I normally see 175 +/- but now 195 at 80% throttle. Not down on power, but some small wisps of whitish-gray smoke. Exhaust water quantity output by the eye looks to be about normal. Can this be anything other than the heat exchanger starting to go?
Universal M-12 running hot
- Thread starter odaydokay
- Start date
Sorry I don't speak Universal language, only Yanmar.
Even in my wildest dreams, all I can come up with is the stat is jammed in the closed position (<1% probability). It's easy but unlikely. If the raw water discharge is the same, can't see anything else other than a dirty H.E.
I know you've already checked everything else on the antifreeze side.
Maybe a tad of antifreeze loss but not much. I think maybe next I pull the HE anode and see if sea water only or some coolant comes out. The last time this happened was 7 years ago, almost the same temp situation and a new HE cured it, but I don't want to jump to that conclusion without eliminating some other possibilities.
I would disconnect the raw water hose at the exhaust elbow and examine the flow there. On my heat exchanger I can see the coolant input flow with the fill port cover removed, maybe yours is similar. If those are good you could check to see if your bottom and/or prop are fouled causing an excessive load on your engine.
I’d start by opening the heat exchanger and looking for debris. Even if the water flow looks good there could be seaweed in there reducing the cooling. Also check the impeller to make sure it still has all its vanes.
Good ideas. Thanks. Yes, I should not assume I can judge exactly whether I am getting the right amount of water flow. I have an external "South Bay" strainer (cheese wedge type with perforations) and it had barnacles on it, but scraping them off did not help. I will start by pulling the cover off the water pump to check the impeller condition. As for the HE, I need to get two end 2" cap gaskets before I pull those both off and I have not yet found where for those. I think seaweed is unlikely, but anode residue and impeller pieces are not out of the question. Anyone know the "do not exceed" operating temp on these engines. 200 already makes me uncomfortable, but maybe I am being too conservative.
Interesting! Did not know one could pull the HE cap off with engine running! The load check also makes sense. Thank you.
I don't think you can. Maybe the poster was talking about the coolant filler cap on the exhaust manifold?
The manual says 165 to 195.
Many appear available on an internet search but maybe not for pick-up in your area.
My guess might be your problem comes from a slow accumulation of growth inside the HX tubes. The volume of raw water might not be noticeably reduced but the ability to exchange heat could be compromised. I had similar symptoms that particularly showed up as the sea water temperature increased in the summer. I soaked my HX for a while in a mild acid solution then gently cleaned out the tubes with a wooden dowel and it helped a lot.
That makes sense. After only 7 years of light use, I am hoping the HE is only clogged like you say and not perforated. I did an OE heat exchanger one time ($$$$$!) and went to the Mr. Cool this time, so would be disappointed if perforated so soon. First step is to look at the pump impeller, then on to the HE. Much appreciate the time you took to weigh in. Yes, I know the 195 part but that is not stated as max. Still at 200, I back off, even though I have since read 220 as max.
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Well, I'm sure you are all waiting with baited breath for my further findings 
I started by pulling off the intake line to the water pump, just to be sure there was good water there at least. On this boat you can do that without a flood as the water level is about 4-6 inches below the pump. I stuck a snap style bottle stopper in there (perfect fit). Pulled the cover off the Oberdorfer to check for broken vanes. All perfect, like new, but the last 1/2" or so on that intake line had a split in the rubber casing, so I shortened it to get a clean connection. Started the engine but did not see a water flow change as far as I could tell and the engine got warm pretty fast so shut down and attacked the HE. I reasoned that since no impeller junk would be found at the input end, it made best sense to start at the output end; heck it's 95 out so I wanted to move things along here. The other end of the HE was not pretty and the same thing another of our owners described: Pieces of anode and residues and in my case also about half of a complete anode!!! Unscrewed the working anode, checked it (looked good and no coolant came out, so no internal damage most likely) and left it out to use the area as a drain hole and flushed the end area with a very slippery detergent my company sells. Replaced the anode, closed everything up and fired up the engine. Immediate difference in water flow and engine tone (not to mention a pant load of suds!). The engine noise changed also, less "gargle-putt-putt" and a softer water gushing sound. Am I done? Jury still out as I could not take a full run and can't for a couple more weeks, but things are certainly not going to be worse and I am guessing better to ok when the run comes. I do think an HE ream and vinegar saturation, let stand and flush, etc. would make sense and I will put a new impeller in soon. A couple of observations: I recall the OE heat Exchanger had a cap at only the intake end. The unit I have (Mr. Cool brand nickel-copper model) has caps at both ends, a huge plus, no? The other thing is the pump impeller. About half the vanes as the Sherwood I had before, so if you lose a couple I am guessing you are going to pump less water than if two are gone from a Sherwood. You guys helped me a lot on this one so I hope this report pays forward to someone else. In a couple weeks I will try to come back with my new running temp numbers.
I started by pulling off the intake line to the water pump, just to be sure there was good water there at least. On this boat you can do that without a flood as the water level is about 4-6 inches below the pump. I stuck a snap style bottle stopper in there (perfect fit). Pulled the cover off the Oberdorfer to check for broken vanes. All perfect, like new, but the last 1/2" or so on that intake line had a split in the rubber casing, so I shortened it to get a clean connection. Started the engine but did not see a water flow change as far as I could tell and the engine got warm pretty fast so shut down and attacked the HE. I reasoned that since no impeller junk would be found at the input end, it made best sense to start at the output end; heck it's 95 out so I wanted to move things along here. The other end of the HE was not pretty and the same thing another of our owners described: Pieces of anode and residues and in my case also about half of a complete anode!!! Unscrewed the working anode, checked it (looked good and no coolant came out, so no internal damage most likely) and left it out to use the area as a drain hole and flushed the end area with a very slippery detergent my company sells. Replaced the anode, closed everything up and fired up the engine. Immediate difference in water flow and engine tone (not to mention a pant load of suds!). The engine noise changed also, less "gargle-putt-putt" and a softer water gushing sound. Am I done? Jury still out as I could not take a full run and can't for a couple more weeks, but things are certainly not going to be worse and I am guessing better to ok when the run comes. I do think an HE ream and vinegar saturation, let stand and flush, etc. would make sense and I will put a new impeller in soon. A couple of observations: I recall the OE heat Exchanger had a cap at only the intake end. The unit I have (Mr. Cool brand nickel-copper model) has caps at both ends, a huge plus, no? The other thing is the pump impeller. About half the vanes as the Sherwood I had before, so if you lose a couple I am guessing you are going to pump less water than if two are gone from a Sherwood. You guys helped me a lot on this one so I hope this report pays forward to someone else. In a couple weeks I will try to come back with my new running temp numbers.
Thanks for the update. My HX has an end cap on only one side. Would certainly be easier to clean out if it could be opened from both sides ( the anode is on the end that doesn't open so if bits break off it is very difficult to get them out ).
).Absolutely, Richard. Impeller junk will be available to clean at the intake end, but with no cap at the output end, you cannot do too much about anode and other residues there, a design error in my view, now that I have had the Mr. Cool version. I meant also to talk about something else I saw, that being that at both end caps, but much more at the output end, I noted dried salt water residues suggesting that some seepage had occurred around the cap ends. Makes me think that when there is some obstruction, the HE heats up, an overpressure maybe occurs and the end cap seals start to seep or they just deform from the heat. Just theory on my part, but I think pulling off the caps and inspecting, cleaning out/flushing and replacing the seals is not a bad maintenance exercise. Every year maybe not, but maybe tie in with the impeller replacement every 2-4 years depending upon motor hours elapsed.Thanks for the update. My HX has an end cap on only one side. Would certainly be easier to clean out if it could be opened from both sides ( the anode is on the end that doesn't open so if bits break off it is very difficult to get them out
See my full report, but I tried to actually do what you suggested (and thank you, by the way!) On my set up the manifold leads to a pipe (1-1/2" NPT I think) with no mixing elbow, but rather a "wye" where the water is injected a foot +/- above the Vetus water muffler. Two clamps hold the hose for the wye. I got the clamps off easily but the rubber hose would not budge and using a lot of force was going to either destroy the hose or break the wye coupling, so I went on to the heat exchanger which brought the results I reported. Since I saw a water flow improvement, my sense is there is not much obstruction there, but I will keep this location in mind as one that may need to checked and reamed.
Sooo.....I got out again yesterday. It took 25 minutes but I hit around 200 again before good wind and then shutdown for sailing. No wisps of smoke at all, though. The temp made me wonder if I accomplished much with the junk I removed from the end of the HX (see previous posts). This morning I recalled I had not looked at the coolant level for a while and added maybe 2-3 oz. On the way back we had to motor a good half hour and she did not go over 180. That coolant addition or some more junk got flushed out through the system? Who knows?
Sounds like youre winning!
Hopefully I will soon- I was about to start a new thread on a similar issue with my M18. I assume it's down to zinc fragments in the HE...
I dont have a hot engine, but I did have a weeping oberdorfer which i was delighted to finally fix with a new shaft and impeller,.. only to find to my horror that despite pumping strongly, suddenly no water at all was coming out the exhaust! I opened the HE (single ended, as with yours, annode at closed end) - drained into a pot and saw quite a lot of grainy debris. Replaced the cap and now water is coming out the exhaust. Ive not removed the anode but its safe to say that I didnt get all the crap out the HE. Dont know whether to replace with a Mr Cool just in case or to find some better method of flushing?
I'm also curious about the intention of the anode fragments. Are they designed to desintergate and head out the exhaust? Seems crazy to have the anode at the closed end but i wonder if that is fine provided they disolve and are expelled with strong pump pressure?
Hopefully I will soon- I was about to start a new thread on a similar issue with my M18. I assume it's down to zinc fragments in the HE...
I dont have a hot engine, but I did have a weeping oberdorfer which i was delighted to finally fix with a new shaft and impeller,.. only to find to my horror that despite pumping strongly, suddenly no water at all was coming out the exhaust! I opened the HE (single ended, as with yours, annode at closed end) - drained into a pot and saw quite a lot of grainy debris. Replaced the cap and now water is coming out the exhaust. Ive not removed the anode but its safe to say that I didnt get all the crap out the HE. Dont know whether to replace with a Mr Cool just in case or to find some better method of flushing?
I'm also curious about the intention of the anode fragments. Are they designed to desintergate and head out the exhaust? Seems crazy to have the anode at the closed end but i wonder if that is fine provided they disolve and are expelled with strong pump pressure?
The most common reason for overheating is a plugged-up heat exchanger. I have had to remove mine for cleaning twice in the 24 years I have owned my C30. It is not hard to clean. Any Phosphoric acid (Barnicle buster) will do most of the work. I then finished it off with a 12" long x 3/16" drill bit which I used as a hand reamer to make sure that each tube was clean and open. Just twist it with finger pressure on the bit. Using it in a drill could damage the tubes.
If you have the money a new Mr Cool is an option but I haven't had to do that.
You can get most of the broken pieces out by removing the HX and the anode and then just shaking them out of the fitting the anode goes in. It helps if you can have some water flowing through so I hooked up a garden hose to the HX to get that happening. Also helps if you put a thin stiff wire into the fitting and jiggle that around in there while the water is flowing through. Kind of like trying to get your coins out of an old piggy bank that didn't have a removable plug if you ever did that as a kid.
A trick I learned from a mechanic is to cut the new anode down by 3/4 inch or so before installing. It seems then that the anode wears more evenly rather than at the bottom end so it doesn't just break off. Better still, just replace the anode more often so you get it before it breaks off.