Re: Mark 20 won’t spin freely Home › Forum › Ask A Member › Mark 20 won’t spin freely › Re: Mark 20 won’t spin freely ronboonvilleReplies: 83Topics: 56 March 15, 2018 at 11:17 pm #72553 gear case off and that’s where the problem is. The retainer behind the prop is left hand threads, right? I’ll need to make a spanner of some type and also for the impeller.