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Antifreeze air lock?


May 28, 2013
Catalina C310 SF Bay/Delta
On my Catalina 30 with M25 engine when drain and replace antifreeze sometimes would have air lock blocking circulation with
result overheat. Solution would be to slightly open "knob on thermostat and " burp" eng. Idle to full throttle then back to idle
two three times. Will drain and replace antifreeze soon ( 500 hours) and wonder if have same problem with XPB eng?
First time will be doing this on this eng. Thanks for any replies.

Nov 18, 2010
Catalina 310 Hingham, MA
Yes. If you look at Mainesail's contribution to the C34 wiki (Stu's link), reply #14 it shows a better way to do it.

I just did mine for probably the 6th time since owning the boat two days ago. Since the 2nd time I have been doing the Mainesail system and have never had an issue.

In this pic you can see the improved vent. Because of the clearance on the steps I had to turn it side ways instead of up.

Good luck and fair winds,