Stopping engine

[Paulam]

My 1987 MK 1 36 with Universal Model S 25. I have been turning key off then pulling handle (decompression?) to the left of panel to stop engine.

Now I hear that I should pull handle then turn off key. Which is it?
thanks

 

[Scott T-Bird]

Definitely shut engine down before turning the key. Have you killed the diodes in your alternator yet? You might want to be sure your alternator is putting out now.

 

[kappykaplan]

I don't think it's a decompression handle - rather a fuel stop handle. I have one that I pull, then turn the key off. Any photos of your setup?

 

[jviss]

Definitely shut engine down before turning the key. Have you killed the diodes in your alternator yet? You might want to be sure your alternator is putting out now.

Turning off the key won't fry the diodes, since it will instantly drop the field current, and it doesn't disconnect the load from the alternator. This is commonly done to put smart regulators back to the beginning of the charging phases, e.g., in case you think you need more time on acceptance and it's already switched to float.

 

[Stu Jackson]

The engine is a M25, not S. Don is right about the key. Kappy is right about the handle. Answer is: it doesn't matter.

You can learn a lot about your engine on the TOAD website and here:
Engines 101 - The BIGGEST & BEST collection of M25 Series Universal Engine Information on the Internet, plus some M35, too This includes a link to the Critical Upgrades topic which has more engine information please read it too.

Diesel Engine - c34.org

 

[Paulam]

Thanks all. It does make sense to me to turn key off first. So far I don't have any starting issues. I haven't had the boat that long. But did come with spare alternator. The only reason I referred to the engine as a Model S as this is what it says on owner's manual. I will take a picture tomorrow of panel and post. Thanks again.

 

[RoyS]

In addition to your shut down procedure suggest momentarily revving the engine up to about 2500 RPM just before pulling the stop cable. This will blow any loose carbon out of your cylinders and, more importantly, blow the accumulated sea water out of your exhaust system.

 

[Paulam]

Thanks Roy that makes sense.

 

[Benny17441]

Turning Off the key switch while the engine is still running may damage the diodes in the alternator. Pull the fuel shutoff lever, wait until the engine stops and the Buzzer sounds and then shut Off the key switch.

 

[Paulam]

Thanks so that handle is the fuel shut off. I am going to take a picture and post.
thanks again

 

[jviss]

Turning Off the key switch while the engine is still running may damage the diodes in the alternator.

That is incorrect, at least for most engines. Turning off the key will shut off the regulator, but doesn't disconnect the load (batteries) from the alternator. It's disconnecting the load from the alternator that causes a voltage spike that ruins alternator diodes. So, while switching a conventionally-wired 1-2-BOTH-OFF switch with the engine running can zap an alternator, turning the key switch off will not. Many people turn the key off and back on to put a smart alternator back into it's initial programming state, in the event they want more ACCEPT mode charging than they've gotten. See my previous reply on this.

 

[Paulam]

Thanks - saw someone today at marina - my pull out is a fuel shut off - so shut fuel off then turn key off. As for battery switch its the last thing I do when engine is shut down - turn batteries off. Thanks again. Think I have it now.

 

[Tally Ho]

I was taught to kill the engine first (fuel cutoff cable) and the turn off the key.

I have also done it the other way a few times by accident, with no apparent damage.

I have a Yanmar 2GM20F engine.

Greg

 

[Paulam]

Thanks Tally - I have been doing it the other way for past year and like you no apparent damage. But I think I will do it the other way from now on. Knowing its the fuel shut off does make sense to do that first.

 

[dkinzer]

I was taught to kill the engine first (fuel cutoff cable) and the turn off the key.

On our H41DS the fuel cut-off is by solenoid rather than by a mechanical linkage. If you turn the key to the "OFF" position, pressing the "STOP" button (to attempt to cut off the fuel) does nothing. Short of going to the engine bay to manually cut off the fuel, you must press the "STOP" button first and then turn the key to the "OFF" position.

 

[Tally Ho]

On our H41DS the fuel cut-off is by solenoid rather than by a mechanical linkage. If you turn the key to the "OFF" position, pressing the "STOP" button (to attempt to cut off the fuel) does nothing. Short of going to the engine bay to manually cut off the fuel, you must press the "STOP" button first and then turn the key to the "OFF" position.

Sort of supports what we are saying…kill engine first, the run off the key.

Greg

 

[Paulam]

yes
just down loaded wind indicator app - PredictWind.com looks cool didn't ask me for $$ probably see something on my mastercard

 

[Tally Ho]

yes
just down loaded wind indicator app - PredictWind.com looks cool didn't ask me for $$ probably see something on my mastercard

I use a “free“version…haven’t had to pay for it. Seems pretty comprehensive. I like the daily briefings for a quick summary.

Greg

 

[heritage]

I usually turn the key off first just to avoid the loud noise of the Yanmar panel warning horn sensing that there is no more alternator output. I don't see how this can damage the alternator diodes since the alternator is no longer putting out power. It's when alternator is putting out power and the load is shut off that the diodes can be damaged.

 

[Don S/V ILLusion]

I usually turn the key off first just to avoid the loud noise of the Yanmar panel warning horn sensing that there is no more alternator output. I don't see how this can damage the alternator diodes since the alternator is no longer putting out power. It's when alternator is putting out power and the load is shut off that the diodes can be damaged.

the alt continues to produce power until the engine (and alternator) stops rotating .