For those who were interested in the inquiry re: installing a larger heat exchanger on a M-35 for a 1992 C36, here is the reply from Westerbeke staff:
[I]Your email to Gerry at Catalina Yachts has been copied to me in his reply to you.
The thermostat in your Universal is rated at 160 F. I generally will hold the engine operating temperature, depending on the temperature of the sea water and engine load, in the 150F - !70F range.
I would for the sake of accuracy. Verify the engine operating temperature with the use of a heat gun monitoring engine temperature at the thermostat housing where the instrument panel’s temperature gauge sender is located. There can be a number of degrees of inaccuracy from gauge to gauge and sender to sender.
Diesel engines with a closed antifreeze cooling system operating in the 180F range is by no means detrimental to the engine. Your engine operating in shallow warmer water than found in the Chesapeake has caused the increase in operating temperature you are seeing with your engine.
Like a cars radiator increasing its size or that of the heat exchanger does provide for more cooling area and helps the engine thermostat to better control engine operating temperature at the rating it has.
[COLOR="Red"]Larger size heat exchangers for the Universal M35AC are not available and as mentioned above. The operating temperature of the engine in the 180 degree range is not detrimental to the engine.[/COLOR]
Very Best Regards,
National / International