just purchased a '98 376. Can someone tell me (or where to find it) is the correct cruising RPM on this motor? I don't want to run it too high for too long when I return from Ensenada.
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70-80% of max rated RPM.
Bob: I believe that your engine is rated at 3600 RPM max. The general rule is 70-80% (2500-3000rpm) of the max rating. If you run your Yanmar at too high of an RPM for a sustained period they will tend to give you and over-heat alarm. If this happens you need to back off the RPM's. This can sometimes happen because you have a blocked raw water intake, worn raw water impeller, or a restricted mixing elbow too. If your problem is from over reving the engine, you should not shut down your engine, but back off the throttle to a lower RPM until it gets down to the normal operating range. This will help cool the engine down properly. If the intake is blocked or you have a bad impeller you really don't have much choice other than shutting it down. The thermal switch on these engines usually go off before they are in the critical range anyway so there is some margin there. You will know if the intake is blocked by removing the lid on the strainer. If no water is comming in you have some sort of blockage. The impeller or the blocked mixing elbow are a little more difficult to diagnosis. PS: Is this a turbo engine? If it is you should never shut it down HOT. Always let a turbo engine idle for several minutes before shutting down. This is also a good idea for non-turbo engine too.
Bob: I believe that your engine is rated at 3600 RPM max. The general rule is 70-80% (2500-3000rpm) of the max rating. If you run your Yanmar at too high of an RPM for a sustained period they will tend to give you and over-heat alarm. If this happens you need to back off the RPM's. This can sometimes happen because you have a blocked raw water intake, worn raw water impeller, or a restricted mixing elbow too. If your problem is from over reving the engine, you should not shut down your engine, but back off the throttle to a lower RPM until it gets down to the normal operating range. This will help cool the engine down properly. If the intake is blocked or you have a bad impeller you really don't have much choice other than shutting it down. The thermal switch on these engines usually go off before they are in the critical range anyway so there is some margin there. You will know if the intake is blocked by removing the lid on the strainer. If no water is comming in you have some sort of blockage. The impeller or the blocked mixing elbow are a little more difficult to diagnosis. PS: Is this a turbo engine? If it is you should never shut it down HOT. Always let a turbo engine idle for several minutes before shutting down. This is also a good idea for non-turbo engine too.
D
Don Alexander
Cruising RPM for a 376
Hi Bob, Interesting to learn from Steve Dion about overheating, and I know my impeller and water injection elbow are fine. Thanks Steve. I usually chug along in my 376 at about 2750 - 2850 and everything seems very happy and little extra speed comes at full throttle. However .... This summer I was out to see the big Jubilee Regatta on the Solent and was trying to maximise the time and photo opportunities of the Americas Cuppers and the J Class. Without realising it we ran at full throttle for nearly an hour. We were directly ahead of the oncoming fleet when the overheat alarm went off. My pal who was driving the boat immediately shut down. Now we were engineless with no sails either and right in the path of a fleet of a hundred VERY competitive yachts all hard on the wind. I could not see them troubling to avoid us. Suddenly I thought of a solution. We turned on the hot taps of all three handbasins and let the water run for a couple of minutes. This took some heat out of the fresh water cooling system. On switch on the engine overheat alarm still sounded but in a very few seconds it went off as the cooler water from the calorifier began to circulate and we were able to get clear of the fleet - but it was a close run thing. She ran perfectly for the rest of the day. Regatta was great though. Hope you enjoy your 376. Regards, Don
Hi Bob, Interesting to learn from Steve Dion about overheating, and I know my impeller and water injection elbow are fine. Thanks Steve. I usually chug along in my 376 at about 2750 - 2850 and everything seems very happy and little extra speed comes at full throttle. However .... This summer I was out to see the big Jubilee Regatta on the Solent and was trying to maximise the time and photo opportunities of the Americas Cuppers and the J Class. Without realising it we ran at full throttle for nearly an hour. We were directly ahead of the oncoming fleet when the overheat alarm went off. My pal who was driving the boat immediately shut down. Now we were engineless with no sails either and right in the path of a fleet of a hundred VERY competitive yachts all hard on the wind. I could not see them troubling to avoid us. Suddenly I thought of a solution. We turned on the hot taps of all three handbasins and let the water run for a couple of minutes. This took some heat out of the fresh water cooling system. On switch on the engine overheat alarm still sounded but in a very few seconds it went off as the cooler water from the calorifier began to circulate and we were able to get clear of the fleet - but it was a close run thing. She ran perfectly for the rest of the day. Regatta was great though. Hope you enjoy your 376. Regards, Don
Hi Don.
Don: We have things other than seaweed in our part of the world. I have sucked up minnows, leaves etc. into the raw water strainer. I usually back off the throttle to about 1000-1500 rpms for a minute or so and the alarm will go off. There is usually enough water comming in that it allows the engine to cool down enough and not cause any damage. Once the alarm quits is then shut down the engine and immediately inspect the raw water strainer. If there is no water comming in then the problem is the thru hull is blocked. The last time this happened we had sucked up some gravel from the bottom of the harbor from being stuck. I got a piece of stiff wire and cleared the thru hull and we were off again after just a few minutes. If the strainer is not blocked and you are still taking on water, its time to inspect further down the line. Check your belts to make sure that they are not broken or loose. You can actually do this first but my experience has been best starting at one end and working to the other. Then the next item is the impeller. They usually do not completely go away on you, they usually just loose a blade or two. If you back off on the power you can sometimes limp back to the harbor or an anchorage and replace it there. If all of these things check out OKAY, you are then faced with some tougher decisions like the heat exchanger or the elbow and exhaust hose. These are not things that can normally be fixed without being at the dock. The elbow is a good item to have on a every 2-5 year maintenance list. If you have an old one that is in good shape you can have it as a spare and recycle them until one of them corrodes out. If you leave them in for longer than the 2-5 years they normally burn out (especially in salt water) and just need to be replaced.
Don: We have things other than seaweed in our part of the world. I have sucked up minnows, leaves etc. into the raw water strainer. I usually back off the throttle to about 1000-1500 rpms for a minute or so and the alarm will go off. There is usually enough water comming in that it allows the engine to cool down enough and not cause any damage. Once the alarm quits is then shut down the engine and immediately inspect the raw water strainer. If there is no water comming in then the problem is the thru hull is blocked. The last time this happened we had sucked up some gravel from the bottom of the harbor from being stuck. I got a piece of stiff wire and cleared the thru hull and we were off again after just a few minutes. If the strainer is not blocked and you are still taking on water, its time to inspect further down the line. Check your belts to make sure that they are not broken or loose. You can actually do this first but my experience has been best starting at one end and working to the other. Then the next item is the impeller. They usually do not completely go away on you, they usually just loose a blade or two. If you back off on the power you can sometimes limp back to the harbor or an anchorage and replace it there. If all of these things check out OKAY, you are then faced with some tougher decisions like the heat exchanger or the elbow and exhaust hose. These are not things that can normally be fixed without being at the dock. The elbow is a good item to have on a every 2-5 year maintenance list. If you have an old one that is in good shape you can have it as a spare and recycle them until one of them corrodes out. If you leave them in for longer than the 2-5 years they normally burn out (especially in salt water) and just need to be replaced.
B
Bryan Cleveland
Shut down on overheat?
I'm not sure it is the best strategy to immediately shutdown if the overheat buzzer rings. You have a hot engine and now stop any water from circulating, which makes it even hotter. If you are getting some water thru the exhaust system, then I'd think it best to throttle back to idle, take the load off the engine, but keep water circulating and see if it cools down a bit before turning off the motor. If you are getting no water thru the exhaust, you have no alternative but to shut her down.
I'm not sure it is the best strategy to immediately shutdown if the overheat buzzer rings. You have a hot engine and now stop any water from circulating, which makes it even hotter. If you are getting some water thru the exhaust system, then I'd think it best to throttle back to idle, take the load off the engine, but keep water circulating and see if it cools down a bit before turning off the motor. If you are getting no water thru the exhaust, you have no alternative but to shut her down.
Bryan that is absolutely correct.
That really is the point. The advantage of the buzzer on the Yanmar panel is the fact that it goes off before you are critical. IF (that is IF) you can determine is you are getting any water thru the system you are better off throttling back. Just as you mentioned the engine will heat even more if the engine has been running for a long time. This is the reason that they really want you to run your engine for several mintues when you return to the dock before shutting it down.
That really is the point. The advantage of the buzzer on the Yanmar panel is the fact that it goes off before you are critical. IF (that is IF) you can determine is you are getting any water thru the system you are better off throttling back. Just as you mentioned the engine will heat even more if the engine has been running for a long time. This is the reason that they really want you to run your engine for several mintues when you return to the dock before shutting it down.
B
Bob F
P
Pete
water temp gauge
Bob, water temp gauge can be installed without too much trouble. Tee into the hot water exchage line and install and sending unit and gauge. (on my 3gm30f I just came off the thermostat houseing with a nipple and a tee) You can still leave the yanmar warning system intact and have a second line of warning. There should be alot of info in the archive about this.
Bob, water temp gauge can be installed without too much trouble. Tee into the hot water exchage line and install and sending unit and gauge. (on my 3gm30f I just came off the thermostat houseing with a nipple and a tee) You can still leave the yanmar warning system intact and have a second line of warning. There should be alot of info in the archive about this.
R
Roy Mosteller
I Installed Gauges
Bob. I put gauges for water temp and oil pressure on the 2GM20F on my 30T. They work great. Since you are in San Diego come and look at my installation.
Bob. I put gauges for water temp and oil pressure on the 2GM20F on my 30T. They work great. Since you are in San Diego come and look at my installation.
D
Don Alexander
A Shaving Mirror, a Stick and a piece of String
Hi all, Some time ago I wrote this for our Legend Owners Association newsletter. It may amuse some folks but recently I found a mirror connected to a car aerial which works just fine. “A SHAVING MIRROR, A STICK AND A PIECE OF STRING” I had a bit of a fright the other day. We were doing compass adjusting and after a couple of hours running back and forth at low engine revs I suddenly noticed that the exhaust noise had changed from the normal gurgle and splosh to a hollow putter putter. To me this indicated a dry exhaust and I was further convinced because there was steam rising from the rear end of the boat. Our 376 has the exhaust outlet underneath the aft overhang of the hull so it is not possible to see whether there is any water coming from it. Very nervously we went back to the mooring to investigate. The seawater strainer was clear and I removed the water injection bend from the engine but that was perfect. Next I took the plate from the water pump but found it impossible to get the impeller out as there was insufficient room. Lord help us when it really does fail! However, using a torch and a mirror, the impeller looked okay. So how was I to check for cooling water. No overheat alarms had gone off, but having been running at little more than idle it was reasonable to suppose the fresh water side of the cooling system was not in distress as it could still have been heating the calorifier and so might not have overheated the engine. After thinking about it I found my small shaving mirror and, using the aforementioned string, tied the mirror to the stick. Then standing on the “patio” I lowered the stick and mirror over the stern slightly to port and, presto, I was easily able to see the exhaust outlet which was gushing with the occasional flush of water. All was well. False alarm. But, unless you are carrying the right equipment, you have no other means of checking the cooling water flow. So you need items not normally found on a cruising yacht; namely:- a shaving mirror, a stick and a piece of string. DA PS: I also carry a small mirror from a birdcage for really tight corners.
Hi all, Some time ago I wrote this for our Legend Owners Association newsletter. It may amuse some folks but recently I found a mirror connected to a car aerial which works just fine. “A SHAVING MIRROR, A STICK AND A PIECE OF STRING” I had a bit of a fright the other day. We were doing compass adjusting and after a couple of hours running back and forth at low engine revs I suddenly noticed that the exhaust noise had changed from the normal gurgle and splosh to a hollow putter putter. To me this indicated a dry exhaust and I was further convinced because there was steam rising from the rear end of the boat. Our 376 has the exhaust outlet underneath the aft overhang of the hull so it is not possible to see whether there is any water coming from it. Very nervously we went back to the mooring to investigate. The seawater strainer was clear and I removed the water injection bend from the engine but that was perfect. Next I took the plate from the water pump but found it impossible to get the impeller out as there was insufficient room. Lord help us when it really does fail! However, using a torch and a mirror, the impeller looked okay. So how was I to check for cooling water. No overheat alarms had gone off, but having been running at little more than idle it was reasonable to suppose the fresh water side of the cooling system was not in distress as it could still have been heating the calorifier and so might not have overheated the engine. After thinking about it I found my small shaving mirror and, using the aforementioned string, tied the mirror to the stick. Then standing on the “patio” I lowered the stick and mirror over the stern slightly to port and, presto, I was easily able to see the exhaust outlet which was gushing with the occasional flush of water. All was well. False alarm. But, unless you are carrying the right equipment, you have no other means of checking the cooling water flow. So you need items not normally found on a cruising yacht; namely:- a shaving mirror, a stick and a piece of string. DA PS: I also carry a small mirror from a birdcage for really tight corners.
J
Jack Beale
The Manual Says
We have the 34 hp (non-turbo) in our 380. The Yanmar manual says that it can be run at 3400 RPM's for an hour without damaging the engine. The manual also says that you can use 3400 RPM's indefinately without harm. I've been using the formula from my piloting days (airplanes) for the power settings on our boat. That is, I've been using 65-80% power for most cruising. Now, I have a question. If 3600 RPM's is 100% power and 1000 RPM's (approximately) is essentially zero power, than the range is 2600 RPM's (3600 - 1000). If you follow this, then 80% power equates to about 3080 RPM's - I usually use 3100. I've cruised at over these settings (3300-3400) for hours on end and have noticed black exhaust covering parts of the swim platform after several days of cruising. This indicates too high a power setting and I've backed off from these settings and have found that 3100 RPM's seems fine. What do the others out there say...?
We have the 34 hp (non-turbo) in our 380. The Yanmar manual says that it can be run at 3400 RPM's for an hour without damaging the engine. The manual also says that you can use 3400 RPM's indefinately without harm. I've been using the formula from my piloting days (airplanes) for the power settings on our boat. That is, I've been using 65-80% power for most cruising. Now, I have a question. If 3600 RPM's is 100% power and 1000 RPM's (approximately) is essentially zero power, than the range is 2600 RPM's (3600 - 1000). If you follow this, then 80% power equates to about 3080 RPM's - I usually use 3100. I've cruised at over these settings (3300-3400) for hours on end and have noticed black exhaust covering parts of the swim platform after several days of cruising. This indicates too high a power setting and I've backed off from these settings and have found that 3100 RPM's seems fine. What do the others out there say...?
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