiserparts.com/Show...64.png&inbr=908&bnbr=120&bdesc=HEAT+EXCHANGER

As a little follow up: those gaskets need to be in good shape because the raw water flows back and forth 3 times: in and front to back in the starboard tubes, back to front in the center tubes and back and out through the port set of tubes. So the gaskets need to be in good shape or else the cooling water could leak into the outlet rather than flowing through the tubes. Could reduce the cooling capacity of the exchanger.

 

[bently]

Re: Merc 470, 4" heat exchanger end cap corrosion

Thanks for the info, I was using a perimeter gasket or similar to a large flat "O" ring. I will order new gaskets.

 

[stonyloam]

Re: Merc 470, 4" heat exchanger end cap corrosion

Here is where they talk about the exchanger in the manual: Boatinfo - Mercruiser Service Manual nr. 8 - 1985-1989 - Mercury Marine 4 Cylinder Engines Now correct me if I am wrong since it has been forever since I have had my caps off, but I believe the starboard rib in the front is solid, and the center/port one is cut out to allow flow from the center tubes into the port set of tubes. Am I correct there? If so, then you need the gasket to seal the top surfaces of the ribs. A close up photo of that front end with the cap off would be great info.

 

[bently]

Re: Merc 470, 4" heat exchanger end cap corrosion

Really good info, I thought the sea water was just going in one end and out the other.

 

[stonyloam]

Re: Merc 470, 4" heat exchanger end cap corrosion

Really good info, I thought the sea water was just going in one end and out the other.

Nope, heat exchangers are more complex then the look. While we are on the subject, in the sealed antifreeze section there are baffles that direct the flow around the tubes for maximum efficiency as it passes through the exchanger.