Originally Posted by jyasaki
For what reasoning?
If you drive a boat with even 1/4 or 1/2 throttle and back off power quickly the OB will swing up (due the drag on the prop through the water) ....if you then need to put power on again there is a huge BANG as it smacks back down against the transom ....repeat this a few times and it all goes silent as the engine falls off......and stuff breaks....
Thats before you get to the point of the prop coming clear of the water if pressing on in rough water etc......its a whole lot of movement that is bad news
Very small OBs dont tend to suffer this but anything more than about 10hp shoud have a down lock of some type in my experiance (even it if has finite point of failiure to protect from collision- but even then they dont really 'give' much - they just break...)