My 37c is powered by a salt-water-cooled Yanmar 3QM30 fitted with an aftermarket Sen-Dure fresh water conversion system. The heat exchanger failed last week, so now I've got a salt-water cooled system again. In looking around for an exact replacement for the Sen-Dure exchanger (it's a horizontal tube 2 inches in diameter and 22 inches long with four 5/8 inch inlets/outlets for fresh and salt water, and a 4 inch vertical tube at one end where the pressure cap sits.) I got a quote of more than $700 for a replacement. So I'm looking at alternatives. If any of you have had luck with less expensive generic units on a 3QM30 or similar engine, I'd appreciate a reply. Also, if you know of other sources of supply, new or used. Universal makes a vertical unit, model 300118, that looks as if it might work -- anyone have any experience with this unit? (Only $185 from Boatman's I-Net Marine). Thanks. Capt Walt
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Ed Schenck
Fix it or make one?
My 2QM20 has the exact arrangement that you describe Walt. In fact it looks "homemade" to me. Could you not repair the old one? Or use it as a pattern to make a new one? If not repairable I would cut it open to see just how hard it would be to duplicate. But $700!!? No way. That sounds like the price for the real Yanmar part, a square casting I think. Good luck and let us know the final outcome.
My 2QM20 has the exact arrangement that you describe Walt. In fact it looks "homemade" to me. Could you not repair the old one? Or use it as a pattern to make a new one? If not repairable I would cut it open to see just how hard it would be to duplicate. But $700!!? No way. That sounds like the price for the real Yanmar part, a square casting I think. Good luck and let us know the final outcome.
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Walt G.
Thanks for the response, Ed
Got a better quote from Mack Boring in Mass. Price is down to 3.25 boat units (1 BU = $ 100) plus shipping. Still expensive, but bearable. My guess is that the unit is no longer in production, and Sen-Dure is making one up -- it's going to take a couple of weeks. I will take your suggestion and tear apart the old unit to see how it's put together -- will rebuild it for a spare if possible. Walt -- S/V Moonshine
Got a better quote from Mack Boring in Mass. Price is down to 3.25 boat units (1 BU = $ 100) plus shipping. Still expensive, but bearable. My guess is that the unit is no longer in production, and Sen-Dure is making one up -- it's going to take a couple of weeks. I will take your suggestion and tear apart the old unit to see how it's put together -- will rebuild it for a spare if possible. Walt -- S/V Moonshine
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Ernie Rodriguez
What failed??
I have a similar Sendure heat exchanger that came with my Hunter 36 on a 3GMD engine, and I have repaired it several times. The only portion of it that has failed is the brackets which are soldered on. I glued them on with Marine TEX three times, as they would break off if the bracket that attaches to the back of the engine on the clutch housing would work loose and cause extensive vibration. Recently I removed the heat exchanger from the engine and mounted it on a separate bracket mounted to a plywood bulkhead-sidewall in the engine compartment. Since it connects to the engine with hoses, vibration of the engine is now isolated from the heat exchanger, and it doesn't break off anymore. Other than that, the unit works fine as a heat exchanger. The two end plates began to leak, but by bending them in the opposite direction that they attach, the seal is now leakless! You may be able to salvage yours, a good cleaning will restore its heat exchanging properties. Good luck, Ernie
I have a similar Sendure heat exchanger that came with my Hunter 36 on a 3GMD engine, and I have repaired it several times. The only portion of it that has failed is the brackets which are soldered on. I glued them on with Marine TEX three times, as they would break off if the bracket that attaches to the back of the engine on the clutch housing would work loose and cause extensive vibration. Recently I removed the heat exchanger from the engine and mounted it on a separate bracket mounted to a plywood bulkhead-sidewall in the engine compartment. Since it connects to the engine with hoses, vibration of the engine is now isolated from the heat exchanger, and it doesn't break off anymore. Other than that, the unit works fine as a heat exchanger. The two end plates began to leak, but by bending them in the opposite direction that they attach, the seal is now leakless! You may be able to salvage yours, a good cleaning will restore its heat exchanging properties. Good luck, Ernie
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Kirk Isakson
Sen-Dure Repair
I had a similar problem when I purchased my '80 37-Cutter in '94. I took the unit off and had it fixed at a radiator shop. The cost was less than $50.
I had a similar problem when I purchased my '80 37-Cutter in '94. I took the unit off and had it fixed at a radiator shop. The cost was less than $50.
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Wallt G.
Ernie,
Thanks for the info. My Sen-Dure unit was also engine-mounted, and I too had problems with the brackets breaking. Sounds as if you did the same thing I did, mounting it on the engine compartment bulkhead (I used 2" muffler clamps to bolt it onto the stbd bulkhead -- works great). But in response to your question, it appears that the unit failed internally, since I now have salt water on what should be the antifreeze side. But at least the engine was originally designed for salt water operation, so I can run it that way until I get the replacement unit (just had to run the overflow tube into the bilge to keep the salt water overflow out of the engine compartment. Thanks again for the response. Capt Walt -- S/V Moonshine ('79 37c)
Thanks for the info. My Sen-Dure unit was also engine-mounted, and I too had problems with the brackets breaking. Sounds as if you did the same thing I did, mounting it on the engine compartment bulkhead (I used 2" muffler clamps to bolt it onto the stbd bulkhead -- works great). But in response to your question, it appears that the unit failed internally, since I now have salt water on what should be the antifreeze side. But at least the engine was originally designed for salt water operation, so I can run it that way until I get the replacement unit (just had to run the overflow tube into the bilge to keep the salt water overflow out of the engine compartment. Thanks again for the response. Capt Walt -- S/V Moonshine ('79 37c)
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OBX Sailor
Having a cooling problem too
I have a 3QM30 alos in my cutter. Just recently it began overheating after about 30-60 minutes. I have checked the raw water strainer clear and flowing, changed the impeller, hoses for leaks, flushed the system with acid solution and rinse (twice) and am running out of possible fixes. The engine only has about 860 hrs total. Any suggestions/solutions? thanks, OBX Sailor
I have a 3QM30 alos in my cutter. Just recently it began overheating after about 30-60 minutes. I have checked the raw water strainer clear and flowing, changed the impeller, hoses for leaks, flushed the system with acid solution and rinse (twice) and am running out of possible fixes. The engine only has about 860 hrs total. Any suggestions/solutions? thanks, OBX Sailor
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Walt G
3QM30 overheating
Check the outflow of water from your exhaust. If you're not getting much water outflow, you've got a restriction somewhere on the salt-water side. Then try checking the thermostats (two small ones). They might be sticking closed, and that would cause an overheat. If you've got the aftermarket sen-dure cooler, try removing the end plate and inspecting the cooling tubes for blockage. Make sure they're clear -- you can rod them out using a wooden dowel or similar tool, but be careful not to damage the tubes, which can and do wear thin with time. If you've got a water heater connected to the engine, check the routing of the hoses to make sure you don't have any loops that could cause the hose to become air bound (I had this problem -- a bubble of air in the hose was restricting coolant flow and caused overheating until I purged the line of air). Good luck. Capt Walt -- s/v Moonshine.
Check the outflow of water from your exhaust. If you're not getting much water outflow, you've got a restriction somewhere on the salt-water side. Then try checking the thermostats (two small ones). They might be sticking closed, and that would cause an overheat. If you've got the aftermarket sen-dure cooler, try removing the end plate and inspecting the cooling tubes for blockage. Make sure they're clear -- you can rod them out using a wooden dowel or similar tool, but be careful not to damage the tubes, which can and do wear thin with time. If you've got a water heater connected to the engine, check the routing of the hoses to make sure you don't have any loops that could cause the hose to become air bound (I had this problem -- a bubble of air in the hose was restricting coolant flow and caused overheating until I purged the line of air). Good luck. Capt Walt -- s/v Moonshine.
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OBX Sailor
Thanks
Thanks, I will try this today. I have changed the T-stats and will check for air in the lines, water flow out the stern is excellent. OBX Sailor
Thanks, I will try this today. I have changed the T-stats and will check for air in the lines, water flow out the stern is excellent. OBX Sailor
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tony giaccio
air compressor dealers
call local air compressor dealers.they may have one in stock.they use sendur to cool compressed air.they get big discount and it's not considered a marine product. tony
call local air compressor dealers.they may have one in stock.they use sendur to cool compressed air.they get big discount and it's not considered a marine product. tony
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