New outboard motor...realistic predictions?

[StuBone278]

Well I'm getting the new Tohatsu 20hp 4-stroke within the week for my WeldCraft flatbottom 1432 jonboat. It's all-welded and weighs around 210 pounds empty, and at the moment I have been running a Briggs/Stratton 5hp. By myself I can get it up to around 13mph with light gear, but with more than 2 light people on it it can't even plane.

1). Will it still be realistic to plane with 3 or 4 (~145lb.) guys?

I then found this plane speed calculator. I entered all the weight and hp and speed to get a constant of around 135. According to the calculator, I should be able to get around 25-27mph with the 20hp while by myself. Anyone ever test this calculator to be accurate? What are yall's jonboat constants at?

Thanks!

 

[5150abf]

Re: New outboard motor...realistic predictions?

A fellow catman ,that is a pretty healthy fish in your avatar.
I had a 14' with an old Johnson 10 and it would do pretty good with me and my buddy.
You may hit 25 but that seems alittle optomistic to me with 3 people, have the biggest guy sit in the middle and keep as much weight as possible from mid boat back, the less weight you have in the bow the easier it is to lift.
If it is a new new motor make sure you break it in like they tell you, that should help it to last a little longer.

 

[tashasdaddy]

Re: New outboard motor...realistic predictions?

set up and loaded properly, 4 guys you are going to be pushing it. what weight is the boat rated for? max wt, includes motor and gear plus people.

 

[StuBone278]

Re: New outboard motor...realistic predictions?

The max hp. rating is 20, and weight is 4 people or somewheres around 890 pounds total.

thanks yall