i managed to kill a gardner 150, BUT, after the severe bollocking died down, i was informed that a previous driver had seized the motor up by running it with low watere to the isle of skye and back. so really it had been dealt a mortal blow, i just finished it off!
you can wound one by going down hill over running the engine in top, they will drop a valve, i have never done this, but a mate of mine got the sack for doing it twice to 2 different 8lxb’s!