Water flange on Universal M25XP corroded and leaked coolant

[ragtime_c34]

Hi! Long time lurker here, but I've got a problem that I haven't been able to find the answer to through searching.

I have a universal M25XP powering my 1989 Catalina 34. I have recently taken her from Seattle up the British Columbia coast to Desolation Sound and back down to the San Juan islands and have had two issues with overheating on the trip, issues that I wonder if might be indicative of a single root cause. I need some help figuring out that root cause.

1. When I was traveling north, just after leaving Point Roberts and about to cross into Canadian waters the engine overheated the first time. The fresh water pump had seized and the v-belt had melted on the edge of the frozen pulley and snapped. With spares for both the pump and the v-belt on board, as well as enough extra coolant, after an hour or two of tacking back and forth against the northerlies we were back under engine power. Things seemed to be working great, so I chalked it up to just an old pump.

Next 3 weeks: I checked the coolant every few days. It had gone down some, which I chalked up to air pockets getting worked out.

4th week: Coolant level much lower than expected, had to add distilled water to fill up since no more coolant on board. Checked daily for leaks, couldn't find any. Coolant in the bilge so it's coming from somewhere. Bypassed the water heater circuit to rule out a leak along those lines.

2. Back in the San Juan islands now, leaving Stuart Island on my way to Friday Harbor it overheats a second time. Now there is a hole in the water flange, the part that houses the thermostat, that looks like the engine was shot (see picture). We sailed to Jones Island to pick up a mooring for the night, then on to Friday Harbor the next day and dropped anchor. I've been there about a week now waiting for the replacement water flange to arrive.

The corrosion of the water flange definitely indicates to me something wrong and I'm looking for suggestions on how to troubleshoot that problem. Voltage electrolysis as described here: Diesel Engine Electrolysis: Why They Are More Prone To Damage seems like a candidate, but I can't find anyone talking about this for marine engines or in these forums… is this an issue for boats?

Additional electrical and cooling system data that might be relevant:
1. Boat is new to me as of January 2017, I have only guesses about the state and maintenance of her before then.
2. Replaced leaking raw water pump in September 2017.
3. Replaced a faulty voltage regulator with a Balmar MC-614 in April 2018, alternator was non-functioning for about 8 months before this due to bad voltage regulator. (maybe I did something wrong here?)
4. I flushed the coolant system in June 2018: emptied coolant, cleaned heat exchanger with rydlyme, re-painted hx, replaced zinc in hx, replaced hoses, put in fresh coolant 50/50 ethylene glycol from an auto parts store
5. Added solar panels in July 2018. (maybe screwed this up… but it seems like a pretty simple process)

This ended up being a bit more than I meant, so thanks for reading this far! I think my questions can be boiled down to these two:

1. Has anyone seemed something similar and can explain what happened to them?
2. Does the troubleshooting route in the link I gave above seem like the correct route forward or are there other paths to follow?

Thanks!

-tony
s/v Ragtime

[DougR]

It's about impossible to say what the cause of the problem is without a lot of experience with that particular engine, and perhaps seeing the same problem several times. That said, problems like this can frequently be the result of many years of cooling system neglect, specifically the failure to maintain the anti corrosion levels of the coolant. One of the most important properties of " antifreeze" is really anti corrosion. The additives within the coolant coat and protect the inner components of the cooling system and protect against cavitation of the cylinder liners, cavitation of the water pump housings and impeller, and help protect against velocity erosion of internal surfaces. These additives become exhausted over time and need to be recharged, or the coolant needs to be replaced. On small engines like this coolant replacement is the normal course of action.

The fact that the circ pump also failed/seized might indicate that all isn't well within the coolant system, and a more in depth examination of the system might be warranted.

DougR

[donradcliffe]

Do you now think that the coolant in the bilge was coming from the hole in the wter flange??

"Marine" diesels tend to be assembled from a bunch of incompatible materials like iron and aluminum, so it is not unheard of for older engines to have corrosion or erosion issues. I'd replace the damaged part and drive on.

If you are concerned about voltage electrolysis, take a good multimeter and measure the voltage between the various parts of your engine and the common ground point. Anything over 100 mv would bear investigating further and anything over 700 mv would be cause for concern.

[ragtime_c34]

Originally Posted by donradcliffe

Do you now think that the coolant in the bilge was coming from the hole in the wter flange??

Yeah, my theory is that it was seeping out of a crack in the water flange as steam and condensing different places in the engine compartment then dripping down into the bilge. That would explain why I couldn’t find a source for the leak, seemed like it was all over. Eventually the crack blew out to what’s in the picture, then it was easy to spot.

I guess I won’t know if that was the case until I have her running again though.

Thanks to both of you for responses!

[Jd1]

Originally Posted by ragtime_c34

Yeah, my theory is that it was seeping out of a crack in the water flange as steam and condensing different places in the engine compartment then dripping down into the bilge. That would explain why I couldn’t find a source for the leak, seemed like it was all over. Eventually the crack blew out to what’s in the picture, then it was easy to spot.

I guess I won’t know if that was the case until I have her running again though.

Thanks to both of you for responses!

You wouldn't get coolant in the bilge from steam escaping and condensing, that only gets you water. If you did get coolant in the bilge prior to the hole opening up than you have another leak someplace. Could be as simple as a hard (old) hose which I experienced. Took me quite a while to find the issue too.

[Stu Jackson]

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