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Jump start engine battery

Biggles Wader

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Crank handles are designed to disengage from the crank shaft when the engine starts. Sockets aren't, so when the engine starts you could find yourself faced with a drill rotating with the engine, either that or a kick back. In either case, a broken wrist is about the best you could hope for.

In any case, I'd be surprised if a drill had enough torque to rotate a diesel over the compression. The starter motor uses a very large mechanical advantage to turn the engine; I don't know the numbers, but consideration of the relative size of the starter motor pinion and the flywheel suggest something like 20:1. A high revving (in engine terms) electric drill probably lacks the torque.

There's always the Moitessier approach - wrap the main sheet round the fly-wheel and then gybe!
Careful doing that in the marina though! :LOL:
 

HissyFit

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13 Jul 2020
Messages
329
I was forgetting the extra little gadget that puts a freewheel mechanism between the drill shaft and the crankshaft, so that when the engine fires it doesn't take the drill with it. It has been discussed on these fora sometime in the not too distant past.

Something like this.
 
Last edited:

PaulRainbow

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16 May 2016
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Suffolk
I was forgetting the extra little gadget that puts a freewheel mechanism between the drill shaft and the crankshaft, so that when the engine fires it doesn't take the drill with it. It has been discussed on these fora sometime in the not too distant past.

Something like this.
Chances of that working with the OPs engine is precisely zero.
 

HissyFit

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Chances of that working with the OPs engine is precisely zero.
Considering that hand cranking used to be the way that all engines used to be started, I think you need to be a bit more detailed in your rejection of the principle.
 

AntarcticPilot

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Cambridge, UK
Considering that hand cranking used to be the way that all engines used to be started, I think you need to be a bit more detailed in your rejection of the principle.
I gave reasons above - the torque available from a drill is likely to be insufficient to turn a high compression diesel engine over. The video shows it turning over a small generator engine of much lower power and probably lower compression ratio (I guess it's a petrol engine) than most yacht auxiliaries.

And yes, low power diesels can be hand started - been there, done that, We had a Sabb 8hp in my dad's Halcyon 27 - my father, brother and I could all start it by cranking - but only by getting it going as fast as possible with the decompressor engaged, and then drop the decompressor. It needed two people to do it successfully; one to wind the handle and one to work the decompressor lever! And the person winding the handle ended up blowing hard. Your electric drill might work as a substitute for the person cranking, if and only if there was a decompressor - which we've already seen isn't available on the OP's engine.

You couldn't turn the engine fast enough by hand to start it against the normal compression, and that was a small engine designed for hand starting (it did have electric start as well; a Dynastart, ISTR).

It wouldn't work on a lot of later diesels (such as the Volvo 200x series!) a) because of the higher power and b) because of the lack of a flywheel. A very fit and strong person might manage it, but although the design of the 200x series allows for hand starting, it isn't actually fitted to a lot of them (mine included) - the cam shaft is brought out, but the pin to engage the handle isn't present. Again the electric drill MIGHT work on those engines, by getting the engine spinning withthe decompressor engaged and then dropping it. But I wouldn't bet on it unless I got good odds!

Other people have noted that modern diesels aren't usually fitted with a decompressor, so the chances of hand starting them are close to nil, and the same goes for the electric drill.

Historically, large diesels have been started by auxiliary engines or by something like a Coffman starter - basically a shotgun cartridge! However, they weren't started by hand.
 

HissyFit

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329
I gave reasons above -
Yes, you did: very interesting and informative. In principle, though, in my suggestion one electric motor (the starter) would be supplemented by another. Neither would have to be fully capable of the task on its own.
 

PaulRainbow

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I gave reasons above - the torque available from a drill is likely to be insufficient to turn a high compression diesel engine over. The video shows it turning over a small generator engine of much lower power and probably lower compression ratio (I guess it's a petrol engine) than most yacht auxiliaries.

And yes, low power diesels can be hand started - been there, done that, We had a Sabb 8hp in my dad's Halcyon 27 - my father, brother and I could all start it by cranking - but only by getting it going as fast as possible with the decompressor engaged, and then drop the decompressor. It needed two people to do it successfully; one to wind the handle and one to work the decompressor lever! And the person winding the handle ended up blowing hard. Your electric drill might work as a substitute for the person cranking, if and only if there was a decompressor - which we've already seen isn't available on the OP's engine.

You couldn't turn the engine fast enough by hand to start it against the normal compression, and that was a small engine designed for hand starting (it did have electric start as well; a Dynastart, ISTR).

It wouldn't work on a lot of later diesels (such as the Volvo 200x series!) a) because of the higher power and b) because of the lack of a flywheel. A very fit and strong person might manage it, but although the design of the 200x series allows for hand starting, it isn't actually fitted to a lot of them (mine included) - the cam shaft is brought out, but the pin to engage the handle isn't present. Again the electric drill MIGHT work on those engines, by getting the engine spinning withthe decompressor engaged and then dropping it. But I wouldn't bet on it unless I got good odds!

Other people have noted that modern diesels aren't usually fitted with a decompressor, so the chances of hand starting them are close to nil, and the same goes for the electric drill.

Historically, large diesels have been started by auxiliary engines or by something like a Coffman starter - basically a shotgun cartridge! However, they weren't started by hand.
Thanks for saving me some typing Andy (y)
 

Jamie Dundee

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24 Jul 2019
Messages
518
Rather than go all Heath Robinson wouldn’t it be easier to start with a fresh battery then turn the battery switch to the other battery once the engine is running - hopefully to charge the remaining flat battery?
 

penberth3

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9 Jun 2017
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1,311
…..Historically, large diesels have been started by auxiliary engines or by something like a Coffman starter - basically a shotgun cartridge! However, they weren't started by hand.
I've worked with people who hand started lorry engines back in the day, up to Gardner 180 sort of size. Never tried it myself!
 

TernVI

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8 Jul 2020
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1,362
Or borrow his car battery and take it to the boat.
A better ploy would have been to take a boat battery home and charge it, then the OP would have known if the battery was still any good.
Back before we had cheap solar power, we used to take one battery home each time.
 
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