Max hp and small boats

[dirtymike]

I'm curious as to what the limiting factor on small john boats is for the max hp. Is it the weight or just the strength of the transom? I picked up a 25hp real cheap and I want to find a small boat to put it on, around 12-14, so i can have a little boat that will scoot around. The motor isn't that heavy, and with just myself and some fishing rods i don't see how that could hurt. Now transom strength is the one part i could see having an impact on the hp rating, but I can build a reinforcement for it.

Never had a boat smaller than 20 feet, but i want something to get into the shallows when i head out by myself or just the gf and want to save some gas.

 

[NYGiants]

Re: Max hp and small boats

youll need something at least 14' long. look around and themetal plate will tell you max hp and max weight

 

[Home Cookin']

Re: Max hp and small boats

a 25 on a 14' jon (flat) is very fast. It's also a good motor for a 13' whaler or other similar, and heavier, boat.
A great rig for the shallows is a Carolina skiff J series and the 25 will push a 14 fine, even a 16. They are basic, inexpensive and very popular boats, stable and roomy.

Nice thing about a 25 is you don't need to mess with a battery.

You can put a larger motor on a small boat if you use a steering wheel (due to better/safer control).

But always go by the manufacturer's plate and don't exceed it. If you find an old generic boat with no plate, look at a similar newer model for the info--those hulls haven't changed in 50 years. In fact, even if you aren't going to buy new, go window shopping to get an idea of what's out there.

 

[Cannondale]

Re: Max hp and small boats

This is the Coast Guard formula for determining max hp for boats under 20' in length. Note that when determining max hp, the manufacturer is apparently free to state a lower rating if desired, and sometimes does.


(Formula simplified):

(2 X L X W) -90 = rated horsepower

Where:

L=boat length
W=transom width; if the boat does not have a full transom,
the transom width is the broadest beam in the
aftermost quarter length of the boat.

The rated horsepower may be rounded up to the nearest "5".




The above is simplified from here:

http://edocket.access.gpo.gov/cfr_2003/julqtr/33cfr183.53.htm




And remember, it is not a violation of Coast Guard regulations to install or use an engine larger than specified on the capacity label, but there may be state regulations prohibiting it, and restrictions from your own insurance company regarding this.

There is a Coast Guard regulation that gives Coast Guard Boarding Officers the power to terminate the use of a boat (send it back to shore) if, in the judgment of the Boarding Officer, the boat is overloaded.

 

[DuckHunterJon]

Re: Max hp and small boats

Just my opinion, but I think 25 would be too much for a 14' john boat. We used to have a 14' starcraft v bottom, and it would rip with an 18. I can't imagine more motor on it being a good thing.

 

[lckstckn2smknbrls]

Re: Max hp and small boats

I'm running a Mariner 25 hp on a 1436 jon. 14' is as small as I would go it's fast

 

[steelespike]

Re: Max hp and small boats

Here's another thought as far as depth in the water a bare bones 16 or 18 ft utility with a 25 really doesn't use any more water than a 14 and possibly less.They are more stable
both from design and natural weight.They will plane easier and run faster than a smaller boat with a load.You will, feel like your on the Queen Mary compared to a small boat.
I use my 18ft. in the 1000 islands it planed easily with 6 adults and a old gale 25 now run a 50.
Granted you are talking about a 375 lb boat in a 18 footer.

 

[Home Cookin']

Re: Max hp and small boats

agreed about 25 being almost too fast. We had one at our hunt club on a 14' Lowe wide body jon (square bow) and it was scary fast. Since children use it, we went down to a 15 when the 25 died, and it was a good move. So I wouldn't recommend a 25 except for a responsible and experienced operator. Plus good point about weight being in proportion. So since you (OP) have the motor already, step up to 16. But if you find a smaller console boat like a whaler go for it.

 

[dirtymike]

Re: Max hp and small boats

well one of the main reasons i'm sticking to small is that i am in college, and want the cheapest way to get on the water without having to take out my dads boat. If i had the money for a 13ft boston whaler i would have already bought one, but i don't. I don't want to spend more than 800, and there are a few 12 and 14ft boats here for under $300. I found a nice looking semi-v 14ft, but my friends are telling me to stay away from a v and get a regular flat bottom because they are more stable and can take more weight. Is this true?

 

[H20Rat]

Re: Max hp and small boats

This is the Coast Guard formula for determining max hp for boats under 20' in length. Note that when determining max hp, the manufacturer is apparently free to state a lower rating if desired, and sometimes does.


(Formula simplified):

(2 X L X W) -90 = rated horsepower

It should be noted that is an approximate rule of thumb and often wrong. Using that, the max that should be on my boat is ~160 hp (2x16.5x7.5)/90. (might actually be less, I'm being generous with 7.5 beam.) The SMALLEST engine that comes factory equipped is 175hp, the largest is 240hp. (all coast guard certified of course)

 

[lncoop]

Re: Max hp and small boats

well one of the main reasons i'm sticking to small is that i am in college, and want the cheapest way to get on the water without having to take out my dads boat. If i had the money for a 13ft boston whaler i would have already bought one, but i don't. I don't want to spend more than 800, and there are a few 12 and 14ft boats here for under $300. I found a nice looking semi-v 14ft, but my friends are telling me to stay away from a v and get a regular flat bottom because they are more stable and can take more weight. Is this true?

No, it's not true at all, and a semi-V basically is a flatbottom. There are differences, but for most applications they're interchangeable. Semi-V and V hull designs are often incorrectly considered to be the same thing, but they most definitely are not. Since you want to be able to run shallow it sounds like either a semi-V or traditional flatbottom jon boat would be the ticket. That said, if you want to use that 25 you need to look for a 15' minimum length. If you're determined to go 14' or smaller why not consider swapping the 25 for something in the 9.9 to 20 range and a little cash to boot? Not sure where you are, but around here 25s are in demand, so assuming yours is in good condition you might even be able to swap it for a complete rig. I know that would be doable in my neck of the woods. Plus, since you're trying to keep expenses down, think of the fuel economy. You can go a long way with a 9.9 and a five gallon tank of go juice. Think about it partner. More than one way to skin a cat(fish) ya know.

 

[Home Cookin']

Re: Max hp and small boats

I understand about the cost of a whaler; I wasn't suggesting a new or newer one but sometimes you come across old ones, also the clones like McKee are good for what you are looking for. The point is, a heavier boat at 13 will handle your motor better. You would be very happy with a 16' J series Carolina Skiff, too. Just take your time looking around and be ready to jump on something. There is little risk in buying an old hull if it doesn't have flooring. Small trailers are a dime a dozen and easy to fix.
Also keep an eye out for used gear; that gets expensive. Used boat stores, yard and estate sales, are a good way to go. Some marina's have periodic yard sales.
There are a lot of boats still out there that people don't want to mess with over the winter, at least around here (you don;t say where you are located).

 

[steelespike]

Re: Max hp and small boats

Keep in mind there are 14 footers that are what I call small 14s. If you look up new 14s
and check the sizes you will see the difference. The larger boat will plane easier
and run faster with a load all the stuff I talked about.
I kind had a little laugh $800 for a used boat.In 77 my new 18' Crestliner was .995.
about a year later I added a new 77 Merc 500 50hp electrc,tiller for $1500.
Ah well that was a while ago.