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Scarce as hen's teeth...

Jan 19, 2010
950
Catalina 34 Casco Bay
Started to notice a gradual overheating taking place with my Universal M25. If I pushed the throttle to 2500rpm the temperature gauge would slowly rise. Tried new impeller(s) without success. So, it became an " only go to 2500 for short periods. The other day I had started the engine and furled in the Genoa and then dropped the main. Only had a short distance to motor. I religiously check temperature gauge. What the (#$*(@.. temp indicated was approaching 180. A look over the transom indicated no water from the exhaust. Made the mooring at about 190 degrees. The the trouble shooting began. A cacophony of issues.. First the pump and impeller had run dry for 10-15 minutes. After things cooled a bit, the impeller was swapped out for a new spare. NO JOY. Decided to check the flow in from the seacock. Closed it, removed the strainer and re-opened.. Just a trickle .. Hmmm. Removed the service plug.. Still a trickle.. Ramrodded a coat hanger down.. Got resistance.. Sawed it back and forth.. Finally got a decent flow. Tried the engine.. No flow.. Removed the raw water feed line. Blew into it.. Eeh, so-so. Tried to and finally sucked salt water.. Primed the pump and re-tried the engine .. Still no water. Got the Admiral to come down the next day. Had her engage the starter while I watched the impeller. Well, the new impeller stayed put while the center hub spun with the shaft....Seriously ? Dropped the exchanger end caps..Clear as a whistle.
....Another impeller is accessed. It spins as it is supposed to. Pump cover goes back on, engine is spun up..NO WATER... Uggh ! I've come to the conclusion that it's one of three possibilities. First, the hoses.. Replaced the intake and pump to exchanger. Both were heavily cracked. Could its be sucking air that is preventing the drafting of water? Engine start time...NO WATER.. But new hoses.. Down to my last 2 possibilities. The cam in the bottom of the pump and the pump itself. Found and ordered CAM. Started looking simultaneously for a new Oberdorfer N202M-15 5 bolt . None, nada, zero, zilch... Oberdorfer decided to move from NY to MI in March.. Because of COVID, production has been on hold. I tried every place thinkable from east coast to west coast, gulf to Canada... SCARCE AS HEN'S TEETH they are... None to be had. Thought I'd found one at a distributor in MA. It was marked up over 150% above the lowest price I found, but as it turned out... NO GOTS...
The CAM arrived last evening. Quick trip to the boat this morning. Swapped out the CAMs, lubed up the impeller, re-sealed the pump and fired the engine..... Wait, what's that sound... a gurgle ... and ... and...and WATER.... Yeah !!!

I have a standing order in place for a new pump. I believe my pump is OEM and after 34 yrs the tolerances have got to be thin. It is interesting to note that the impeller that failed apparently is not an isolated event. So. if you change out an impeller be forearmed that there no guarantees that it will function as needed. The process of spinning over the engine while watching the impeller was a suggestion from a marine service tech who has witnessed many impeller failures in recent years..
 
Jun 25, 2004
288
Hunter 306 Pasadena MD
I'm impressed with your persistence as well. But I'm not sure I understand. Even if the cam was worn down a bit, you'd expect it to still pump some water: just maybe not quite as much. What do you think was going on? How did the old and new cams compare?

Cheers,
Jay
 
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May 27, 2004
1,699
Hunter 30_74-83 Ponce Inlet FL
May I ask where you sourced the "new" impeller? And, was it a brand named product?
 
Apr 8, 2010
1,624
Ericson Yachts Olson 34 28400 Portland OR
We are all glad your trouble shooting worked. One other thing to consider after your initial celebratory beer...
If the cooling hoses are "cracked" and they are 20+ years old, Replace Them Now.
Even if the exterior is not showing a leak, the inner liner can sometimes form an "aneurism" and block a hose. (this happened to a friend of mine, so I know it's possible)
 
Jan 19, 2010
950
Catalina 34 Casco Bay
I'm impressed with your persistence as well. But I'm not sure I understand. Even if the cam was worn down a bit, you'd expect it to still pump some water: just maybe not quite as much. What do you think was going on? How did the old and new cams compare?

Cheers,
Jay
Jay, first off in the grand scheme there was/is wear through the entire pump body. This is the by-product of 34 yrs of work. There was a significant difference in the cams in both length and thickness. The message has been there for a while, but misinterpreted it. Always thought the overheating at 2500RPM was because the impeller was worn and possibly the exchanger was undersized . I had failed to realize that the pump body ( including the cam) was responsible. As stated, the new cam is longer. Like it's predecessor it had bevelled flukes that partially surrounded the inlet and outlet ports. The big difference was that the new cam ran up to the ports where the old one fell short. This prevented a tight fit that in turn altered the ability to form the seal needed to self prime, draw and pump..The cam was $20.00 and the impellers $63.00 ea... go figure !
 
Last edited:
Jan 19, 2010
950
Catalina 34 Casco Bay
May I ask where you sourced the "new" impeller? And, was it a brand named product?
I'll send you a private msg. The source is in the process of making good on the impeller. Not their fault. But they did get them from Westerbeke..
 
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Jan 19, 2010
950
Catalina 34 Casco Bay
We are all glad your trouble shooting worked. One other thing to consider after your initial celebratory beer...
If the cooling hoses are "cracked" and they are 20+ years old, Replace Them Now.
Even if the exterior is not showing a leak, the inner liner can sometimes form an "aneurism" and block a hose. (this happened to a friend of mine, so I know it's possible)
The prospect of an internal blockage is precisely the reason that I replaced the hoses.
 
Jan 19, 2010
950
Catalina 34 Casco Bay
UPDATE..UPDATE. As you know the cam replacement appeared to do the trick. Due to a lack of time yesterday I was only able to check for water flow. Today I had the opportunity to really check this out. After starting the engine, it was allowed to come up to temp. Exhaust water flow appeared OK, so I slipped the mooring and motored out into the channel. Laid on about 1500 RPMs.. All seemed good. Made a few passes by the mooring field. Bumped the throttle to 2300 ( max with the prop on the boat). Almost immediately noted the temperature gauge rising. The throttle was chopped to 1900. Slowly, very slowly the temperature began to drop. Dropped the throttle more to 1500 and the cooling rate increased. Cruised some more at 1500.. Maintained 160 degrees... Decided to sail.. Returning I pushed the RPMs to 1900...The gauge indicated a slight increase to 165ish.. but doable..Decided to check the strainer for debris...Clean.. Restarted the engine ( this is now back on the mooring) Just to make sure.... Looks like I lost the prime checking the strainer.. Tomorrow's another day.. with a cold engine the pump should contract and and offer a better opportunity to prime.. Guess I'm going to be limited to 1900 RPM until the new pump gets made, sold and shipped...

TO BE CONTINUED.....
 
Jun 25, 2004
288
Hunter 306 Pasadena MD
Jay, first off in the grand scheme there was/is wear through the entire pump body. This is the by-product of 34 yrs of work. There was a significant difference in the cams in both length and thickness. The message has been there for a while, but misinterpreted it. Always thought the overheating at 2500RPM was because the impeller was worn and possibly the exchanger was undersized . I had failed to realize that the pump body ( including the cam) was responsible. As stated, the new cam is longer. Like it's predecessor it had bevelled flukes that partially surrounded the inlet and outlet ports. The big difference was that the new cam ran up to the ports where the old one fell short. This prevented a tight fit that in turn altered the ability to form the seal needed to self prime, draw and pump..The cam was $20.00 and the impellers $63.00 ea... go figure !
Got it: thanks for the explanation! And good luck acquiring a new pump, which sounds like the ultimate solution.
 
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Aug 1, 2011
3,959
Catalina 270 255 Wabamun. Welcome to the marina
180 might not be bad, whats the thermostat temperature?
 
Feb 6, 1998
11,436
Canadian Sailcraft 36T Casco Bay, ME
Made a few passes by the mooring field. Bumped the throttle to 2300 ( max with the prop on the boat). Almost immediately noted the temperature gauge rising.
If this is an M-25 Universal/Westerbeke say the engine should be able to hit max rated RPM or 3200 RPM at full throttle.. Sounds like you're over propped too. You may want to check your tachometer calibration with a digital photo tach..
 

jviss

.
Feb 5, 2004
4,627
Tartan 3800 Westport, MA
For what it's worth, my understanding of an experience with liquid cooled engines is that once up to operating temperature they should remain at the thermostat's temperature regardless of load. They are temperature regulated by the cooling system, and the regulation set point is the thermostat temperature. This is important for correct combustion, as a minimum operating temperature, and as an engine protection measure, as a maximum operating temperature. If you find your engine coolant temperature creeping up based on load, then you don't have sufficient cooling, either on the fresh water side (rare) or the raw water side (common). If it creeps down, I would first suspect a bad thermostat.

Also, there could be multiple things going on, like insufficient aw water flow and being over-propped. I will have to defer to the experts, but I don't think over-propping alone should lead to overheating. I would think that with propoer flow, it won't overheat across the entire range you can subject it to with the speed control.
 

RoyS

.
Jun 3, 2012
1,210
Hunter 33 Steamboat Wharf, Hull, MA
Blockage at intake is my guess. Put water hose from dock on intake hose and reverse flush. Probably a jellyfish in there.
 
Sep 30, 2016
302
Hunter 23.5 Patoka Lake, IN
For what it's worth, my understanding of an experience with liquid cooled engines is that once up to operating temperature they should remain at the thermostat's temperature regardless of load. They are temperature regulated by the cooling system, and the regulation set point is the thermostat temperature....
I have to respectfully disagree on the point of engine temp should be no higher than thermostat temp. It is quite common, and normal to go above thermostat temp. The thermostat temp is more a function of having a minimum operating temp, not a maximum.
 

jviss

.
Feb 5, 2004
4,627
Tartan 3800 Westport, MA
I have to respectfully disagree on the point of engine temp should be no higher than thermostat temp. It is quite common, and normal to go above thermostat temp. The thermostat temp is more a function of having a minimum operating temp, not a maximum.
Well, we're going to have to agree to disagree.

The design goal of a cooling system for a liquid cooled internal combustion engine is to keep the engine at constant temperature once it warms up.

If the temp is going above the thermostat temperature then the cooling system is going our of regulation, and this is because of insufficient cooling capacity: basic control theory.

It may indeed be quite common for an engine to go above the thermostat temperature. This is because it is quite common to encounter systems with insufficient cooling capacity. It is not "normal" or desirable.
 
Dec 28, 2015
1,357
Laser, Hunter H30 Cherubini Tacoma
I’d also check the accuracy of your temp gauge. Dirty grounds can make them read high
 
Jul 5, 2011
598
Oday 28 Madison, CT
Those that wander into areas with slime, seaweed, jellyfish etc. might benefit from the so called "South Bay Strainer". Pretty much everything just slides on by. The aggravation of having a plugged intake just is not worth it and you can bet it will happen at the very worst place or time.