I have a 2005 hunter 33 with the 29HP Yanmar engine. I have 270 hours on the engine and the overheating alarm is sounding after about 4 minutes whenever I exceed 3200 rpm. This is new. We have used the boat at 3200 RPM for the first 250 hours without incident. I have done all the obvious things - checked the impeller in the raw water pump; cleaned the exhaust injection nipple; checked the pump belt and the raw water filter. There is lots of water going through the heat exchanger and out of the exhaust. I notice that the insulation on the companionway stairs presses directly onto the top of the engine - just by the thermostat and the temperature gauge sensor. Do other owners notice the same issue? Have any other owners had a problem with overheating?
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3200?
3200 rpm seems a tad high to me, especially during the initial break-in period. Back it down to about 2800 and see what happens.
3200 rpm seems a tad high to me, especially during the initial break-in period. Back it down to about 2800 and see what happens.
Look at coolant hoses
While at a hunter rendevouz at Catalina Island, I ran into a couple of H33's that had overheat problems at even lower rpms. Both found that one of the coolant hoses that comes off the engine vertically, to a loop, and then down, had a kink develop in the loop that restricted flow enough to cause the overheating. Flow out of the exhaust appeared ok - but there was just enough restriction to cause the overheat condition. Maybe yours is not too much of a restriction and allows you to get to the higher rpm before overheating. As far as rpms go, 3200 is ok according to the manual. I think you can go to almost 3400 according to the manual - however fuel consumption goes way up above 3000. Michael
While at a hunter rendevouz at Catalina Island, I ran into a couple of H33's that had overheat problems at even lower rpms. Both found that one of the coolant hoses that comes off the engine vertically, to a loop, and then down, had a kink develop in the loop that restricted flow enough to cause the overheating. Flow out of the exhaust appeared ok - but there was just enough restriction to cause the overheat condition. Maybe yours is not too much of a restriction and allows you to get to the higher rpm before overheating. As far as rpms go, 3200 is ok according to the manual. I think you can go to almost 3400 according to the manual - however fuel consumption goes way up above 3000. Michael
My Hunter 33 with the 3YM30
I too used to run my 3YM30 at 3000-3200. For the current season though I have not been able to run it over 2800 for any extended amount of time. 2800 allows me around 6 knots so I have been OK with it. This summer though I had an overheating incident in a remote section of downeast Maine, just a few miles from the Canadian border. I couldn't get the engine much above half speed before it would overheat. I checked the obvious things like strainer, impeller, etc. In fact just to be sure I changed out the impeller. We sailed (we are a sailboat after all) back down to Northeast harbor where I went through a succession of Yanmar support people. They agreed that I had done all of the 'normal' things and scheduled me into Wayfair Marine in Camden the next day. We sailed over and the next day began the process to caustic strip the cooling system. HAlf way through this procedure the mechanic had an idea. We removed the strainer and with a pipe wrench removed the brass elbow from the through hull to the strainer. Sure enough, just **before** the ball in the seacock (the hull side) there was enough seaweed jammed into there to make a salad. We guessed with the new impeller in there there was enough suction to draw enough water to allow the engine some cooling capability. Once cleared the engine ran fine. This winter I will have to add a pipe wrench to my onboard toolkit as I would never have been able to disassemble this myself in the boonies of Maine. We still only are able to run the engine at about 2800 RPM but we are satisfied. You may want to search the archives. I believe a gentleman by the name of John Ehricht had a series of 3YM30 overheating problems last year. Unfourtunately I believe he recently lost his boat in hurricane Katrina. Good Luck and let us know what you find out. Andy
I too used to run my 3YM30 at 3000-3200. For the current season though I have not been able to run it over 2800 for any extended amount of time. 2800 allows me around 6 knots so I have been OK with it. This summer though I had an overheating incident in a remote section of downeast Maine, just a few miles from the Canadian border. I couldn't get the engine much above half speed before it would overheat. I checked the obvious things like strainer, impeller, etc. In fact just to be sure I changed out the impeller. We sailed (we are a sailboat after all) back down to Northeast harbor where I went through a succession of Yanmar support people. They agreed that I had done all of the 'normal' things and scheduled me into Wayfair Marine in Camden the next day. We sailed over and the next day began the process to caustic strip the cooling system. HAlf way through this procedure the mechanic had an idea. We removed the strainer and with a pipe wrench removed the brass elbow from the through hull to the strainer. Sure enough, just **before** the ball in the seacock (the hull side) there was enough seaweed jammed into there to make a salad. We guessed with the new impeller in there there was enough suction to draw enough water to allow the engine some cooling capability. Once cleared the engine ran fine. This winter I will have to add a pipe wrench to my onboard toolkit as I would never have been able to disassemble this myself in the boonies of Maine. We still only are able to run the engine at about 2800 RPM but we are satisfied. You may want to search the archives. I believe a gentleman by the name of John Ehricht had a series of 3YM30 overheating problems last year. Unfourtunately I believe he recently lost his boat in hurricane Katrina. Good Luck and let us know what you find out. Andy
Restrictions in the supply hose
Thanks for this suggestion. The hose is bent very sharply at that point. It also becomes compressed by the companionway stairs when they are in place. I am going to try re-routing the hose and strapping it so that the tendecy to kink is minimised. I will post the results ina day or two.
Thanks for this suggestion. The hose is bent very sharply at that point. It also becomes compressed by the companionway stairs when they are in place. I am going to try re-routing the hose and strapping it so that the tendecy to kink is minimised. I will post the results ina day or two.
Safe RPM for Yanmar 3YM30
This reply to Steve O's comment about 3200 RPM. My Yanmar mechanic tellls me that one should run the engine at 85% of max revs for five minutes or so just before docking. This is especially necessary if you run it at mid-range revs for most of the time. The rationale is that running it very hot for a few minutes prevents the exhaust elbow coking up prematurely. Since the tachometers on these engines are variable you need to run at max revs for a few seconds to see what your tach reads and then do your calculations accordingly. My engine runs up to 3800 when flat out (for a few seconds), so I think that 3400 for the five minute run in should be OK and 3200 should be possible all day long (if I want to burn all that diesel fuel!) It was running the engine at the 3400 that started all this overheating issue. My Yanmar dealer tells me that 5 mins of 3400 should be possible. Anyway as a result of this post I have a few more things to try. Thanks everyone. I will post results in a day or so after I get a chance to get out on the water again.
This reply to Steve O's comment about 3200 RPM. My Yanmar mechanic tellls me that one should run the engine at 85% of max revs for five minutes or so just before docking. This is especially necessary if you run it at mid-range revs for most of the time. The rationale is that running it very hot for a few minutes prevents the exhaust elbow coking up prematurely. Since the tachometers on these engines are variable you need to run at max revs for a few seconds to see what your tach reads and then do your calculations accordingly. My engine runs up to 3800 when flat out (for a few seconds), so I think that 3400 for the five minute run in should be OK and 3200 should be possible all day long (if I want to burn all that diesel fuel!) It was running the engine at the 3400 that started all this overheating issue. My Yanmar dealer tells me that 5 mins of 3400 should be possible. Anyway as a result of this post I have a few more things to try. Thanks everyone. I will post results in a day or so after I get a chance to get out on the water again.
Cosmoline
I had a 33 with the 3YM30 and went through this whole issue. I just spoke with a dealer in NC also who is quite familiar with this issue. Call Don Martin at Hunter. The prolem is that Yanmar did not take the cosmoline off of the heat exchanger when they assembled the engine. As time passes, the cosmoline bakes on the coils and prevents the heat exchange to take place. The heat exchanger must be taken out and the cosmoline removed.
I had a 33 with the 3YM30 and went through this whole issue. I just spoke with a dealer in NC also who is quite familiar with this issue. Call Don Martin at Hunter. The prolem is that Yanmar did not take the cosmoline off of the heat exchanger when they assembled the engine. As time passes, the cosmoline bakes on the coils and prevents the heat exchange to take place. The heat exchanger must be taken out and the cosmoline removed.
There is a solution to overheating 3YM30
David, Your dealer should have notified you by now that, there is and has (for a while) been an overheating problem caused by using 'bad' coolant. This results in a subsequent problem with the heat exchanger on some 3YM20/30 engines. My boat is a 2004 Hunter 33(hull 166) and the overheating problems began after only 20 hours engine-time. It is now up to 70 hours. The dealer in Toronto was not and has not been helpful. Throughout last summer the problem continued intermittently but as has been said on this and other forums, the overheating alarm usually goes off at RPMs anywhere between 2400 and up. With my engine, after 10 mins at 2600 RPM it was sure to go off, so I kept below that level. That is, until a few weeks ago. I got caught in roughish weather in a busy part of the Thousand Islands and really needed that engine - but you guessed it, the overheating alarm kept sounding. In that instance at around 2400 RPMs. I had to let the engine cool off for a while then restart. After about an hour of careful throttle management I managed to keep the engine alarm quiet at 1800 RPM. At the time I was slamming into a heavy swell with the wind on my nose gusting to 30 kts I could only manage about 2 kts boatspeed. Sails were not much of an option because of shoals and having to navigate through a narrow passage. The next day I call the Yanmar rep in Toronto and was informed that Yanmar is currently rectifying the problem on all the engines that have reported overheating. My turn came last Friday. I see from this forum Hunter blames Yanmar but then Hunter always blames someone else. Yanmar says the problem is with Hunter. The Yanmar reptold me Yanmar ships all its engines in crates "dry" to Hunter, who then adds coolant to the engines. Unfortunately, 100% coolant was added to a fair number of these engines. The Yanmar guy said the mixture should have been a 50/50 mix. Of course the 100% coolant boils at a lower temperature. To make matters worse, the boiling coolant leaves a residue in the heat exchanger which builds up and inhibits the water flow and in turn the cooling efficiency of the system. The Yanmar rep flushed out my entire cooling system and removed and replaced the heat exchanger. He refilled the system with clean 50/50 mix of pink (Texaco long life??)coolant starting at the heater (through its hoses then reconnected them). He then slowly filled the rest of the system (by the way the green coolant is verboten) taking care to avoid creating airlocks. The engine was run for about 20 minutes at idle then we went out for a test run. Through an hour of high RPM use the engine performed flawlessly. We got it up to 3600 RPM and kept it there for quite a while and the hottest temperature (he used some type of electronic gizmo to measure the temperature) the engine only got up to 83 deg C while at 3600 RPM for several minutes. I am told that the alarm goes off at 95 deg C and stops at 93 deg C. However the rep said on some engines it could sound as low as 93 deg C and stop at 91 deg C. He showed me that at 3200 RPM the engine temp remained at 73 deg C. I am finally convinced that the overheating problem is solved on my 3YM30. My next project is to fit a temperature gauge and retain my alarm system (belts and braces). Yanmar is not enthusiastic about helping with a solution but suggests the additional sender probe should go out of the water-heater engine outlet. If you want your overheating problem to go away by-pass Port Credit and call Danny at Total Power in Mississauga.
David, Your dealer should have notified you by now that, there is and has (for a while) been an overheating problem caused by using 'bad' coolant. This results in a subsequent problem with the heat exchanger on some 3YM20/30 engines. My boat is a 2004 Hunter 33(hull 166) and the overheating problems began after only 20 hours engine-time. It is now up to 70 hours. The dealer in Toronto was not and has not been helpful. Throughout last summer the problem continued intermittently but as has been said on this and other forums, the overheating alarm usually goes off at RPMs anywhere between 2400 and up. With my engine, after 10 mins at 2600 RPM it was sure to go off, so I kept below that level. That is, until a few weeks ago. I got caught in roughish weather in a busy part of the Thousand Islands and really needed that engine - but you guessed it, the overheating alarm kept sounding. In that instance at around 2400 RPMs. I had to let the engine cool off for a while then restart. After about an hour of careful throttle management I managed to keep the engine alarm quiet at 1800 RPM. At the time I was slamming into a heavy swell with the wind on my nose gusting to 30 kts I could only manage about 2 kts boatspeed. Sails were not much of an option because of shoals and having to navigate through a narrow passage. The next day I call the Yanmar rep in Toronto and was informed that Yanmar is currently rectifying the problem on all the engines that have reported overheating. My turn came last Friday. I see from this forum Hunter blames Yanmar but then Hunter always blames someone else. Yanmar says the problem is with Hunter. The Yanmar reptold me Yanmar ships all its engines in crates "dry" to Hunter, who then adds coolant to the engines. Unfortunately, 100% coolant was added to a fair number of these engines. The Yanmar guy said the mixture should have been a 50/50 mix. Of course the 100% coolant boils at a lower temperature. To make matters worse, the boiling coolant leaves a residue in the heat exchanger which builds up and inhibits the water flow and in turn the cooling efficiency of the system. The Yanmar rep flushed out my entire cooling system and removed and replaced the heat exchanger. He refilled the system with clean 50/50 mix of pink (Texaco long life??)coolant starting at the heater (through its hoses then reconnected them). He then slowly filled the rest of the system (by the way the green coolant is verboten) taking care to avoid creating airlocks. The engine was run for about 20 minutes at idle then we went out for a test run. Through an hour of high RPM use the engine performed flawlessly. We got it up to 3600 RPM and kept it there for quite a while and the hottest temperature (he used some type of electronic gizmo to measure the temperature) the engine only got up to 83 deg C while at 3600 RPM for several minutes. I am told that the alarm goes off at 95 deg C and stops at 93 deg C. However the rep said on some engines it could sound as low as 93 deg C and stop at 91 deg C. He showed me that at 3200 RPM the engine temp remained at 73 deg C. I am finally convinced that the overheating problem is solved on my 3YM30. My next project is to fit a temperature gauge and retain my alarm system (belts and braces). Yanmar is not enthusiastic about helping with a solution but suggests the additional sender probe should go out of the water-heater engine outlet. If you want your overheating problem to go away by-pass Port Credit and call Danny at Total Power in Mississauga.
Beg to disagree
with John in Ontario that the coolant mixture was the source of his overheating problem. Think of your car, unless you live in places with temps less than 32F or above 85F, the coolant mixture isn't going to get your car running hot . The same principle applies to your boat engine. There was probably air trapped in your cooling system. Your Yanmar rep flushed and refilled and maybe even vented all of the air which "solved" your problem. Again, this also applies to your car. Change your radiator or cooling pump and don't properly vent the system then your car will also over heat. On my boat, there is a small vent valve on the inlet to the water heater. I could vent the system by opening that valve slightly with the engine running. When all air bubbles has excaped, the system is vented.
with John in Ontario that the coolant mixture was the source of his overheating problem. Think of your car, unless you live in places with temps less than 32F or above 85F, the coolant mixture isn't going to get your car running hot . The same principle applies to your boat engine. There was probably air trapped in your cooling system. Your Yanmar rep flushed and refilled and maybe even vented all of the air which "solved" your problem. Again, this also applies to your car. Change your radiator or cooling pump and don't properly vent the system then your car will also over heat. On my boat, there is a small vent valve on the inlet to the water heater. I could vent the system by opening that valve slightly with the engine running. When all air bubbles has excaped, the system is vented.
Fact not theory
Disagree all you want David from BC. I went through the 'overheating' saga over two boating seasons so my contribution is based on experiencing the problem and the solution, not relying on theory or car examples. Check this forum's archives for earlier this year. Somewhere in there I explained how I bled airlocks out of that 3YM30 engine on the advice of a diesel technician and for a while thought the overheating problem was gone. Back then I spent about an hour bleeding all the bubbles out (engine running at moderate RPMs with pressure cap off) by slowly adding a fair amount of top up coolant to the system until it was full and stayed full - and no bubbles left. This provided some respite from overheating but did not totally solve the problem. What apparently happened was that by adding (my prepared) 55/45 mix of new coolant it diluted the original 100% mixture in the engine to something less than 100%. That dilution marginally increased the boiling threshold of the coolant. However it was not sufficient to stop the overheating at higher RPMs. As I said, if you run the engine with the pressure cap off and there is an airlock in the system you will see the level of coolant drop as the air bubbles come rushing up. In this (recent) instance that was not the case because the coolant level remained full to the brim even during overheating - and there were absolutely no bubbles to be seen. What in fact continued to cause my problem was the residue left in that heat exchanger from previous boiling of the 100% coolant concentrate. What I did not say in my previous submission was, the Yanmar rep showed me the colour of the coolant he flushed out of my engine and it was dark blood red - not pink. He said the frequent overheating/boiling had broken down the molecular structure of the coolant causing the colour change and also causing it to leave a residue in the heat exchanger. So if you believe that bleeding out airlocks in this particular cooling system with this level of coolant concentrate will solve this particular problem - good luck. I would have agreed with you earlier this year but now I have seen (and experienced) the light. Finally, if it was an airlock issue I wonder why are there airlocks in so many new 3YM20/30 engines across North America? Airlocks are not covered by the Yanmar warranty so why does Yanmar go through the hassle of replacing so many heat exchangers at no charge? Nonetheless I expect the overheating issue will now have come to an end with the more recent production boats with the 3YM engines because someone at the source finally realised they should not put 100% coolant in an engine.
Disagree all you want David from BC. I went through the 'overheating' saga over two boating seasons so my contribution is based on experiencing the problem and the solution, not relying on theory or car examples. Check this forum's archives for earlier this year. Somewhere in there I explained how I bled airlocks out of that 3YM30 engine on the advice of a diesel technician and for a while thought the overheating problem was gone. Back then I spent about an hour bleeding all the bubbles out (engine running at moderate RPMs with pressure cap off) by slowly adding a fair amount of top up coolant to the system until it was full and stayed full - and no bubbles left. This provided some respite from overheating but did not totally solve the problem. What apparently happened was that by adding (my prepared) 55/45 mix of new coolant it diluted the original 100% mixture in the engine to something less than 100%. That dilution marginally increased the boiling threshold of the coolant. However it was not sufficient to stop the overheating at higher RPMs. As I said, if you run the engine with the pressure cap off and there is an airlock in the system you will see the level of coolant drop as the air bubbles come rushing up. In this (recent) instance that was not the case because the coolant level remained full to the brim even during overheating - and there were absolutely no bubbles to be seen. What in fact continued to cause my problem was the residue left in that heat exchanger from previous boiling of the 100% coolant concentrate. What I did not say in my previous submission was, the Yanmar rep showed me the colour of the coolant he flushed out of my engine and it was dark blood red - not pink. He said the frequent overheating/boiling had broken down the molecular structure of the coolant causing the colour change and also causing it to leave a residue in the heat exchanger. So if you believe that bleeding out airlocks in this particular cooling system with this level of coolant concentrate will solve this particular problem - good luck. I would have agreed with you earlier this year but now I have seen (and experienced) the light. Finally, if it was an airlock issue I wonder why are there airlocks in so many new 3YM20/30 engines across North America? Airlocks are not covered by the Yanmar warranty so why does Yanmar go through the hassle of replacing so many heat exchangers at no charge? Nonetheless I expect the overheating issue will now have come to an end with the more recent production boats with the 3YM engines because someone at the source finally realised they should not put 100% coolant in an engine.
Sorry David from BC
My apology to David in BC. My last message should have been addressed to Ben at Mayport.
My apology to David in BC. My last message should have been addressed to Ben at Mayport.
Sorry
John, didn't mean anything negative. Just drawing from my experience with automotive engine cooling system and indicating another possibility. This type of peoblem is common with automotive engines that is why there are bleed ports on the side of most engine blocks or some people advise turn thermostat to high heat when refilling your radiator. If you read the forum you will see that most of the problems occur with NEW engings! Bottom line, air pockets in your system will prevent flow of coolant throughout the engine resulting in overheating.
John, didn't mean anything negative. Just drawing from my experience with automotive engine cooling system and indicating another possibility. This type of peoblem is common with automotive engines that is why there are bleed ports on the side of most engine blocks or some people advise turn thermostat to high heat when refilling your radiator. If you read the forum you will see that most of the problems occur with NEW engings! Bottom line, air pockets in your system will prevent flow of coolant throughout the engine resulting in overheating.
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