Hand Cranking a Yanmar 2 GM

[Lyle Lunson]

Does anyone know if a Yanmar 2GM can be hand cranked if a battery fails. I have read in many books that there are many diesel engines that can be hand cranked


Thanks

Lyle Lunson
INTREPID 28 #9

[John Vigor]

Lyle, Yanmar does not normally recommend handcranking. These are fast-revving diesels with a fairly light flywheel that does not retain the kind of inertia you need for a 20-to-1 compression ratio.

Older, slow-revving types had very heavy flywheels that you could get moving with a hand crank, and then simply shut down the valve lifter. There was enough inertia in the heavy flywheel to fire the charge in the cylinder. I once had a BMW 12 hp that was a piece of cake to hand start that way. The valve lifter would slowly wind itself down after after five revolutions of the engine, so you could get both hands on the crank and give it an extra whoomph on the fifth turn. Then the lifter would close itself and boom! the engine would start straight away.

I have heard that some people have managed to kickstart the smaller 7.5 hp GM10s, and my mechanic assures me it's theoretically impossible for a diesel to backfire and break your leg (or your wrist), but I'm still skeptical. You can also help a flat battery by handcranking while the starter motor is operating.

If your battery gets flattish, you can still get it to rev the engine quite fast by lifting the exhaust valve, and when it's spinning nicely, just close the valve down, and it should start.

In extremis, if you have two batteries, and they're both quite flat, connect them in series, rather than in parallel as is normal, so they're putting out 24 volts. Use jumper cables if you have them. Your starter motor will be quite suprised. In fact, it will get quite a kick, but it won't be damaged in one brief start.

Finally, if you're sailing fast, put the gear lever in forward and you'll get a bit of help from the propeller--maybe just enough to help the battery do its job.

John Vigor
CD25D "Jabula"



jvigor@qwest.net

[Bob Ohler]

I have been told both stories about hand cranking the Yanmar 1GM... one that it was easy, and the other that it was impossible. From experience, I can tell you that both were accurate. The first time I tried hand cranking the 1GM, it started without a problem. (I may have had an extra pair of hands there to release the compression release on my command.) The second time, I was by my self, and I had no luck whatsoever. It seems to me, that when I would get speed up, I could not manage to release the compression release in time to get the devil running. From my standpoint, I would say that the 1GM will start by hand cranking IF you have an extra pair of hands assisting you. Without the extra assistance, hand cranking could be difficult on the 1GM. I do not have any experience on the 2GM engine.
Bob O.



bobohler@chesapeake.net

[Olli Wendelin]

I use to have a 12 HP Lister which was only hand crank - no starter. The decompression lever was spring loaded. I tied a line to the lever, pulled it out, and stepped on the line. Once I got the engine spinning I lifted my foot and the engine would fire.

I have recently used a line on the decompression lever on my Yanmar YSB12 to help start on a low battery. I could snake the line from the engine compartment, through the cabin, and out into the cockpit in order to turn the key while the lever was pulled.

If you can get a hand crank mechanism for your 2 GM I would install it to reduce your dependence on your batteries.

A buddy of mine had a 67' cement ketch with a large diesel, Detroit I believe. He attached a hydraulic starter opposite the electric starter. If needed he could pump up the hydraulic accumulator with a hand pump, then open a valve and the 300+ HP engine would start like a champ.


Olli Wendelin
BLUE MOON
Charleston, SC



wendelin@spawar.navy.mil