Bobbie, I have a 1984 Trail-Rite trailer for my M-15 too. When I first got the boat I went to the local trailer shop for a drop hitch, they said trailers should tow level. That was 16.5" to the top of the ball in my case. For what it's worth they told me sitting a little higher than level on a single axle trailer wasn't too bad, as compared to too low (untill I got the correct length drop hitch). George