just attended a marine electronics class. The instructor stated that shutting off the key to the engine does not hurt the engine. It only disables the tach and the alarms but, contrary to popular belief, does not blow out the alternator because, so long as the engine is still running, the alternator is still able to discharge into the batteries. Yet, the boat manual for my Beneteau 321 with a 27 HP Yanmar 3GM30F warns in bold print never to shut off the key without first shutting off the engine. Second, the instructor also said that at dockside, you could start the engine and run it even with shoreside power running and the battery charger working. Yet, the boat manual warns in bold print never to start the Yanmar with the battery charger working. I presume they think it will overload the batteries or do something evil to the alternator. Yet, my instructor said the batteries don't care where they are getting a charge from. If the alternator senses the charger has topped off the battery, the regulator will simply shut off and the alternator will be happy. Any thoughts on these two issues and the different pieces of advice on got on each one? Thanks.
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Go with the owners manuel
With my boat turning off the key doesn't effect the batteries. But turning the battery selector switch to off will blow the alternator. But with so many options for electronics etc I'd go with the manuel unless the dealer said otherwise. Same with the charger. I have started my boat with the charger on with no problem. But I have an old simple diesel. A newer engine might have a computer controlling fuel etc that could be damaged.
With my boat turning off the key doesn't effect the batteries. But turning the battery selector switch to off will blow the alternator. But with so many options for electronics etc I'd go with the manuel unless the dealer said otherwise. Same with the charger. I have started my boat with the charger on with no problem. But I have an old simple diesel. A newer engine might have a computer controlling fuel etc that could be damaged.
two sources of power
There is always the risk that two sources of power will cause current to flow in the ground connection. This is not only bad for all electronics on board, it can, in worst case conditions, be hazardous. Shore power or on board power. Pick one.
There is always the risk that two sources of power will cause current to flow in the ground connection. This is not only bad for all electronics on board, it can, in worst case conditions, be hazardous. Shore power or on board power. Pick one.
Advice
I have done both, accidentally, with no apparent damage. Why take a chance? On my boat, the electric fuel pump gets its power off the switch, so it shuts down with the key off. Starting the engine with the battery charger on will put a large load on the charger and could possibly damage it.
I have done both, accidentally, with no apparent damage. Why take a chance? On my boat, the electric fuel pump gets its power off the switch, so it shuts down with the key off. Starting the engine with the battery charger on will put a large load on the charger and could possibly damage it.
Rick, go with your instructor.
I've had my 3GM30F since '86. I've run the stock alternator and a Balmar in several configurations. No problem ever developed doing what your instructor said. In fact, if you wire your aftermarket alternator with a 'voltage sense' wire like I did, you can even turn off your selector switch while the alternator is charging and not damage it. Manuals like that of your Beneteau are one of my pet peeves. Making a bold statement (in bold print) without a word of explanation, well, it sucks. Oh, check out my web site. I not only rebuilt the electrical system, but the engine too. Nothing to it.
And your battery charger is not going to get hurt if it's on while you start the engine. If you have to crank the engine long enough to damage the charger, your starter motor will go 'nuclear' first.
I've had my 3GM30F since '86. I've run the stock alternator and a Balmar in several configurations. No problem ever developed doing what your instructor said. In fact, if you wire your aftermarket alternator with a 'voltage sense' wire like I did, you can even turn off your selector switch while the alternator is charging and not damage it. Manuals like that of your Beneteau are one of my pet peeves. Making a bold statement (in bold print) without a word of explanation, well, it sucks. Oh, check out my web site. I not only rebuilt the electrical system, but the engine too. Nothing to it.
And your battery charger is not going to get hurt if it's on while you start the engine. If you have to crank the engine long enough to damage the charger, your starter motor will go 'nuclear' first.conservative approach
is to follow the manual. If you explore your system then you may find out the manual is wrong. But I'd check the wiring etc first. Maybe buy your instructor a beer to come out and look at your boat. As far as manuals go I've seen some that were great and some that were useless. But never one that said something in bold print that was wrong.
is to follow the manual. If you explore your system then you may find out the manual is wrong. But I'd check the wiring etc first. Maybe buy your instructor a beer to come out and look at your boat. As far as manuals go I've seen some that were great and some that were useless. But never one that said something in bold print that was wrong.
Summing it Up
Taking into consideration what has been said here this is what you should do. Shut the engine off with the key on unless you want to turn it off first. Turn off your shore power before you start your engine unless you want to leave it on. Isn't it great getting all of this useful information here online?? Paul
Taking into consideration what has been said here this is what you should do. Shut the engine off with the key on unless you want to turn it off first. Turn off your shore power before you start your engine unless you want to leave it on. Isn't it great getting all of this useful information here online?? Paul
Charger
Do you ever plug in the shore power charger when the house batteries are low??? That is definitely more load than starting the engine! And yes, I always shut the key off before killing the diesel.
Do you ever plug in the shore power charger when the house batteries are low??? That is definitely more load than starting the engine! And yes, I always shut the key off before killing the diesel.
I suppose you SHOULD do both..
the ~right~ way, but I and lots of others on here have apparently done both the ~wrong~ way and there doesn't seem to have been any permanent damage, at least that we've heard about so far in 5+ years at HOW. Like everything else, try to develpe good habits, but doing the suppossed ~wrong~ thing doesn't result in a castrophe.
the ~right~ way, but I and lots of others on here have apparently done both the ~wrong~ way and there doesn't seem to have been any permanent damage, at least that we've heard about so far in 5+ years at HOW. Like everything else, try to develpe good habits, but doing the suppossed ~wrong~ thing doesn't result in a castrophe.
conflicting advice
Rick And you thought your instructor vs your manual was conflicting. Geez. Does you engine have a kill switch? I never heard of a diesel that could be turned off by just the key. Maybe I too have an OLD engine. Figure out your wiring to know what's right. Earlier advice about learning what's there, rather than just trusting to "I've heard tell," "someone told me," and all the other wive's tales, should be enough to get you interested enough to learn what you actually hve aboard your boat. Never heard of a charger getting cooked from the engine running. The charger puts out. So does the alternator. Can't go backwards. Only problem would be that if your batteries are full your tach won't work until you hang a load on the batteries. But why would you ever want to start your engine when you're plugged in? Good luck, Stu
Rick And you thought your instructor vs your manual was conflicting. Geez. Does you engine have a kill switch? I never heard of a diesel that could be turned off by just the key. Maybe I too have an OLD engine. Figure out your wiring to know what's right. Earlier advice about learning what's there, rather than just trusting to "I've heard tell," "someone told me," and all the other wive's tales, should be enough to get you interested enough to learn what you actually hve aboard your boat. Never heard of a charger getting cooked from the engine running. The charger puts out. So does the alternator. Can't go backwards. Only problem would be that if your batteries are full your tach won't work until you hang a load on the batteries. But why would you ever want to start your engine when you're plugged in? Good luck, Stu
Yanmar mechanic agrees with the manual.
Rick: Our Yanmar mechanic told us the same thing about turning off the key. Something about the diodes in the alternator. Why not just follow the mfg. recommendations. There must be a reason, otherwise why would the manual and the EXPERTS say the same thing? It is not like they are trying to make money selling you a $6 oil filter when you could buy an inferior product for $2 less <g>.
Rick: Our Yanmar mechanic told us the same thing about turning off the key. Something about the diodes in the alternator. Why not just follow the mfg. recommendations. There must be a reason, otherwise why would the manual and the EXPERTS say the same thing? It is not like they are trying to make money selling you a $6 oil filter when you could buy an inferior product for $2 less <g>.
me too Don.
Don, I too have accidently done both with no damage. Actually, between my wife, crew's and friends we have turned the key off before using the kill switch countless times and started the engine with the shore power still; a) attached b) attached with the 120v breakers on c) battery charger on d) none of the above. The old girl doesn't seem to care less, she just keep on keeping on..... By the way, our H33 has a Westerbeke 21a, not the standard Yanmar.
Don, I too have accidently done both with no damage. Actually, between my wife, crew's and friends we have turned the key off before using the kill switch countless times and started the engine with the shore power still; a) attached b) attached with the 120v breakers on c) battery charger on d) none of the above. The old girl doesn't seem to care less, she just keep on keeping on..... By the way, our H33 has a Westerbeke 21a, not the standard Yanmar.
Steeeve, I thought you loved me
Why the oil filter comment? *o And your expert is confused with which keys or switches are being turned off. One on the source side is the 'ignition key'. Turn that off and the power is removed from the alternator and it can't put out juice. Nothing happens. Two is the receptor of the power. Turn that off without some kind of sensor on the alternator and you will do harm. Once again, Steve, your expert is just saying 'me too, the book must be right for a reason'. Why? There isn't one. Anybody know, or even suspect that they killed an alternator by turning off the key first when shutting down?
Why the oil filter comment? *o And your expert is confused with which keys or switches are being turned off. One on the source side is the 'ignition key'. Turn that off and the power is removed from the alternator and it can't put out juice. Nothing happens. Two is the receptor of the power. Turn that off without some kind of sensor on the alternator and you will do harm. Once again, Steve, your expert is just saying 'me too, the book must be right for a reason'. Why? There isn't one. Anybody know, or even suspect that they killed an alternator by turning off the key first when shutting down?
I got the final answer by calling Beneteau
I called Beneteau and spoke to the service department. They agreed that, in theory, turning off the engine key with the engine still running won't blow out the alternator. It just disables the alarms and tach. However, they have heard of a few cases where they suspect a voltage spike occurred which blew out an alternator diode. Hence, the warning to always shut off the engine before turning off the key. But, in reality, they truly don't have any cases to back it up. Same with the battery charger. They think turning on the engine with the battery charger already going could lead to a spike which hurts the alternator or even the charger. When pressed, however, they don't have any hard proof this has happened and they agreed that it shouldn't really make any difference. The bottom line appears to be that these two bold print cautions in the manual are probably based on some historical aspect of diesels and charging systems which probably no longer make sense today. I don't have any desire to test it and will follow my old habit of shutting off the engine and then turning the key but I'm not going to have a panic attack if I day dream and turn off the key first thinking I'm in my car. As to the battery charger, I agree with the earlier comment that why have it on if you've got the engine running. So, I'll turn it off if I want to start the engine while still connected to shoreside power. But, again, should I forget, I don't think I'll panic and pull the alternator off to take it to the shop for a check. Thanks for all your help, guys. I appreciate the input.
I called Beneteau and spoke to the service department. They agreed that, in theory, turning off the engine key with the engine still running won't blow out the alternator. It just disables the alarms and tach. However, they have heard of a few cases where they suspect a voltage spike occurred which blew out an alternator diode. Hence, the warning to always shut off the engine before turning off the key. But, in reality, they truly don't have any cases to back it up. Same with the battery charger. They think turning on the engine with the battery charger already going could lead to a spike which hurts the alternator or even the charger. When pressed, however, they don't have any hard proof this has happened and they agreed that it shouldn't really make any difference. The bottom line appears to be that these two bold print cautions in the manual are probably based on some historical aspect of diesels and charging systems which probably no longer make sense today. I don't have any desire to test it and will follow my old habit of shutting off the engine and then turning the key but I'm not going to have a panic attack if I day dream and turn off the key first thinking I'm in my car. As to the battery charger, I agree with the earlier comment that why have it on if you've got the engine running. So, I'll turn it off if I want to start the engine while still connected to shoreside power. But, again, should I forget, I don't think I'll panic and pull the alternator off to take it to the shop for a check. Thanks for all your help, guys. I appreciate the input.
Final Answer
Rick Good work, and thanks so much for getting back with the answers. Very helpful The part about "probably based on some historical aspect of diesels and charging systems which probably no longer make sense today" gives me some pause, though. Diesels have been around for quite some time, and so has wiring and alternatops, and, earlier, generators. It all goes back to the way the system is wired, which is pretty much what their answer to you really was. The historical aspects of diesels and charging hasn't changed one itoa in the last 50 years. The only improvements have been in the quality of the equipment (i.e., generators to alternators, smart charging in lieu of ferro resonants,ZapStops for alternators, better batteries, marine grade wiring, etc.) Sure glad you're more comfortable with what system you have. Still would be a good idea to trace it out yourself. Great winter project. Stu
Rick Good work, and thanks so much for getting back with the answers. Very helpful The part about "probably based on some historical aspect of diesels and charging systems which probably no longer make sense today" gives me some pause, though. Diesels have been around for quite some time, and so has wiring and alternatops, and, earlier, generators. It all goes back to the way the system is wired, which is pretty much what their answer to you really was. The historical aspects of diesels and charging hasn't changed one itoa in the last 50 years. The only improvements have been in the quality of the equipment (i.e., generators to alternators, smart charging in lieu of ferro resonants,ZapStops for alternators, better batteries, marine grade wiring, etc.) Sure glad you're more comfortable with what system you have. Still would be a good idea to trace it out yourself. Great winter project. Stu
Rick's instructor is right
just to let you folks know that i have done both on my hunter which has 3gmf20 yanmar. nothing happened anyway. i believe rick's instructor is right right right.
just to let you folks know that i have done both on my hunter which has 3gmf20 yanmar. nothing happened anyway. i believe rick's instructor is right right right.
Possible altrenator damage
Depending on how you boat is wired, if turning off the key doesn't interupt the alternator to battery connection you should be ok. The problem is if you have a battery switch. If you shut off your batteries with the switch and the engine is still running the alternator will see a very large voltage spike and in all likelyhood will destroy the diodes in the alternator
Depending on how you boat is wired, if turning off the key doesn't interupt the alternator to battery connection you should be ok. The problem is if you have a battery switch. If you shut off your batteries with the switch and the engine is still running the alternator will see a very large voltage spike and in all likelyhood will destroy the diodes in the alternator
Some strange behavior with switch
I have a Yanmar 4JH-TE with a solenoid operated engine kill button on the engine panel. Works just fine with the ignition switch on, but if the ignition switch is off and you try to kill the engine, it will slow down until it almost stops then start right up again, and keep on repeating the cycle - it's impossible to stop! Here's my interpretation of what's happening: with the ignition off, the stop solenoid is (somehow) powered by the alternator alone. As the engine slows down the alternator voltage falls until the solenoid releases, and allows the engine to speed up until the voltage closes the solenoid again. And so it goes... I can't visualize how this would happen - I'll have to look at the wiring to see exactly what is going on. The batteries are definitely not disconnected from the alternator by the ignition switch (they're hard wired to the alternator), and the batteries are brand new. Derek
I have a Yanmar 4JH-TE with a solenoid operated engine kill button on the engine panel. Works just fine with the ignition switch on, but if the ignition switch is off and you try to kill the engine, it will slow down until it almost stops then start right up again, and keep on repeating the cycle - it's impossible to stop! Here's my interpretation of what's happening: with the ignition off, the stop solenoid is (somehow) powered by the alternator alone. As the engine slows down the alternator voltage falls until the solenoid releases, and allows the engine to speed up until the voltage closes the solenoid again. And so it goes... I can't visualize how this would happen - I'll have to look at the wiring to see exactly what is going on. The batteries are definitely not disconnected from the alternator by the ignition switch (they're hard wired to the alternator), and the batteries are brand new. Derek
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