496 MAG HO heating problem
 

I have a pair of 2004 496 MAG HO motors in a Baja. I bought the boat last fall. I installed two new brass water pumps and back flushed the system until all the lines were clean. I installed new thermostats, cleaned and inspected the heat exchanges cores and installed new gaskets/grommets when reintalling the heat exchangers. I have run the boat about 10 hours with no problem....temps have been good....no over heating any more.
Now last Sunday we out on the river and my one of my engines overheated. Upon inspection the gasket/grommet on the non thermo stat end of the heat exchanger had blown out and dumped all of the engine anti freeze in the bottom of the boat. I have replaced the gasket/grommet and run the boat for an hour and everything is OK.
Has any one every seen the heat exchanger gaskets/grommets blow out? I had run the boat at WOT for about 60 seconds just before the gasket/grommet failed.
Any thoughts???

496 if the two clamps that go to te heat exchanger to the crossover are not tight that could happen.

The two clamps appeared to be tight when I took them off. The gasket/grommet was split open and pushed up twards the heat exchanger tank.

When I took the exchanges apart mine looked awful. Cracked and out of shape at 55 hours

It sounds like you may have been a little rough on 'em when you installed the new one. It helps to put a little dielectric grease all over them so they slip into the respective grooves fully etc.

I have seen mine where they "looked" fine but then after looking closer it's tougher to get them properly seated than what I originally thought...

If you grab the seal with a thumb and index finger and squeeze while turning them in the grooves it will help insure they went in all the way...

They are not something you want to rush. They get damaged very easily as you have found out.

Also, over the years and depending on your climate and storage, they do harden and fail.

Your new one probably split due to the seal not being at exactly the right place when the heat exchanger came in for the surface mate. Again, the grease really helps a lot.

Hope that helps you.

I agree with sd fever use grease and tighen the thermostat housing last

Ok thanks guys I will run it and keep an eye on things.
I did install the O-Ring/Grommet dry....Ray at Raylock had mentioned in one of his replys that is how they do it.
My big concern was that I had some high pressure building up in my closed cooling system that poped this o-ring/gasket out.....like a leaking head gasket or something.