Horsepower

[Jontoon27]

I've got a bare bones 1852 flat bottom, looking at a brand new 20hp tohatsu, wondering if it will be enough. I'm going to puta basic floor and a couple benches with storage and that's it. I live on a small river and will just be hauling a couple people and a cooler to the sand bar and boat club. I don't mind spending the money on something bigger but if I can get by for cheaper that's great. Don't need a speed demon but getting on plane and actually being able to make a 2-3 mile trip reasonably would be nice.

 

[b.gagnon]

I would think a 40 would probably get it on plane but a 75-90 would be best... I am assuming the boat will end up weighing 1200-1500lbs. What kind of hull is it?

 

[ondarvr]

What's it rated for, don't drop down much from that.

 

[Jontoon27]

It's aluminum, I looked at brand new boats identical to it and they are rated 20-65 hp. I don't think it's gonna weigh anywhere near 1200 lbs. not sure what it weighs now but I pulled it off the trailer and flipped it over by myself and I'll probably be adding about 3 sheets of plywood including floor and furniture and that will be it.

 

[ondarvr]

There should a plate inside with the hp rating.

 

[Jontoon27]

It's gone, that's why I looked at the tracker and Lowe website

 

[wahlejim]

If you are talking you and a couple of people on board, it probably won't plane out. Reading some reviews around the internet, it appears that aluminum 1852 boats of older years (you didn't mention the year of this boat) seem to be rated up to 90, but that seems overkill according to several posters. The opinion of existing owners of 90s say 75 would be sufficient, and 50hp owners say 50 gets it on plane, but they wish they had more ponies. 75 seems to be ideal. 20 would not suffice for what you are looking to do, especially with a few buddies, a cooler, and a 2 mile trip.

 

[Jontoon27]

I'm no boat genius, that's why I'm here asking questions. But my dad had a 16.5 fairly heavy flat bottom when I was younger and we took it out with 3 people frequently and it planed fine with a 6hp.

 

[Beagleville]

I'm no boat genius, that's why I'm here asking questions. But my dad had a 16.5 fairly heavy flat bottom when I was younger and we took it out with 3 people frequently and it planed fine with a 6hp.

​Far be it from me to put a damper on childhood memories, but I'm having trouble wrapping my mind around that one. One person with a flat bottom and 6 hp, maybe if the weight is distributed perfectly. Three people, I really have my doubts.

 

[Alumarine]

​Far be it from me to put a damper on childhood memories, but I'm having trouble wrapping my mind around that one. One person with a flat bottom and 6 hp, maybe if the weight is distributed perfectly. Three people, I really have my doubts.

I'm with you on that.
I had a light 12 footer with a 6hp as a kid.
2 kids we got up on plane and scooted along quite nicely.
I can't imagine getting 3 adults up on plane with it though.

 

[Texasmark]

I've got a bare bones 1852 flat bottom, looking at a brand new 20hp tohatsu, wondering if it will be enough. I'm going to puta basic floor and a couple benches with storage and that's it. I live on a small river and will just be hauling a couple people and a cooler to the sand bar and boat club. I don't mind spending the money on something bigger but if I can get by for cheaper that's great. Don't need a speed demon but getting on plane and actually being able to make a 2-3 mile trip reasonably would be nice.

If that suits you go for it. I rented such one day and ran a 9.9 McCullough on it. Had plenty of power for fishing and some playing. Johns are easy to plane and with that large of a boat, lots of surface area to plane easily. Ought to zip right along. If bigger suits you go bigger, but don't apologize for a T 20. From what I hear and read T is good engine, made in Japan as I recall who also make/made some engines of the size for Brunswick (Mercury Marine). Sea Rider runs them down in Peru in the Pacific Ocean and apparently loves them......again as I recall from his postings.

 

[Sprig]

An underpowered boat is just plain no fun and 20hp on your boat would be grossly underpowered. 3 guys, a cooler, gas tank and misc. equipment, I hope you like going slow with the bow up in the air. I realize the more horsepower the higher the cost of the engine. So something moderate like 40 to 50 hp should probably be adequate for your purposes. More horsepower would be better but 40 to 50 will likely work for you. If you under power it you will be sorry and you will have wasted a lot of money on a motor that is inadequate for the boat.

 

[Scott Danforth]

jon boats are usually 15" transom. flat bottom and hard chined

using the calculation from CFR 183 ss53

L X W x.5 -15 = HP limit

https://www.gpo.gov/fdsys/pkg/CFR-2002-title33-vol2/xml/CFR-2002-title33-vol2-sec183-53.xml

take your length in feet multiply by the transom width in feet 18*4.5 x.5 -15 = 25hp limit. (remote steering and a taller 20" transom would be rated at a higher value)

your 20hp motor will be fine.

for all you that say putting a 50hp on a Jon boat without a HP placard, need to go back to the boaters safety course and understand the federal law

 

[Silvertip]

3 sheets of plywood and benches easily amounts to another good size adult. See if you can rent/try a 20hp before you buy. I had an old Johnson 10hp on a 20 foot pontoon. Sure it worked but certainly would have liked more power.

 

[Alumarine]

jon boats are usually 15" transom. flat bottom and hard chined

using the calculation from CFR 183 ss53

L X W x.5 -15 = HP limit

https://www.gpo.gov/fdsys/pkg/CFR-2002-title33-vol2/xml/CFR-2002-title33-vol2-sec183-53.xml

take your length in feet multiply by the transom width in feet 18*4.5 x.5 -15 = 25hp limit. (remote steering and a taller 20" transom would be rated at a higher value)

your 20hp motor will be fine.

for all you that say putting a 50hp on a Jon boat without a HP placard, need to go back to the boaters safety course and understand the federal law

While I might agree that your calculations would indicate the limit for a tiller motor is 25hp, that doesn't necessarily mean it will perform well with 3 guys, gear and a plywood floor.