One possibility with your engine is to use the decompressors. (ON EDIT after reading what jackdale posted while I was composing my answer: the 2GM20F does have these -- at least mine does)
These are the folded sheetmetal levers at either end of the rocker cover. Push them upright (towards the gearbox) to decompress.
It might be necessary to improvise a link or links, say out of straightened-out wire coathangers, to be able to manipulate them from where you can reach the starter button.
I would decompress both cylinders, spin the starter, then flip one cylinder back onto compression
(probably doing this suddenly would be best, to make best use of the flywheel effect).
I would guess that, unless it's too cold, the engine will run haltingly on once cylinder, given it's effectively the same as a 1GM with a passenger cylinder. Once it is firing more often than missing on that cylinder,either stop cranking and wait until it looks like handling starting the other cylinder, or just keep cranking and add in the second.
I'm guessing the second option would work better if you happened to guess wrong when you picked which cylinder to start first. (eg the injector is in better shape on the second cylinder, unknown and probably unknowable to you)
If the cranking amps are really marginal, a further possibility to ease starting (in conjunction with decompression) is to warm the engine.
You could drain the oil
and warm it in a pot, then replace it. Meanwhile put hot water bottles around the block, or better yet drain the fresh water cooling
circuit, heat the fluid, and replace it (gradually!)
In extremis, If you were prepared to sacrifice the future prospects of your engine, you could use starting aerosol (aka 'ether' or starting fluid). Some say WD40 or CRC sprayed into the air cleaner is better than nothing, but I have no experience and would not try it unless desperate.
Another option is to try and source a hydraulic starter motor
. These have an accumulator to store oil
under pressure, which is provided by a hand pump. The chances of finding one which could be adapted for your engine are probably remote
; a similar effect could presumably be contrived by rigging
up some sort of pedal drive which can be kludged to an alternator
, so you can put some charge into a cranking battery. A fit human can pedal out maybe 30 amps at 12 volts for a while.
Spring starters are available for many modern engines. Unfortunately the only one I'm familiar with does not list your engine. Spring starters Simms, Lucas, CAV mechanical starter motors from Kineteco Home Page
Hand cranking a 2GM
is probably beyond most people. A 1GM is doable, but (for most people) not with the supplied crank handle: generally you need the handle higher off the cabin sole
so you can use your back and leg muscles, not just your arm muscles.
Yanmar (AFAIK) still make a 2GM
, a special build, for the sole reason it can be handcranked, unlike the newer 2YM.
I think it's designated as 2GMY. It's built for commercial shipping
lifeboats, with a higher starting handle on a dedicated layshaft above the engine, chain driving the camshaft.
You could retrofit something along these lines: There's a sheetmetal cap over the end of the camshaft, on the 2GM, onto which you could fit a sprocket. I think you'd want to gear
it down (as Yanmar do on the 2GMY) by using a sprocket maybe twice as big on the layshaft, because the camshaft spins at twice the speed of the crank, and these engines don't have much of a flywheel.
What this means is that unless you're built like an America's Cup grinder, you're not likely to be able to pull it through the compression
stroke when you decompress even one cylinder, if you're at a mechanical disadvantage as you are on the 1GM.
When fitting a hand crank, you must fit a one-way coupling or sprag clutch
or similar to stop the handle spinning when the engine does start. Contrary to what some people tell you, this will not protect you from backfire: safe technique (never straighten arms completely, do not wrap thumb around handle) is the only safeguard here.
What many people don't realise is that a hand crank can be used to assist cranking using the electric
start, and this can be a major help in marginal charge conditions. Every little helps.