Well looking into 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!:big_smile:
I have the same size boat. I just upgraded from a 5 hp gamefisher to a 20 hp honda. My max speed with just me (205 lbs.) and light gear in the boat is 26.4 mph, so your estimates appear to be right on. I've been out a couple of times fully loaded down with gear and one other person (240 lbs.) and the boat got on plane just fine, although a bit slower. It sounds like you may go faster considering our weight differences.
I'd say your numbers are pretty close. I've got a 1448 flatbottom jon that weighs 260# empty, 100# motor (25hp), i'm about 250 and fish with someone that is 200. I figure about 50# of gear give or take 10 or 20#. My boat will go about 26 or 27mph by my gps wide open. I cruise about half throttle 22mph. With just me in the boat it'll do about 28 or 29 mph wide open. Your boat should definately plane with 3 people, 4 might be pushing it, but i'd say it probably will.
Hi Folks, Some thing that may help is a sting ray type fin on the bottom of the motor to channel and direct the pushed water, It helps on every boat I have had!
I have a friend that has a 1436 lowe with a 15 hp 4 stroke nissan and it will run 20 on gps with 2 people. They load it down with 4 guys (way overload) small end guy 155 top end 210 and it will still plain out. I have a 1448 lowe with an old 18 hp johnson that runs good and the 15 blows mine away! I am planning to buy a 20hp Tohatsu this month with my tax return. I know this is a late post but if you have aready got yours how do you like it and how fast is it running your boat?
Ryan, your just lucky superman was in the boat with you. A cat that big could probably whip a man in 10 foot of water. LOL
YES! The predictions were RIGHT ON! 27mph by GPS by myself and it was not even topped-out, it would over-rev after that. Easily 22-25 with 3 (140-150lbs) people in the boat. The Tohatsu 20 is a kicka$$ motor, with lots of low-end torque. BIG step-up from the 5-horse. Almost done breaking it in, can only run WOT for a few seconds at a time, and it's more than I care to. I can cruise with a few people around 18-20 at half throttle. The acceleration is abonoxious. I'ma get some pictures of my boat next time I'm about to go fishing....it's a really nice looking rig now with a new aluminum/wood deck!:roll_eyes:
Are you kidding I wasn't in that little ass boat with all of them guys. I was in my big boat and the camera. I will say this, that little boat has seen a lot of big flats though!!!!
