Catalina 350 International Association

I recently had an engine overheating problem. I noticed the temperture guage was pegged, and no alarm had gone off, so I want to test the temperature sensor and alarm circuit. Any suggestions on how to go about this?

Alternatively, I am considering installing a backup temperature alarm system independent of the Catalina buzzer, that is almost always inaudible, with an alarm that can wake the dead. Any suggestions on how I might do that?

After anchoring and towing in, the problem appeared to be a failed raw water pump, although the Oberdorfer impeller did not appear to be damaged. The engine got hot enough to boil the coolant out of the system into the pan under the engine, but does not seem to be damaged. The engine starts and runs fine with a new raw water pump.We eventually motor sailed at about 2200 RPM back to our marina for about 8 hours with no overheating or other effects. Any thoughts on other things I may want to check for potential damage?

Thanks

The switch is if I recall from memory, a normally open circuit and when overheated it grounds the path of 12V -> LED -> buzzer -> switch -> gnd. If the LED and buzzer are individually ok (check with a 12v battery and a + and -wire to either side of the LED and buzzer when disconnected) and then if the wiring checks as good with an ohmmeter then the switch by elimination must be the problem. I had a similar issue and used this methodology to find that the buzzer which is essentially two buzzers in one three terminal block (+1 temp +2 oil pressure and -ve/gnd rtn) had failed on the overtemp side and so when I had a problem when motoring out to go sailing, I just got an illuminated overtemp LED and also from the other sensor a pegged temp gauge. I fortunately noticed this fairly quickly, killed the engine and sailed a bit then it worked OK on restarting after it cooled down.. I checked everything afterwards, it had only briefly overheated, no loss of coolant, no signs of any change. I read that if an overheat is severe it does lead to permanent damage immediately and it normally shows as increased oil consumption or heavy smoke (damaged rings) or loss of power and weeping/leakage around the cylinder head due to head warping. You probably dodged a bullet.

I couldn't work out exactly what had happened, I always check at the dock to ensure water coming out on initially starting, so it was working, there was no damage to the raw water impeller or housing. I checked the thermostat a few times in a saucepan of boiling water to ensure it was working, no problems. My best guess was that I sucked a plastic bag or similar junk across the engine thru hull that fell away when the engine was turned off and sailing.

Checked the inlet strainer, changed the oil, changed the thermostat, changed the impeller and fitted a new buzzer and cleaned all the connections and also changed the horrible connector strip ($12 at Catalina Direct, they also stock the buzzer). At the same time I changed the worn engine panel (new enameled metal plate bought from someone who made replacements on this forum), the whole job was very time consuming, maybe 10 hours.
In summary a weird mystery. Anyhow, I toyed with the idea of fitting a bluetooth engine temperature monitor there are lots of them on the internet, but just accepted after 20 years minor gremlins happen and there are two indications of temp provided so its sort of redundant already.

I finally had some time to do some testing as to why the temperature alarm did not work. I found the wire to the temperature switch had fallen off the connection at the thermostat and was behind the alternator. I have no idea how long it has been disconnected, but now I have a new item to check each time we use the boat. I jumped the wire to ground and the buzzer was clear and loud. I don't know at what temperature the switch should be activated, or have any idea of how to test the switch itself. I will say the connection to the switch is a poor design. It is simply a slide on connector rather than a ring connector with a nut (like the temperature guage sensor). It could be prone to falling off due to vibration.