When ever I dunk a engine I try to get off the trigger as fast as I can. But it don't always work. In a worst case not only twisting a crank, but making the cylinder bore oval and destroying the top end. A shear pin will not stop the top end from getting hydro locked. That is from a big gulp of water in the carb. If I twist a crank, it is no big deal. Just put in a new crank. You can buy one for less than $50.00. It is not that much money. Not like a destroyed modded top end. If you cant afford a $50.00 crank, you are in the wrong hobby.

Guess I'll find out after several dunks weather I avoided serious damage. It would take a year of testing and an expense report. Not say it will avoid damage rather keep damages to a minimum. Just trying something to deal with the leading cause of engine failure.

Been doing this for 28 years and telling me it doesn't is work is wrong unless you've been using a key way that shears. Relieving the extra force from the Weight from the flywheel has to make at least a little difference. I know you guys have a lot more run time and experience with hydro locks but using a key that doesn't shear.

Blow away plug, why not. Just takes time and testing.

There are those who try and are successful and those that do as those that are successful.

FYI
key·way
noun
1.
Machinery . a groove in a shaft, the hub of a wheel, etc., for receiving part of a key holding it to another part.
2.
a slot in a lock for receiving and guiding the key.

Years ago we had a discussion on the dock that ran along these lines.Solutions ranged from air boxes to sphincter activated kill switches.

You can run an engine with no key if you tighten the flywheel enough. I've done this in dyno tests of various ignition timings. It's really easy to twist a Zenoah crankshaft, though. I'd be surprised if even no key would save the crankshaft.

Lohring Miller

I appreciate your opinions from experience and I totally agree that when an engine hydro lock damage will be had. I'm getting ready to assemble a 30 with a tk +1.6 crank and possibly a custom syndicate crank on another engine and the plan is to keep them true for as long as possible. If it doesn't work I will not get upset because I tried to prevent damage. It feels worse when you don't try.