The legality of increasing the HP capacity on a boat.

bassindude · May 08, 2012, 08:30:57 PM

I have been thinking about getting a very large Jon boat and building it into a decent bass rig. The one Im looking at is nearly 20ft and 84" wide. It has a max capacity of 60HP, which seems much lower than many boats that are smaller. Im assuming that the other boats have sufficient additional flotation to carry a larger motor, so Im wondering if anyone knows if I can legally add flotation to a boat and increase the HP capacity? And how would I go about getting Legal permition to do this. I know how to add the flotation with the 2 part expandable foam, so thats not an issue, and im sure if you run the numbers on the hulll it could handle the motor size wise, but the label has the 60 HP restriction. Any help would be appreciated, Jim

bigjim5589 · May 08, 2012, 08:58:04 PM

You would likely have to have it approved by the US Coast Guard. Although I'm not sure what you're proposing really changes the specs of the HP rating. That would likely have to be determined by the design of the boat as to whether or not it would handle the stresses of more HP. Hull material thickness & type of aluminum, bracing patterns & such would all have to be considered. Even though you would be adding additional flotation, you would also be adding additional weight, and with a bigger engine, even more weight. So, another consideration would be net weight capacity. Depending on the capacity rating now, you may end up with a loss in net carrying capacity by adding the additional weight. Lots of things that have to be considered.

All of that would have to be proven out by the engineering. Unless you're a registered engineer, or are willing to hire one who can work up the numbers for the changed design and can prove the numbers, I doubt the C.G. would even consider it.

Mike Cork · May 08, 2012, 10:54:35 PM

Bigjim is correct in that the coast guard makes the determinations. Boat manufacturers have to get the Coast Guard to set the limit. Talking with Legend Boats, it's a pretty complicated formula but also basically a math equation. I don't know if the coast guard would issue a new placard to an individual?

But I do know that a couple members here on the site work for the coast guard in different capacities. Spetro can issue safety inspections and may know the process here or point you in the right direction. Shoot him a PM. He loves to help when he can! He's also over the safety board here on the site

PD Fisher · May 09, 2012, 02:49:41 AM

If your still looking for a boat. Check on a commercial rated vessel. They don't have restrictions like that. They are also bare bones which may be what your looking for since you want to do a project turning it into a bass rig. Also more often than not there cheaper than other aluminum boats

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BOATS · May 09, 2012, 04:41:02 PM

This pamphlet from the USCG might help a little, did not read the whole thing but it explains alot

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bassindude · May 09, 2012, 07:45:28 PM

Wow, that was quick. Thanks for the info. I kind of felt that it was probably un-do-able. Definately will get with Steve, if i decide to procede. Im also interested in the Commercial boat Idea. Where would I get more info on who makes commercial boats, Just google it? Jim

PD Fisher · May 10, 2012, 12:24:04 AM

Most aluminum boat companys like (ex. Alumiweld, sea ark) have a commercial line. Some may not. Id search the internet of aluminum boat manufactures, then there web site would list commercial boats if they make them

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bassindude · May 10, 2012, 06:56:31 PM

Thanks PD

PD Fisher · May 10, 2012, 11:52:24 PM

I did a little looking. Check out alweld boats web site. They list commercial and even show the swamp people show as using there boats. Maybe that'll help get ya started.

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boohya1 · June 04, 2012, 11:54:03 AM

I'm taking a 16' thats only has a 36-40" bottom and widinging it to 58-60" bottom. Since I will be doing everything my self I was wondering if I would have a motor restriction? Kind of like making your own boat.

ozarkbilly · June 27, 2012, 04:20:13 PM

Unless you currently have a larger motor, would it may be more cost effective to sell / trade in yours and buy another boat. That being said two things come to mind. 1 older boats and motors had a different hp rating than newer boats have, could be the coast Guard have re-rated your 20ft Jon boat. 2. A friend of mine here in the Ozarks is a jet ski mechanic. He took a V bottom aluminum boat and put a 100 hp jet ski engine in it [a water rocket]. The Mo. Water Patrol [Coast Guard Certified] inspected the boat and approved it. So I suppose your project could happen.