Originally Posted by CruisinGA
boater8987- I think TRbenj was referring to what I was describing when he said "several inches below transom"
Comparing cav plate vs. hull height gets much trickier on a v-hull (or other complex shape)... Very simple to do on a basic flat bottomed jon boat.
Ive got a small collection of those 74-92 Johnson/Evinrudes... I grew up with a '86 Johnson 9.9 just like the one you have pictured. I threw a 15hp carb on it and it flew... pushed my 12' v-hull 26mph on the GPS. The later 15's (starting around '81) got tuned exhausts in addition to the carb change which made them a little more powerful... but you can add that carb alone and make a big difference. That 9.9 with the 15hp carb ran just as fast as my '80 15hp. I may have a spare 15hp carb from a parts motor (in need of a rebuild, which is super easy)... the prices they fetch on ebay are crazy. Shoot me a PM if youre interested.
Thats a short shaft (15") btw, which is what you need. The way they measure is from the transom mount to the cav plate (not the centerline of the prop, bottom of the keel, or anything else).
My 12' boat is very low freeboard which can be a pain at times, but the very slight rearward mount that the Mini Jacker provides didnt make any difference in that respect (vs. mounted on the transom itself). Ive seen some fancy wood transom reinforcement done that also raised the transom where the engine mounted, but if you need to raise it more than an inch or 2 (and even that may be pushing it) I would opt for a metal jack plate.