So I'm crewing on my friends h30 ('94, I think)and we've finished our sail and are finished tying up at the slip. He goes to shut off the diesel and says "Oops, I have to shut it off on the key first..." I asked him what he meant and he said someone had told him he had been shutting off his diesel incorrectly. that he should shut it off at the key and then pull the kill switch. That brought up a few questions in my head: Is there any difference on how to shut down the diesel ? Don't both turning off the key and pulling the kill switch do the same thing? What exactly is getting shut down? It stops right away so I'm guessing it's probably not interrupting the fuel, so does it shut off the air to the engine? There is no spark plug so I know there is no turning off power? Sorry if this is basic stuff, but my H26 has an outboard and I know little about inboards.
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Charles Duhon
Pull Engine Stop Knob!!!
I have always heard that you MUST pull the engine stop knob and hold it out until the engine stops (shuts off fuel) Then and only then, turn key off. Doing it the other way will damage the alternator. Another interesting fact, if your stop knob ever breaks or the engine keeps running and you can't reach the in-line fuel valve easily, just place a flat object (book, board, pot lid not ever your hand) over the air breather intake and it will shut the engine off! I would only do this in an emergency though. Charles Duhon S/V Artistry
I have always heard that you MUST pull the engine stop knob and hold it out until the engine stops (shuts off fuel) Then and only then, turn key off. Doing it the other way will damage the alternator. Another interesting fact, if your stop knob ever breaks or the engine keeps running and you can't reach the in-line fuel valve easily, just place a flat object (book, board, pot lid not ever your hand) over the air breather intake and it will shut the engine off! I would only do this in an emergency though. Charles Duhon S/V Artistry
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Jim Russell
Charles Speaks the Truth
Follow Charles advice or buy a new alternator. Pull the kill first, then the key. Whoever told your friend otherwise either mis-spoke, or was mis-heard.
Follow Charles advice or buy a new alternator. Pull the kill first, then the key. Whoever told your friend otherwise either mis-spoke, or was mis-heard.
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DICK MCKEE
You guys got me worried
I have shut down both ways, and to date no problems (lucky I guess)...If you shut down with the key off or on how does it damage the alternator?? You should be at idle with the alternator procucing very little , if any, voltage. I just dont want to get unlucky and buy an alternator...
I have shut down both ways, and to date no problems (lucky I guess)...If you shut down with the key off or on how does it damage the alternator?? You should be at idle with the alternator procucing very little , if any, voltage. I just dont want to get unlucky and buy an alternator...
Lucky McKee
Dick: I actually asked the Yanmar guy about this. It has to do with frying the diodes in the alternator. He said that it is a cumlative effect, we have had people aboard that have turned off the key by accident and also have not had any failure. I assume that it the longer you run the engine with key off the worse that it would be. I must assume that if they say not to do it, then we should not.
Dick: I actually asked the Yanmar guy about this. It has to do with frying the diodes in the alternator. He said that it is a cumlative effect, we have had people aboard that have turned off the key by accident and also have not had any failure. I assume that it the longer you run the engine with key off the worse that it would be. I must assume that if they say not to do it, then we should not.
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DICK MCKEE
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Thorp Thomas
"The sky is falling - run for your life
What’s this malarkey you’re trying to feed us? It’s time to reread the manual again… It's "never shut off the battery selector switch while the engine running" that he said.... Check the wiring diagram, the alternator-wiring doses not run through the ignition switch (that’s a misnomer), it's a direct connection to the "battery" selector switch. Or better yet put an amp meter on the line to the battery and see for yourself. Here’s where it really gets complicated the wire doesn’t actually run to the selector switch, it goes to the power feed to the starter solenoid and can get even more complicated with a splitter (for charging more than one bank of batteries at a time). You could run a diesel forever with the ignition switch off and never ruin anything.
What’s this malarkey you’re trying to feed us? It’s time to reread the manual again… It's "never shut off the battery selector switch while the engine running" that he said.... Check the wiring diagram, the alternator-wiring doses not run through the ignition switch (that’s a misnomer), it's a direct connection to the "battery" selector switch. Or better yet put an amp meter on the line to the battery and see for yourself. Here’s where it really gets complicated the wire doesn’t actually run to the selector switch, it goes to the power feed to the starter solenoid and can get even more complicated with a splitter (for charging more than one bank of batteries at a time). You could run a diesel forever with the ignition switch off and never ruin anything.
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Bob Schmit
Soooo....
I look in the photo forum at the wiring diagram for the 97p42 and it doesn't look like the start switch does anything about stopping the diesel. It just powers the starter,alternator,windlass and "alternator"(oh,oh)output... I think I am starting to see the light.Take away the alternator output by shutting off start switch before the alternator stops turning and doesn't that tend to fry the alternator?? It seems like turning the key first would also not stop the engine as it would still be sucking air and fuel which is all the greedy little sucker needs. Thanks for the education, I'll keep it in mind when I win the lottery and get a bigger Hunter.
I look in the photo forum at the wiring diagram for the 97p42 and it doesn't look like the start switch does anything about stopping the diesel. It just powers the starter,alternator,windlass and "alternator"(oh,oh)output... I think I am starting to see the light.Take away the alternator output by shutting off start switch before the alternator stops turning and doesn't that tend to fry the alternator?? It seems like turning the key first would also not stop the engine as it would still be sucking air and fuel which is all the greedy little sucker needs. Thanks for the education, I'll keep it in mind when I win the lottery and get a bigger Hunter.
B.S. by golly I think ya got it.
Bob: As you probably already figured out the diesel does NOT have an ignition system. Diesels run on compression, soooo the only thing that the "ignition" switch does is provide juice to the starter motor. Once a diesel is running it just does it thing. When you want to stop them you need to cut off the fuel supply and they die.
Bob: As you probably already figured out the diesel does NOT have an ignition system. Diesels run on compression, soooo the only thing that the "ignition" switch does is provide juice to the starter motor. Once a diesel is running it just does it thing. When you want to stop them you need to cut off the fuel supply and they die.
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Bob England
Thorp Thomas is right
The "ignition" switch on the control panel supplies power to the panel -- warning lights and buzzer, tachometer -- and allows the starting solenoid to be energized by the pushbutton. The solenoid is really the big switch that connects the batteries to the starter motor. Once the engine is running, you could do without the key switch being on. We all know that diesels don't rely on electrical ignition. (But then no idiot lights, tach, etc.) The thing that will blow the diodes in your alternator is turning the battery selector switch to off while the engine is running. Cutting the electrical load off the alternator causes a big voltage surge that breaks down the semiconductor junctions in the rectifier diodes. Actually, it's more complicted. Some selector switches are "break before make" and on those even turning from battery 1 to battery 2 or "all" can fry the diodes. Most newer switches are make before break, and it is safe to switch batteries (although I never do this -- just chicken!) Some selector switches have a "field disconnect" feature and on those, the voltage that energizes the field winding in the alternator is cut off before the battery connection of broken. With that kind of switch, the alternator stops making electricity a split second before the battery is disconnected, and I think it's even safe to disconnect the batteries with the engine running. But the KISS prinicple says, "never turn the battery selector switch while the engine is running".
The "ignition" switch on the control panel supplies power to the panel -- warning lights and buzzer, tachometer -- and allows the starting solenoid to be energized by the pushbutton. The solenoid is really the big switch that connects the batteries to the starter motor. Once the engine is running, you could do without the key switch being on. We all know that diesels don't rely on electrical ignition. (But then no idiot lights, tach, etc.) The thing that will blow the diodes in your alternator is turning the battery selector switch to off while the engine is running. Cutting the electrical load off the alternator causes a big voltage surge that breaks down the semiconductor junctions in the rectifier diodes. Actually, it's more complicted. Some selector switches are "break before make" and on those even turning from battery 1 to battery 2 or "all" can fry the diodes. Most newer switches are make before break, and it is safe to switch batteries (although I never do this -- just chicken!) Some selector switches have a "field disconnect" feature and on those, the voltage that energizes the field winding in the alternator is cut off before the battery connection of broken. With that kind of switch, the alternator stops making electricity a split second before the battery is disconnected, and I think it's even safe to disconnect the batteries with the engine running. But the KISS prinicple says, "never turn the battery selector switch while the engine is running".
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Bryan C.
Running with key off ok here
On my 3GM30F, I have frequently turned the key off and even taken it out (based on an understanding explained by Bob and Thorp) while motoring and no harm has been done . Never switch battery selector while engine is running just out of practice, even though I believe my alternator output is hardwired into the house bank (as opposed to the selector switch) which would prevent an open circuit.
On my 3GM30F, I have frequently turned the key off and even taken it out (based on an understanding explained by Bob and Thorp) while motoring and no harm has been done . Never switch battery selector while engine is running just out of practice, even though I believe my alternator output is hardwired into the house bank (as opposed to the selector switch) which would prevent an open circuit.
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farnsworth john
combiner
The more modern designs, where the electrical systems are built around inverter/chargers, use a battery combiner rather than battery isolators. On my 410, this combiner selenoid is activated by the "ignition" key. In other words, with the key off, the alternator does not have access to both the house and engine start battery banks. Also, the newer, larger boats tend to have electric kill switches rather than the old pull chokes, and these kill switches simply will not work unless the key is switched on. Turn off the key on my 410 and you've lost the ability to kill the engine short of going below and sabotaging it manually. (My kill switch, by the way, is in the arch, which also happens to be a great place to lean back. More than once I've had a crew member inadvertently kill the engine while loafing.)
The more modern designs, where the electrical systems are built around inverter/chargers, use a battery combiner rather than battery isolators. On my 410, this combiner selenoid is activated by the "ignition" key. In other words, with the key off, the alternator does not have access to both the house and engine start battery banks. Also, the newer, larger boats tend to have electric kill switches rather than the old pull chokes, and these kill switches simply will not work unless the key is switched on. Turn off the key on my 410 and you've lost the ability to kill the engine short of going below and sabotaging it manually. (My kill switch, by the way, is in the arch, which also happens to be a great place to lean back. More than once I've had a crew member inadvertently kill the engine while loafing.)
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farnsworth john
killing a vision
A buddy of mine has a Hunter Vision 36. His boat was at the YC dock during his wedding reception, and he asked our port captain (who happens to own an H380) to run the boat back to his slip after they'd departed on their honeymoon. The port captain used his (ahem) interchangable Yanmar key to start the Vision, but after delivering it back to the slip discovered that he could not stop the engine because the kill choke was inside the companionway, and the hatches were locked. At the point where I was able to stop laughing I supplied a bolt cutter so that we could get the crazy thing stopped. When the honeymooners returned from Hawaii, they were suprised to discover a strange padlock on their boat.
A buddy of mine has a Hunter Vision 36. His boat was at the YC dock during his wedding reception, and he asked our port captain (who happens to own an H380) to run the boat back to his slip after they'd departed on their honeymoon. The port captain used his (ahem) interchangable Yanmar key to start the Vision, but after delivering it back to the slip discovered that he could not stop the engine because the kill choke was inside the companionway, and the hatches were locked. At the point where I was able to stop laughing I supplied a bolt cutter so that we could get the crazy thing stopped. When the honeymooners returned from Hawaii, they were suprised to discover a strange padlock on their boat.
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Jim Russell
So Listen to Yanmar ???
One wonders why we argue with Yanmar. If we are only going sail our own boat and well understand the electrical system in it, that is one thing. However I plan to charter a number of boats and want to get into a routine that won't damage any of them. Hence for me it is well to follow the advice that was given in Steve's message. Let me repeat: This is what Steve said in his message: I (Steve) actually asked the Yanmar guy about this. It has to do with frying the diodes in the alternator. He said that it is a cumlative effect, we have had people aboard that have turned off the key by accident and also have not had any failure. I assume that it the longer you run the engine with key off the worse that it would be. I must assume that if they say not to do it, then we should not.
One wonders why we argue with Yanmar. If we are only going sail our own boat and well understand the electrical system in it, that is one thing. However I plan to charter a number of boats and want to get into a routine that won't damage any of them. Hence for me it is well to follow the advice that was given in Steve's message. Let me repeat: This is what Steve said in his message: I (Steve) actually asked the Yanmar guy about this. It has to do with frying the diodes in the alternator. He said that it is a cumlative effect, we have had people aboard that have turned off the key by accident and also have not had any failure. I assume that it the longer you run the engine with key off the worse that it would be. I must assume that if they say not to do it, then we should not.
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george kornreich
Now, if your engine is a VOLVO....
Sorry to muddy the waters, guys, but my 430 has a Volvo engine rather than a Yanmar, and on the Volvo, the electronic-controlled fuel cutoff is operated by the keyswitch. So for us Volvo-drivers you HAVE TO turn off the key to stop the engine. What they've done to protect the alternator, if anything, is beyond my knowledge.
Sorry to muddy the waters, guys, but my 430 has a Volvo engine rather than a Yanmar, and on the Volvo, the electronic-controlled fuel cutoff is operated by the keyswitch. So for us Volvo-drivers you HAVE TO turn off the key to stop the engine. What they've done to protect the alternator, if anything, is beyond my knowledge.
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Jon Bastien
Move Farnsworth John's 'Vision' post...
...To the 'Funny Sailing Stories' Forum! I think that's a riot! --Jon
...To the 'Funny Sailing Stories' Forum! I think that's a riot! --Jon
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Mickey McHugh
Stopping a Volvo
My 40.5 has a Volvo and like George's 430, it has an electronic-controlled fuel cutoff operated by the keyswitch. The key must be turned past OFF to the KILL position and held there until the engine stops. To protect the alternator, it is always connected to the Engine Start Battery via an ON/OFF selector switch which should always remain on. A second positive lead from the alternator goes to a solenoid that is energized only when the key switch is ON. This solenoid feeds power to the House Battery(s) via a second ON/OFF selector switch that 'could' be turned while the engine is running since the engine battery is still connected. BUT personally, I never turn it OFF, although since it is an A/B switch because I have dual House batteries, I will switch from A to B because it is a Make-before-Break.
My 40.5 has a Volvo and like George's 430, it has an electronic-controlled fuel cutoff operated by the keyswitch. The key must be turned past OFF to the KILL position and held there until the engine stops. To protect the alternator, it is always connected to the Engine Start Battery via an ON/OFF selector switch which should always remain on. A second positive lead from the alternator goes to a solenoid that is energized only when the key switch is ON. This solenoid feeds power to the House Battery(s) via a second ON/OFF selector switch that 'could' be turned while the engine is running since the engine battery is still connected. BUT personally, I never turn it OFF, although since it is an A/B switch because I have dual House batteries, I will switch from A to B because it is a Make-before-Break.
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