HOW FAST SHOULD I GO

[buttonhook]

I have a 28 hp johnson spl on a 1972 magnum 15'-16'(???) tri-hull bass boat (with all the gear, 2 batteries, full tank,full livewell, me, and the wife)it is heavy. and I got 21 mph on the speedo. I'm going to raise the motor as the cav. plate is way too low (long shaft motor on short transom boat. The motor is splashing alot of water back into the boat once on plane. But does that speed seem right? I have a stringray on it with 4" of set back and a jacking plate my prop is 9.25 X 12 alum. Would going to a sst in the same pitch or alum in different pitch help out any? I just put it back in the water after two years! ran 7 mph first time out before the carb work(cleaning). 21 mph after with no other change.

 

[Kenny Bush]

Re: HOW FAST SHOULD I GO

Getting that cavitation plate running in the right position will definitely help, but with 28 hp, your speed will not improve much. A 60 or 70 hp would be a good match for that 16 footer but that is another day........ Sounds like your prop is allready pitched down to compensate for lower HP.

 

[buttonhook]

Re: HOW FAST SHOULD I GO

I would love to have a 60-70 on it but when you pay $150 for a boat motor and trailer you can't be too choosy. Really the prop is just about the highest pitch I can get. A 9.25 X 13 is the only one bigger (that I've seen for this motor)and I have seen them as small as 9 X 7. I was thinking of stepping down a little like a 9.25 X 11 or going with stainless steel in the same pitch any opinions? How high do i need to raise the motor, i.e... even with, 1"-2"above, or 1"-2" below bottom of boat? The bottom of the boat is (nearly) flat at the stern. How much of a difference will it make? and where is the water intake on this motor? anyone know?? I dont want to overheat the motor.