Yes- this started with limited water from the exhaust and overheating. I realize I have two separate water circulation paths. I have had the heat exchanger cleaned and pressure tested, checked the muffler and intake path. Last reasonable possibility is the water pump. I know that the existing pump is pumping water when there is no resistance and that worries me. My concern is what happens if I install a new water pump (in progress) and it doesn't fix the problem. I have made too many errors in diagnosing the problem so far to be confident in where the problem lies and I am also worry about multiple simultaneous system failures. So if the thermostat failed or the fresh water pump failed, I would get overheating. That would not explain sense of limited water from the exhaust, but that might not be the real problem and difficult to measure. I am just trying to think about every aspect of the system. Dave
David Knecht S/V Aries 1990 C&C 34+ New London, CT  > On Jul 24, 2025, at 8:31 AM, Rick Brass via CnC-List <cnc-list@cnc-list.com> > wrote: > > David; > > IIRC correctly this string started with an overheating problem? > > The water coming out of the exhaust is raw water. That side of the cooling > system general has only the through hull, the water strainer, the heat > exchanger, and the exhaust elbow; all connected by various hoses. > > I believe you have addressed everything except the heat exchanger. Have you > cleaned out the tubes in the heat exchanger? If you sail in salt water they > get deposits over time. For my 36hp Westerbeke that is a routine maintenance > item every two or three years. For my engine the cleaning tool is a bronze > brush intended for the barrel of a .22 rifle that I bought at a sporting > goods store. > > The fresh water side of your engine (which actually cools the engine) has the > thermostat, if it has one, the heat exchanger takes the place of the radiator > in your car. The fresh water side of the system is just like your car > engine. My engine has a coolant recovery tank - which makes monitoring the > level of the coolant easy. Not all engines have one. > > If you have addressed everything in the raw water side of the problem and it > still overheats, it may be time to look at the freshwater side of the engine. > > Rick Brass > Imzadi. 38mkll > La Belle Aurora 25 mkll > Washington, NC > > > Sent from my iPad > >> On Jul 23, 2025, at 7:02 PM, Jonathan Tebbens via CnC-List >> <cnc-list@cnc-list.com> wrote: >> >> >> https://www.westerbeke.com/parts%20manual/200144_m4-30_parts_man.pdf >> Pg 31-32? >> >> Jon Tebbens >> >> '78 Mega 30 >> Katherine >> >> On Wed, Jul 23, 2025 at 5:13 PM David Knecht via CnC-List >> <cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com>> wrote: >>> I am in the process of installing a new water pump to see if it fixes my >>> engine overheat problem. I still think the main problem is not enough >>> water coming out of the exhaust so keying on the water pump. But something >>> occurred to me today while working on it that I had not thought of before. >>> Is there a thermostat somewhere in the engine (Universal M4-30)? Can those >>> malfunction? I presume if it did not open, the engine would overheat? I >>> don't even know where the thermostat is so have never looked at it but I am >>> concerned whether that is something I need to check. Dave >>> >>> David Knecht >>> S/V Aries >>> 1990 C&C 34+ >>> New London, CT >>> >>> <pastedGraphic.tiff> >>> >>> Your contributions help pay the fees associated with this list and help to >>> keep it active. Please help by making a small contribution using PayPal >>> at: https://www.paypal.com/paypalme/stumurray All contributions are >>> greatly appreciated. >> Your contributions help pay the fees associated with this list and help to >> keep it active. Please help by making a small contribution using PayPal at: >> https://www.paypal.com/paypalme/stumurray All contributions are greatly >> appreciated. > Your contributions help pay the fees associated with this list and help to > keep it active. Please help by making a small contribution using PayPal at: > https://www.paypal.com/paypalme/stumurray All contributions are greatly > appreciated.
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