Universal M25XP Mystery Sounds

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stevetrapani
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Joined: 8/6/22
Posts: 2
Universal M25XP Mystery Sounds

I have a 1987 Mk 1 with a Universal M25XP. Coming back from Catalina last weekend I noticed a tick tick tick sound coming from the motor. Temperature was 150 (normal reading for this particular motor). Water was still coming from exhaust and there was a grey/white smoke coming from the exhaust. I did notice a "hot engine" smell, but dismissed it as the burning off of some coolant from a small leak coming from the thermostat housing.

The speed of the tick tick went up and down with the rpm. At a lower rpm it went away briefly, but came back when I throttled back up. After a couple of minutes more, the engine stopped and I could not restart. I called BoatUS and was towed about 7 miles back to my slip in Long Beach. Back at the dock I tried to restart and it fired up, but was still making noise, so I quickly shut it back down.

Yesterday morning I tried to restart the motor, but it was acting like the starter battery was discharged, however the voltage was normal. I came back with an automotive battery charger/jump starter and tried again. I was finally able to get it going again and this was the result. 

https://youtu.be/-5AEfnyey_s?si=_KSO3PtXayHHzV_y

You can hear the noise and see the grey/white smoke in the exhaust. At the end of the video there is a chirping sound in addition to the tick tick tick before the motor shuts down again, 

I've checked the thermostat, and it opens normally when tested in a hot pot of water. I tested the resistance of the temperature sender and it was higher than it should be for ambient temp (145 ohms). I don't believe the alternator/water pump belt is source of the chirping, because I was listening directly over the engine when it happened and the noise didn't seem to be coming from the belt. There is no water in the oil, but I noticed a little tiny black sooty dust on my finger when I dipped it into the coolant. I checked the operation of the alternator while it was running and it appeared to be be operating normally.

I know the sound isn't good, but it doesn't seem like the motor would run at all if it were a major catastrophic engine failure - pistons, blown valves, main bearings.

Any ideas? Thanks in advance for any suggestions.
Steve

stevetrapani
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Joined: 8/6/22
Posts: 2

Update: I disconnected the alternator/water pump belt and started the motor. Although it did start faster than yesterday, the chirping sound was still present. Shut it down immediately when the chirp appeared.

Without the belt attached, the water pump spins freely. The crank shaft spins as well, but I think I can detect something inside sort of clanking. I suspect that a main bearing, or a connecting rod is making the chirping sound? I fear a major overhaul/replacement is in my future.

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Haro
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Joined: 11/7/14
Posts: 420

How about the raw water pump? Remove the pump and see if the "fork" that is on the engine is in good shape. Raw water is pouring out so it must be OK, but it may be worth a check.

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