Strengthening a transom.

[fatherfire89]

I am thinking about building a small jet boat but I dont want to spend lots of money and it doesnt need to be pretty. I have my heart set on a 12' aluminum jon boat with an older 60/40 2-stroke jet. I figure any used cheap 12' jon boat I buy isnt going to be able to support a 60/40 2-Stroke while trailering over a bumpy gravel road so I want to strengthen the transom and hull to support it. Maybe run some 1/4" thick angle iron down the sides just below the rails and add a piece of 1 1/2" thick plywood to the transom??? Just thought you guys might have some other suggestions.

Thanks!
-Mark

 

[DrNip]

How much does that engine weigh? Most the 12' jons out there are only 32" & 36" with short sides.

 

[Lil' Blue Rude]

Can't believe I'm the one to say this :roll: but that's gonna be too much motor. I run a built 60/40 omc cut down to a short shaft on a 16' 42" and that's ALOT of motor for that boat. 14' 42" is the smallest I'd run my motor on and that would be a scary ride at that. You might get way with running something like a 40/28 or a 50/35 omc. Plus the boat would be pretty heavy in the rear with a 60/40. I can tell quit a bit of difference with my 60/40 vs how it set with my 40/28.

 

[huntinfool]

I agree.
But if you're set on doing it, I'd take the plywood out and pour a solid glass transom.

 

[huntinfool]

I agree. But if you are dead set on doing it. I'd take the wood transom out and pour a solid glass transom.

 

[loosecaboose]

With that amount of motor weight it will be too heavy in the rear, causing it to draft too deep. Lil blue rude knows what he is talking about, I'd rethink the size of the boat/motor combination.

 

[dhoganjr]

I have to agree with lil blue rude and what everyone else has said, too much motor for that size of boat. With the motor weight, fuel tank, and battery the transom is going to be near the water level. When you steer with a jet, it will tend to push the stern sideways and slide in the turns. That narrow of a boat will dig in, in the turns and the stern will be under the water level. Also if you stop quickly, full throttle to idle, a wall of water will come over the back of the boat and it will take on water at the back of the boat. One good wave and you will be swimming.

My first boat I put together was a 15 36 with a 25/18 and it did the same thing, the extra 3 feet in length helped but it needed a little more width. It worked with a few mods I did to deflect the water but was not near as heavy as a 60/40. Also it did not have enough hp to make it slide as much.

Try to find at least a 14 42. Just my 2 cents worth but it will hopefully save you money in the long run.

I took that boat apart 8 months later and put that motor on my dads 14 50 and had my current boat built.

Good luck with whatever you decide, just be safe!!!

 

[semojetman]

A 12' boat with a 60/40 will end up closer to the fishys than you planned.

 

[fatherfire89]

Thanks for the input guys, I think you are right. I planned on sitting in the front to balance out the boat but I see what you are saying about the boat/transom sitting too low in the water.

 

[DrNip]

Maybe if strengthen the transom and put pods on the back but still it sure would be one scary ride. Then you would still have to worry about water coming over the short sides.

 

[flatboat]

if its a 12 x48 commercial hull [no rating] you could run it on there ,I know guys that run hot 40 merc prop rigs on em . trolling motor on the front and battery up there . I would bring it to a welding shop and let them beef up the transom and raise it . You only live once! Once you mount the motor on there and put it in the water you will know right away if its possible . Please video it so we can see the excitement in your face as you go flying by ! Those ' Oh $hit what was I thinking ' moments are always the best !

 

[user 6672]

flatboat » Today, 05:34[/url]"]if its a 12 x48 commercial hull [no rating] Please video it so we can see the excitement in your face as you go flying by ! Those ' Oh $hit what was I thinking ' moments are always the best !

Please video this if attempted..

 

[smackdaddy53]

I dont see the difference in putting a 60/45 on a 12 footer when there are 17x56 tins with 175hp plus jets on them. Hell, I think I have seen a few 225 mercs hanging off a couple of 18-20 foot hulls on here.

 

[Lil' Blue Rude]

Don't do it! One big difference between the prop and a jet motor is the prop motor has a skeg to ride down in the water when it gets on plane. the faster you go the more the hull picks up out of the water. Smaller hulls gonna come out of the water more which is fine if you have a skeg to set down in the water to keep you going straight but a jet doesn't have that and gets squirrelly when they start picking the boat up.
A 17 56" is still a pretty big hull plus most of them that have bigger motors on them have transoms with more then one knee brace, they are at least .100" gauge and they usually have taller sides then say a 17' 52" that has a 60/40. I'm all for a small boat and a big motor but that's just to much motor for a 12' boat.

 

[dhoganjr]

Yes there is a 250/175 hanging on my 1860 the difference is in the width and side height. Most 12 Footers, (any used cheap 12' jon boat) the op was referring to are narrow with short sides and would have to have the transom and sides raised to avoid water coming over the sides and stern in turns and stopping. A 36" also drafts deeper in the water, and will dig in in the turns causing the stern to be under water. It would be a wild ride that is for sure, but I'm thinking more wet' n wild.

 

[DrNip]

If you are going to do it, do it on a weld craft like my 12'. 24" sides, 21" transom and .1 thick. Mines rated at 30 HP. Good luck finding a used one though.

 

[dhoganjr]

As lilbluerude said my hull is .100" guage, has 3 transom knee braces, 27" transom, and 28"sides. I also ordered it in the commercial model.

I had it built for the 250 from the beginning.

 

[BryantheNurse]

I am thinking about building a small jet boat but I dont want to spend lots of money and it doesnt need to be pretty. I have my heart set on a 12' aluminum jon boat with an older 60/40 2-stroke jet. I figure any used cheap 12' jon boat I buy isnt going to be able to support a 60/40 2-Stroke while trailering over a bumpy gravel road so I want to strengthen the transom and hull to support it. Maybe run some 1/4" thick angle iron down the sides just below the rails and add a piece of 1 1/2" thick plywood to the transom??? Just thought you guys might have some other suggestions.

Thanks!
-Mark

Hi I bought 3/4 I have electrical conduit smashed the ends with a sledge to flatten the end , bent to angle of transom wall and secured to floor brace. Really gave great support to transom wall.Hope this helps ya. BRYAN.

 

[Still Afloat]

Bryan, it’s been 9.5 years since the last post. I would assume the OP moved on to another project or died trying to run a 60/40 on a 12’ Jon.

 

[LaqueRatt]

I would assume the OP moved on to another project or died trying to run a 60/40 on a 12’ Jon.

Is it bad that this made me laugh? I truly hope this isn't the case!