Steps to open and check copper tubes on heat exchanger for Universal M25-XPB engine?

Apr 6, 2013
160
Catalina 310 Annapolis
Researching this online, I have not found a step-by-step guide for checking and cleaning the copper tubes in the heat exchanger on the Universal M25-XPB engine in my Catalina 310. I ran Barnacle Buster through it at the end of last season but I would like to be able to see the tubes. I understand I need to drain the coolant and that there is supposed to be a coolant drain somewhere, but I don't know where that is and I've seen conflicting information online. Has anyone serviced their heat exchanger and, if so, could you please walk me through the steps. Thanks in advance!
 
Mar 6, 2008
1,261
Catalina 1999 C36 MKII #1787 Coyote Point Marina, CA.
On my M35B Universal, the antifreeze drain is a plug on the engine block on the port side. Look on your manual for your engine. Save and measure the amount of fluid required to refill.
Disconnect hoses from heat exchanger and remove the heat exchanger. Remove the end caps. I used pipe cleaner brush to clean the tubes.
Replace the zinc and new endcap rubber gaskets.
Reinstall and refill the antifreeze.
Run the engine and watch the engine temperature as air may be trapped in the engine block.
Turn off the engine and loosen and remove the high temperature alarm sensor on the top of the engine and use srynge to add more antifreeze until it starts to pour out. Reinstall the sensor. Run the engine and monitor the temperature.
Done.
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Jun 21, 2004
2,683
Beneteau 343 Slidell, LA
I used a brass gun cleaning brush and rod (22 caliber diameter) to thoroughly clean the tubes. The heat exchanger core / insert was removed from the housing to ensure that none of the debris entered the cooling system.