I just purchased a 1986 BAHA sport 220 boat with a 1986 Johnson GT 3.8 V8 outboard. What are the good and weak points of these motors, also what causes them to break the prop shafts ?

You have evidence of any sort of propensity for breaking propshafts? Is this a question or a statement? Just curious as I spent some time on the internet and see nothing regarding this...

I replied on your thread on scream and fly (as Instigator) which is your best shot for OB help.

Doing 20 posts all over ain’t the way to get help.

They aren’t known for breaking propshafts.

If I understand correctly, you just bought it, never ran it, know nothing about the hull, the motor, their history or OBs in general ???

is that the old V8?

Yep

Seen a few powerheads with turbos in sand cars
Looked pretty cool

Propshafts I have not broken, but clamp brackets and one midsection. Pinion gears yes. If the engine has the original lower unit it will have a four hole water pickup rather than the later scoop style. The early units had a smaller diameter propshaft near the thrust washer, it also requires a different thrust washer. That version should also have the big bore carburetor bodies. The emulsion tubes break down in them. The float bowls will warp when they are not torqued properly. They also use Posi Drive screws not Phillips. Flywheel magnets and voltage regulators. I have not blown up any of my powerheads to date. I also run the VRO pumps on all my V8 outboards. Upper motor mounts take a beating.