Bought a Toon' and putting my 70hp Johnzuki on it.

[Rancherlee]

I just bought a 20' Kennedy pontoon and its rated for 70hp max. it has Octagon pontoons on it so it has flat bottoms on the tubes and its pretty light at a listed 700# with no motor. Currently its bare with just a captains station and no other seating (the way it came from the factory). I plan on taking my 70hp 4 stroke Johnson off the Lund and using it on the toon' until I come across another used 4 stroke. Currently the motor pushes my 16' boat ~37mph @ 5800 rpm lightly loaded with a 18 pitch stainless prop. I really have NO idea how fast it will push the pontoon and where to start with propping it, I only have 17p and 19p aluminums around which I know will be too steep. Should I start with a 13p or a 15p?

 

[tashasdaddy]

Re: Bought a Toon' and putting my 70hp Johnzuki on it.

you should start with the props you have. find out what the wot rpms, are. then post your prop question with the data you have gotten, in the prop forum.
why buy a prop with out doing the research.

 

[Silvertip]

Re: Bought a Toon' and putting my 70hp Johnzuki on it.

I'm guessing but I think a 13 will be a tad to little pitch and a 15 would be about right. But Tash is right. Run the 17 and see where you are at. I have an 11P on my 18 footer powered by a Suzy 40 and it spins exactly 5800 rpm which is right on the money.

 

[Rancherlee]

Re: Bought a Toon' and putting my 70hp Johnzuki on it.

main reason I was asking is I have a friendly Johnson/Evinrude dealer that will let me take a used prop to try as long as I leave him a good condition prop as a deposit but he is 30 miles away and I don't get over that way often. I think I'll grab a 15p from him to start with. I hoping to get 25+mph out of this setup as my parents had a 20ft. Ercoa (hexagon tubes with flat bottoms) with furniture and a 50hp Yamaha 2 stroke that would go 23mph on gps with 2 people on board.

 

[steelespike]

Re: Bought a Toon' and putting my 70hp Johnzuki on it.

As I understand it most prop the 4 strokes at the top of their rpm rating.
I think your 4 stroke will have trouble with 15 but I guess a 30 mi trip for another prop won't hurt.But that would depend on what you drive.

 

[Rancherlee]

Re: Bought a Toon' and putting my 70hp Johnzuki on it.

you are right on the 4 stroke liking revs. The 17p and 19p I have are factory OMC props that have never been reworked. I could hit the rev limiter on occation with the 17p ~6100rpm and could barely get 5300rpm out of it with the 19p which is 800rpm difference, got lucky an scored a slightly used stainless Turbo 18p cheap which turned a perfect 5700rpm and 3mph faster than either aluminum . Maybe I should try the 13p first then with the toon.

 

[steelespike]

Re: Bought a Toon' and putting my 70hp Johnzuki on it.

Yes the 13 would probably let you operate without worries of lugging just stay within rev limits.with a 15 if it lugs your stuck having to operate at greatly reduced speeds.