I bought my 460 18 months ago and have not been able to exceed 2800 rpm's without overheating my Yanmar (max is 3700). Every inch of the raw and freshwater system including strainers, impellers (new twice), heat exchanger, mixing elbow, etc, have been checked and rechecked as perfect. Raw water flow is excellent and the mixing elbow remains cool to the touch throughout the rpm range. I had a local Yanmar dealer come out and test everything today using a cool laser temperature probe. They are of the conclusion that the exhaust routing between the engine and water lift muffler may have a droop allowing too much standing water in the hose causing too much back pressure for the exhaust. We are going to step two asap and test out that theory with different test equipment. In the mean time, has anyone else been thru seemingly unsolvable overheating problems on this model?
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Call Bob Kilian at Bay Props.
Chuck: I would say that you are over propped. This is the same symptoms that we had on our H31. Reduced the pitch and all was fine. Bob Kilian's number is 510/337-9122
Chuck: I would say that you are over propped. This is the same symptoms that we had on our H31. Reduced the pitch and all was fine. Bob Kilian's number is 510/337-9122
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Gordon Myers
Temp. gauge &/or Sender?
Are you sure that the engine is overheating? I had a faulty engine temp. gauge & later a faulty sending unit. The engine both time was never overheating.
Are you sure that the engine is overheating? I had a faulty engine temp. gauge & later a faulty sending unit. The engine both time was never overheating.
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Chuck Drake
Temp Guage
The temp guage and beeper calibrations were confirmed today with my mechanic using a Snap On Laser temp tester...I just wish it were that simple!!! Thanks for the thought though...
The temp guage and beeper calibrations were confirmed today with my mechanic using a Snap On Laser temp tester...I just wish it were that simple!!! Thanks for the thought though...
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Chuck Drake
Prop
Thanks for the thought but I've already been thru all of this with Martec...I had my diver adjust my pitch and now get spec 3700 rpms and, unfortunately, only gave me minimal improvement...ARGH!
Thanks for the thought but I've already been thru all of this with Martec...I had my diver adjust my pitch and now get spec 3700 rpms and, unfortunately, only gave me minimal improvement...ARGH!
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James
backpressure is a possibility
Although its kind of a rare case. If you are sure that there is no clog in the cooling system then this would be a good place to check. If you are inspecting the water flow for the cooling system just by looking at the overall output you are just making an educated guess. I once cured an "uncurable" overheating problem on a Volvo marine diesel by detaching portions of the cooling system one piece at a time and running water through them with a hose checking the flow of each piece. A rather innocent looking connector tube turned out to be plugged almost completely. The water flow out the exhast was normal looking at all times because the water just took a different path on this design. You can check the backpressure with a manometer. Its a rather cheap testing tool, about 30 dollars last time I bought one. You can then install a fitting ( as close to the engine exhaust as possible ) to attach it to and compare the backpressure to specs from Yanmar. Be sure to test the backpressure at the RPM point where you are having trouble and UNDERLOAD as the engine will produce considerably more exhaust gas underload than it will while in neutral at the dock.
Although its kind of a rare case. If you are sure that there is no clog in the cooling system then this would be a good place to check. If you are inspecting the water flow for the cooling system just by looking at the overall output you are just making an educated guess. I once cured an "uncurable" overheating problem on a Volvo marine diesel by detaching portions of the cooling system one piece at a time and running water through them with a hose checking the flow of each piece. A rather innocent looking connector tube turned out to be plugged almost completely. The water flow out the exhast was normal looking at all times because the water just took a different path on this design. You can check the backpressure with a manometer. Its a rather cheap testing tool, about 30 dollars last time I bought one. You can then install a fitting ( as close to the engine exhaust as possible ) to attach it to and compare the backpressure to specs from Yanmar. Be sure to test the backpressure at the RPM point where you are having trouble and UNDERLOAD as the engine will produce considerably more exhaust gas underload than it will while in neutral at the dock.
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Chuck Drake
Backpressure
The backpressure test is next on my agenda...won't have a chance to get to it for a couple of weeks but I guess it will wait for me!
The backpressure test is next on my agenda...won't have a chance to get to it for a couple of weeks but I guess it will wait for me!
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Dan Grosz
How about the heat exchanger cap?
Defective cap may not be able to maintain adequate pressure and therefore will run hotter.
Defective cap may not be able to maintain adequate pressure and therefore will run hotter.
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Wayne Lenoir
Similar problem with straight antifreeze
Your problem seems thoroughly investigated. However, A few months after getting our 2002 450, we discovered a overheating problem when running at higher rpm's. After much investigation the cause turned out to be caused by undiluted anti-freeze; mixed in the proper amount of water, no more overheating.
Your problem seems thoroughly investigated. However, A few months after getting our 2002 450, we discovered a overheating problem when running at higher rpm's. After much investigation the cause turned out to be caused by undiluted anti-freeze; mixed in the proper amount of water, no more overheating.
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John Rollins
rpm's
I find that the sweet spot for my 460 is about 2400 rpms. Not sure that lowering your rpm's would solve your problem, but I am not sure what you are gaining by running at 3700. Good luck, John
I find that the sweet spot for my 460 is about 2400 rpms. Not sure that lowering your rpm's would solve your problem, but I am not sure what you are gaining by running at 3700. Good luck, John
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Bradley Cavedo
Crusine RPMs
My understanding is that you are supposed to do most of your motorcrusing at 80% of your maximum in-gear RMPs. On the Passage 42, that maximum is not supposed to be below 3600 [62HP turbo Yanmar]. If it won't make 3600, then the prop is too big or too pitched. Our max RPM is 3850 [we are slightly under-proped]. So we cruise at 2900 to 3100 depending on conditions. Every now and then we will run at 3500 for about an hour to burn off carbon deposits. I am not sure how John is running at 2400 without causing carbon buildup and perhaps other damage.
My understanding is that you are supposed to do most of your motorcrusing at 80% of your maximum in-gear RMPs. On the Passage 42, that maximum is not supposed to be below 3600 [62HP turbo Yanmar]. If it won't make 3600, then the prop is too big or too pitched. Our max RPM is 3850 [we are slightly under-proped]. So we cruise at 2900 to 3100 depending on conditions. Every now and then we will run at 3500 for about an hour to burn off carbon deposits. I am not sure how John is running at 2400 without causing carbon buildup and perhaps other damage.
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Bruce
Have you checked your prop?
I know this sounds too simple and illogical, but last year I had the same problem and took every part of the cooling system off and checked or replaced, with no success. Problem was that my prop was covered with barnacles and when I cleaned it, the problem went away. Those suckers grow fast and I was very surprised that they made that much difference. Bruce
I know this sounds too simple and illogical, but last year I had the same problem and took every part of the cooling system off and checked or replaced, with no success. Problem was that my prop was covered with barnacles and when I cleaned it, the problem went away. Those suckers grow fast and I was very surprised that they made that much difference. Bruce
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Paul Akers
Pressure Cap?
Stange as it may seem, the "radiator" (Heat exchanger) pressure cap could be defective. I recently had a discussion with a powerboater who mentioned that one of his engines ran 20 degrees hotter than the other. He was puzzled. So on a whim he switched the caps and the problem shifted to the other engine. WFIW, that could be your problem. Good Luck!
Stange as it may seem, the "radiator" (Heat exchanger) pressure cap could be defective. I recently had a discussion with a powerboater who mentioned that one of his engines ran 20 degrees hotter than the other. He was puzzled. So on a whim he switched the caps and the problem shifted to the other engine. WFIW, that could be your problem. Good Luck!
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Ray
Overheat
This may not help but I had a Hunter 34 with 3GMF overheating at higher RPM's. Turned out the "fresh water pump" bypass line was blocked (sediment). Cleaned it and that was all i needed, runs cool as ever. Before that I replace raw water impellers etc. Of course my Hunter was an '83 and could possibly expect this happen if the Anti-Freeze or water is never changed.
This may not help but I had a Hunter 34 with 3GMF overheating at higher RPM's. Turned out the "fresh water pump" bypass line was blocked (sediment). Cleaned it and that was all i needed, runs cool as ever. Before that I replace raw water impellers etc. Of course my Hunter was an '83 and could possibly expect this happen if the Anti-Freeze or water is never changed.
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