Tech Wiki

Overheating Due to Heat Exchanger

My engine is overheating with a 2" heat exchanger. How much is the 3 inch heat exchanger and how difficult is it to change?

Responses:

I bought mine from Torrenson Marine. Found them on the web: http://www.torresen.com/~torresen/universal/welcome.html. I called on the phone; they were fast, helpful and expensive. About $400.00 for the exchanger. It fit right on the same mounts as the old one. It has been flawless. The engine temp has routinely been 160 instead of 185-200. Thomas M. Barba


(Note, apparently, sometimes the bracket does need to be altered:) You will need a piece of 3" steel pipe to reshape the bracket, and that's tough to find. I have a piece if you can arrange a pick up. I took the bracket off the engine to reshape it. Simple job. You might as well change the hoses while you're at it. David, #247


Other diagnoses:

I fought overheating on my 1986 Catalina with 2" heat exchanger for a long Time, like 5 years. I live in NW florida in warm water. I agree that the 2" is marginal (so does Catalina since they switched to the 3".) However, if everything is tip top the 2" will keep up. If you are going above thermostat temp under any conditions, full throttle for example, you have at least a minor problem Start with the sea water system:

  • Check for grass/barnacles in intake and filter, new impellor in sea water pump (old can look good but be stiff and not sealing well), broken impeller blade from an old impeller problem somewhere down stream.
  • Take out heat exchanger and shake it. If it rattles you have old tips of pencil zincs inside. (The dissolve in the middle and the tips stay in there.) They will plug the cores and are a major cause of overheating problems.
  • Take the exchanger to radiator shop and have it boiled out. That may not do it. If you pound and shake long enough you can get them out of the pencil zinc insertion hole.
  • Check for bent or pinched hoses impeding water flow.
  • Check for carbon build-up where the sea water dumps back into the exhaust pipe partially blocking the water flow.
  • On the fresh water side, if you have air in the system, you will get inefficient flow and pump cavitation.
  • Look at the check valve between the overflow tank and the plumbing to the hot water heater. (located in cockpit lazerette) This valve is not made for antifreeze. I recommend replumbing the rube-goldberg plumbing valve at the rear of the engine used to control amount of heating going to the hot water heater. It is a major source of cavitation and air.
  • Replumb the hot water heater to the thermostat bypass fittings (short hose between the fresh water pump and the thermostat housing, which is the way the new engines are plumbed.)
  • Try a new thermostat. It may be stuck closed. (take it out and see what happens).

Your problem may be one or several of these items each contributing a minor amount of inefficiency. I finally broke down and bought a 3" heat exchanger. You have a lot more margin in the system plus you can take off both ends of the heat exchanger for cleaning out the zinc pieces. I found it very easy to change. You have to fool with the mounting brackets, but that is it. The hose connections are the same. George G.