What's this crank?

[Bigjim]

I have a 2QM20 Yanmar. The engine came with this crank. At first, I thought the crank was a hand starter for the engine, but when I turn the crank it only turns the gear and chain on the front of the engine but it does not turn the engine itself.

Does anyone know what this crank is actually doing?

[skipperpete]

Great question. I don’t know the answer but here are a few observations.
Originally the 2QM’s had the crank on the end of the camshaft so hand cranking was anti clockwise as per your crank handle BUT it’s possible that when the gear driven water pump">raw water pump was introduced, another gear was installed for the crank handle and if this ran off the cam gear it would change the hand crank rotation to clockwise ( viewed from the front). Naturally there should be a ratchet and pawls on that later addition to avoid the thing remaining engaged while the engine was running so the problem could be as simple as...... you have the 2QM 15 crank!

[GordMay]

Yanmar 2QM20 “Hand Starting Mechanism”
➥ https://yanmarshop.com/en-GB/catalog...ting-mechanism

[skipperpete]

I actually found a video of a guy manually cranking your model engine clockwise so it seems that the problem is that you have the wrong crank handle.

[Bigjim]

Originally Posted by skipperpete

I actually found a video of a guy manually cranking your model engine clockwise so it seems that the problem is that you have the wrong crank handle.

The handle I have is designed to crank only counter clockwise. It grabs the teeth on the cam when turning that way and slips off when turning clockwise.

[Bigjim]

Originally Posted by skipperpete

I actually found a video of a guy manually cranking your model engine clockwise so it seems that the problem is that you have the wrong crank handle.

Can you paste the link to the video in a comment?

[skipperpete]

See if this works https://youtu.be/vkjOtcARfII?si=aN1uHjiSY4e7NkcK

[skipperpete]

Nope, that failed … so google or search YouTube for “ 2QM20H crank start”, ….bald mechanic with a blue yanmar on first start after workshop rebuild.

[skipperpete]

You might also have a buggered sprag clutch inside the timing gear …. In the parts price list that is an expensive bit of metal.

[Bigjim]

Originally Posted by skipperpete

See if this works https://youtu.be/vkjOtcARfII?si=aN1uHjiSY4e7NkcK

That video is great. There must be a switch somewhere to engage the engine to that crank. My crank is designed to turn counterclockwise.

[skipperpete]

Have you tried to turn the chain wheel in the opposite direction to what your crank handle requires?
Get a pipe wrench and give er a try

[n5ama]

Originally Posted by skipperpete

See if this works https://youtu.be/vkjOtcARfII?si=aN1uHjiSY4e7NkcK

I would have never believed you could start a diesel engine (even a small one) with a hand crank. Compression firing requires very high pressure in the combustion chamber and pulling through that compression stroke is tough.

My Yanmar has a crank but I thought it was no more useful than turning the engine over to facilitate service.

I’m impressed that the little bald headed guy can start his engine by hand so quickly. I wonder if the engine was at operating temperature before he used the crank?

Have a great week,
Tom

[Fintry]

Originally Posted by n5ama

I would have never believed you could start a diesel engine (even a small one) with a hand crank. Compression firing requires very high pressure in the combustion chamber and pulling through that compression stroke is tough.
Tom

Some Yanmars have a compression release, so you can release pressure on one or more cylinders and get the thing spinning, then shut the valve and hope. I've never had a Yanmar with one, but the 60hp Gardner we put in Fintry to run the hydraulics had one for each cylinder.


Jim

[PineyWoodsPete]

Originally Posted by Fintry

Some Yanmars have a compression release, so you can release pressure on one or more cylinders and get the thing spinning, then shut the valve and hope. I've never had a Yanmar with one, but the 60hp Gardner we put in Fintry to run the hydraulics had one for each cylinder.


Jim

Bingo! The Yanmar 2-cyl in our '77 Endeavour 32 had a crank AND a compression-release lever that must be opened first to get the engine spinning with the crank, as shown in the video, then closed quickly as shown to let the mass momentum continue to turn with compression and start.
Pete

[sinnerman]

My boat in Brazil had a two banger diesel also made in Brazil. Sea water cooled.

It had a hand crank as well which I used often as the boat had only one battery which would often be too weak to crank the engine after running the lights.

Added a quick squirt of wd-40 to the air intake to kick it over (not wise, but it worked..)

cheers