Fixing engine that overheated during Penobscot Bay cruise
- Thread starter dhill
- Start date
Prairie Schooner
Jeff & Donna, E35-3 purchased 7/21
Really nicely done Dave. I like how you highlighted the parts you were talking about. Did you do that on a separate image and do a fade transition? Very effective.
Your results raise a question for me. Can an engine run TOO cool? Does it need a certain temperature to run efficiently?
Your results raise a question for me. Can an engine run TOO cool? Does it need a certain temperature to run efficiently?
dhill
Member III
Thanks @Prairie Schooner !
Yes, they are separate images and I did a fade transition. I'm glad you like that.
When I couldn't get the temperature to rise after replacing the heat exchanger, I did worry about the engine running too cool, and found articles saying it can lead to sludge buildup in the engine and increased fuel consumption (see https://industrial-radiator.com/diesel-engine-equipment-in-cold-operating-temperatures/#:~:text=Overcooling can cause sludge formation,valve lifters and valve stems. and https://eeuroparts.com/blog/engine-running-cold-waiting-can-damaging/). Our marina docks are reaching end of life, and the finger of the slip I rented in 2021 was on its last legs, so I hesitated to put the engine in gear and raise the RPMs. Running the engine in neutral at higher RPMs was not really sufficient to raise the temperature, at least in the time I was willing to wait. So the real test came when I actually went for a sail, and when I did that, I found that running the engine at 2100 in forward (about 6-6.5 knots) raised the temperature to 160°F and kept it there. The thermostat closes completely at 165°F, according to my service manual, so I think that temperature is good. I think that is also in line with other temperatures I've seen on this forum and elsewhere for Universal M25 and M25XP diesels. When I ran it at 2300 to 2400 this past summer, it went a little higher, perhaps to 170°F. With the old 2-inch heat exchanger, even before it leaked, I was only able to run the diesel at about 1800 rpms for long periods of time without the temperature raising about 180°F, so I'm pretty happy with the change. Generally, I think that 160°F to 180°F is the sweet spot, although I'm happy to be corrected if not.
Hope that helps!
Dave
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dhill
Member III
Thanks @Kenneth K !
I have not read about the potential problem with my setup and would definitely like to find out more. I do get quite a bit of belt dust, so I think I may have some alignment problems, which I'll check out further this spring. If you can point me to any information on my alternator bracket, that would great!
Thanks!
Dave
From MaineSail's website: https://www.pbase.com/mainecruising/universal_alternator_bracket
My blog post regarding the topic: https://ericsonyachts.org/ie/ubs/ma...placement-exhaust-riser-rebuild-and-more.539/
Good luck.
Pete the Cat
Sustaining Member
I was able to get rid of the belt dust very easily--surprised me how easily. Just put some washers behind the bracket bolts here and there and aligned it by eye--a metal ruler helped my eye. Magically stopped all the dust. I had imagined having to bend the bracket and lots of trouble--no such difficulty.
Pete the Cat
Sustaining Member
I would recommend buying a new thermostat (unfortunately, and also recommend getting the exact one for the engine rather than a generic one from the autoparts store as the 25XP seems to have a slightly odd diameter-it is a 160 degree and opens at that temp) and keeping it around until you have occasion to take things apart again--I see no problem that needs immediate attention. I, too, have trouble with the same engine getting the temp up in the slip without a good load. The manual says this engine is meant to run at 160 but, as you note, I would not be concerned if it showed 180--many--maybe most--recreational diesels run at 180 and I think that slightly higher temp is probably marginally better for the engine in the long run. I also would not put much stock in 10 degree differences in the readings as the gauges are notoriously not really accurate. it is also common when you empty and refill the antifreeze to get air pockets in the system that take time to work out; so folks should not be too concerned if the coolant needs to be topped off right after the first fill--probably not leaking, but needs to be checked and topped off. Also, the only reliable way to check coolant levels in any engine is to remove the radiator cap--there are too many variables in the overflow tank to trust the levels in them. My overflow tank on my 32-200 is mounted in the lazerette and is so high relative to the engine that it is useless because anything it it would just run out if you open the radiator cap--not sure what they were thinking. FWIW.
Pete the Cat
Sustaining Member
You should look at Mainesail's piece on the location of the alternator bracket, but I do not see a problem with your set up--though the view is not clear in the video. Seems like the previous owner did some work. on your engine: a KN filter, and a proper sea strainer--those were not standard from the factory, so maybe he already did this change. FWIW.
dhill
Member III
Thanks @Pete the Cat ,
I believe I indeed have the problematic alternator bracket, but I'll have to check some other pictures. The previous owner did do some cool things to the boat, but I put the Groco sea strainer and KN filter on last year.
I am surprised at the cost of the new alternator bracket kit - $578 at Catalina Direct - even for marine stuff! That price seems to be the going rate at other places as well. Perhaps the thing that has saved me from failure is the fact the engine has relatively low hours (about 1,100)?
Threads like this are why I really appreciate this community! I would never have known this was a potential issue.
Thanks to you all!
Dave
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Seems I read that "contributing factors" to the old bracket's failure were higher output alternators, highly discharged batteries, and overtightened belts. Don't upgrade to a higher output alternator until you've replaced the bracket.
That is not like the bracket on my former 1988 M25XP, and looks like the one the old service bulletin said to replace.
Also, the copper elbow that your engine has just above the crank pulley should be used to turn the direction of the hoses right at the edge of the engine casting and route the hose aft. i.e. it's right under the support for the alternator.
Also, the copper elbow that your engine has just above the crank pulley should be used to turn the direction of the hoses right at the edge of the engine casting and route the hose aft. i.e. it's right under the support for the alternator.