What does this do?

[IndyIan]

You get it spinning and then pop the compression release. It isn't easy.

Wow, I think I would carry an extra battery, or two...

 

[Patches]

First boat I worked on was a tug built in 1944. It had a Cleveland 12V 278 for a main engine. Cleveland became Detroit Diesel and the 278 means 278 cu. in. per cylinder and this was a v12. This engine had blow down valves on each cylinder that you would open and spin engine to blow out any water or oil that leaked into the cylinder before start. Most engines this size are air start. This one was battery start, had 10 8D batteries. When the batteries started to go bad we would open the blow downs on 10 cylinders and leave 2 shut and start the engine on 2 cylinders. Then we would crawl down each side of the block and close the blow downs while they were spitting burning fuel over your head. Don't think this would be considered a safe labor practice today.

Ya, I'm pretty sure OSHA would have a problem with that method:thumbsdown:

 

[ritcheyvs]

Wow, I think I would carry an extra battery, or two...

I had this backup hand-crank setup on a 12hp Volvo 2-cyl Diesel and later on a Yanmar 8hp 1-cyl Diesel, both in sail boats. These things have big flywheels (needed with so few cylinders) and I believe I was able to get them spinning fast enough to start via the hand crank. Unfortunately,I couldn't maintain that RPM while using one hand to pop the compression release. I do think that they would have started if a crewman with a second set of hands was available to pop the compression release, but I was always alone at the time. By the way, the crank handle is machined like a ratchet so it jumps out of the crankshaft socket as soon as the motor is turning faster than the starter (me in this case). Having said all that, electric starters are a wonderful invention.

 

[SSdoxie]

I had de-compression on an old Kubota and really liked it. It puts less load on the starter because you can get engine spinning to higher RPM before putting compression load on it. Plus allows to spin the engine over for a few seconds to get that cold oil flowing for better lube when it starts.