Starting a diesel with "dead" batteries

[DDW]

When my starting batteries are dead I wrap a rope around the pulley on the front of the engine and pull. It may work. LMAO

A decade or so ago in one of the sailing around-the-world races, one of the contestants lost his starter motor. They run the engine to charge the battery, need to keep the instruments and autopilot going. To start it, they came up with a scheme involving wrapping a line around the flywheel, running it to the end of the boom, then doing an abrupt jibe. When the boom came across it yanked the line and started the engine (these boats have 1500 sq ft mainsails). Finished the race that way. Hard to duplicate on a trawler though.

 

[KnotYet]

Hand cranking a trawler sized diesel engine without a compression release is likely not possible. Even with a compression release (would a dime under the rocker be enough?) it would be beyond the capability of most, if not all of us.
My own experience, on my 30'sailboat, was with a Yanmar YSE12, a single cylinder diesel WITH a compression release and a properly sized and fitted hand crank. There were a few occasions when I hand cranked that engine, successfully. I was in my 30s and very fit. I wouldn't dream of being capable of hand cranking even that small engine once getting into middle age and later, though I am still fit and weigh close to the same as I did in my 30s. An 80 to 200 hp diesel engine? Not a chance I would even dream of the possibility.

I had the same engine in my 1974 Catalina 30.
The compression release was used every time you started the engine electrically.
It came with a crank but without a hole to insert it through the engine enclosure!
You can be sure I corrected that condition before our 1981 Pacific sail to Hawaii.
The ability to hand crank the engine came in very handy on a number of occasions.

 

[Kurplunk]

Agreed. Let`s ignore syjos.

Thanks your post. It's like that old "S" shaped bent wrench in my toolbox, never used but someday I'll be sure glad I have it - Whether on the boat or on the dirt.
Only a fool scoffs at knowledge.

 

[syjos]

Only a fool scoffs at knowledge.

Only a fool would stick a dime between a valve and rocker without knowing the valve clearance to piston top.

Only a fool would be on a boat with a dead starting battery and no back up starting system.

 

[AdkChris]

My $0.02 more.
Gas engines have spark plug ignition and they will start without high compression. So the compression release in gas engines is designed to reduce the compression ratio but still allow the engine to fire with the compression release engaged.

Diesel aka compression ignition engines need the heat developed by quickly compressing the air in the cylinder to ignite the fuel. The compression release diesel engines I have seen release all the compression to make it easier to spin the engine up to a minimal RPM then the the compression release is deactivated and the engine makes full compression and either starts or coasts to a stop.

With full compression release you would only be working against the internal friction of the engine. From working my way thru college in transmission shops I would say two reasonably fit men might get a broken in 4 or 6 cyl engine spinning a fast as a starter cranks an engine IF you had a good way to apply your effort to the task. I bet ergonomics would be the deciding factor.
Check out this video:

Instead of a compression release I think the driver disengaged the clutch while the wheel was spun up to speed then popped the clutch in high gear.
Kind of a impromptu inertia starter like on the big (gas) WWII aircraft engines.

You can do a lot more with a lot less if you are resourceful and not afraid to get your hands dirty.