Bf20 issues

My engine failed looks like drive shaft spline is the crank shaft socket replaceable can’t get engine off till next week but looks like this has failed or is the engine worth repairing

I enjoy doing this kind of thing, but not everyone shares that enthusiasm. No experience with the 20's, but if it's like the 40's, there's a counter gear that carries the splines. Splines are not in the crank. Just a gear that you should be able to find used, and does not require you to tear the engine down to replace. Do NOT force the motor apart. It's very easy to miss bolts that must be removed for the motor to release. If you don't have a manual, often the parts books with show a pretty decent drawing showing the locations of all of them.

BF20 splines into the crank, no reduction gear. No insert either, probably not worth fixing unless you can find a good used crankshaft for a reasonable price

Hate to hear that happened! I love the BF20D and have one. They are very rugged and earned my respect when I worked on a rental fleet of them. Hardest service an outboard can do in my opinion. Never saw a failure like that in any of them through hundreds of prop to rocks incidents and collisions while reversing.
They're easy to work on if you can find parts and want to try.
I would.

Agree. I've had a few with the shaft stuck in the crank with corrosion but never seen one let go completely. Pull it apart and assess the situation

ill pull it apart when i get home i am hoping its the drive shaft that failed and the crank is ok i had no warning it went with a few cracks and no drive or water from the pump engine still runs but no drive its the extra long shaft fingers crossed shaft has sheared

Only just got my trailer back engine is extra long shaft the extension piece has a bearing which has overheated and snapped drive shaft ,would a long shaft gearbox fit on if the extension piece was taken off ?a second hand gearbox and crankshaft would be a cheap easy fix has anyone any ideas

The gearbox would be the same and I'm assuming what you're thinking would work.

But...if you're SHORTENING the outboard, how is it going to then fit your boat correctly?

Or, am I misinterpreting what you're considering?