Jack plate setback?

[fuzznuts]

I got a 320lb 140hp johnson going on a 16 foot jon boat. what size setback do i need to get the most out of my combo? is there a thing as to much setback? The transom is getting redone to take the wieght of the johnson.

 

[Skidz]

Re: Jack plate setback?

Ummm, what is the max hp rating for the boat? I'm thinking you may be way, WAY overpowered here.

 

[Bob_VT]

Re: Jack plate setback?

Why a jackplate???? What is the issue? If you are re-doing a transom on an obviously overpowered boat have it done right and no jackplate will be needed. What is the hull brand? Dis you know it can collapse under pressure? Where are you located?

 

[tin]

Re: Jack plate setback?

I got a 320lb 140hp johnson going on a 16 foot jon boat. what size setback do i need to get the most out of my combo? is there a thing as to much setback? The transom is getting redone to take the wieght of the johnson.

I was thinking maybe a spoiler on the front for down force.............

 

[fuzznuts]

Re: Jack plate setback?

its a custom made jon boat

 

[barbosam]

Re: Jack plate setback?

maybe jon boat is not the right description of this boat? A 16' boat would need a beam of at least 7.5' in order to be able to accomodate that much horespower. That's pretty wide for a 16' boat and a jon boat definately would not have a beam this wide. If it is a jon boat thats way too much power. your average 16' runabout would have a max horespower around 100.

What is the beam?

 

[Bob_VT]

Re: Jack plate setback?

The key question is how much boating experience do you have and where are you intending to boat?

 

[Huron Angler]

Re: Jack plate setback?

is there a thing as to much setback?

Too much of anything is bad...so yeah if you set the motor back too much the bow will kick up if someone looks at it the wrong way.

There's no amount of transom that's gonna make it ready for a 140hp on a 16' aluminum boat.

It might sound fun, but that is why insurance rates go up on boats. Be safe.

 

[fuzznuts]

Re: Jack plate setback?

This is my first boat and i am trying to make a river racer jon boat

The key question is how much boating experience do you have and where are you intending to boat?

 

[fuzznuts]

Re: Jack plate setback?

I think it is 60 inch beam

What is the beam?

 

[barbosam]

Re: Jack plate setback?

that gives it an approximate max HP of 70. ((16x5)x2)-90=70. I guess for a race boat your bound to break some rules but that seems crazy. I hope who ever is building this knows what they are doing. I don't think a jack plate would cut it, I think you'd need an outboard bracket with built in floatation just to support the weight of that motor. I don't know, maybe this is outside of my realm, I've never dealt with a race boat but this is definately way outside your normal boat design principals.

I guess that setback of the bracket would have to be based on how much floatation it provides since this is going to be a mjor issue. Your other major issue is that this boat will be a "wheelie" monster. You will want to make sure the mounting surface for the motor is at 16degrees or more so that you can get plenty of negative trim to fight the major bow up trim this engine/boat combo will produce. I'm not sure if you have thought of these issues but if not its food for thought. I guess I don't have a definate answer for you, just think it through, we are all here to answer questions and good luck.

 

[fuzznuts]

Re: Jack plate setback?

what size boat do you think i should run then bc it seems that im a little overboard you seem smarter than me. im just trying to get top mph with the motor i got if theres a faster boat that i should put this motor on then plz let me know.

that gives it an approximate max HP of 70. ((16x5)x2)-90=70. I guess for a race boat your bound to break some rules but that seems crazy. I hope who ever is building this knows what they are doing. I don't think a jack plate would cut it, I think you'd need an outboard bracket with built in floatation just to support the weight of that motor. I don't know, maybe this is outside of my realm, I've never dealt with a race boat but this is definately way outside your normal boat design principals.

I guess that setback of the bracket would have to be based on how much floatation it provides since this is going to be a mjor issue. Your other major issue is that this boat will be a "wheelie" monster. You will want to make sure the mounting surface for the motor is at 16degrees or more so that you can get plenty of negative trim to fight the major bow up trim this engine/boat combo will produce. I'm not sure if you have thought of these issues but if not its food for thought. I guess I don't have a definate answer for you, just think it through, we are all here to answer questions and good luck.

 

[barbosam]

Re: Jack plate setback?

if your looking for maximum speed a bass boat would probably be best or something similar with a relativley flat bottom. Something like an 18footer maybe (this is a good time for one of you bass boat guys to chime in). I don't know how choppy the river you intend to use this in is, but bass boats can get hairy at high speeds in chop, something to think about. If you know you'll be doing high speeds in some good chop than you need a long and narrow deep vee boat. Check the max horsepower rating for the boat, there should be a plate somewhere on every boat listing its capacities. You really should always respect this rating but for a race boat maybe you can cheat a little, but not by much it will effect its handling.

edit: as a basic rule of thumb (very general) the formula for max HP is (length X beam X 2) - 90 = max HP. Again there are a lot of factors but this is a good place to start to get an idea of what kind of horespower a boat can handle.

 

[fuzznuts]

Re: Jack plate setback?

thanks man so a 18 footer then lol is funny how much 2 feet makes a differ.