old jon boat transom reinforcement

[Mizzie]

Hi everyone,
I have an old jon boat 12 footer that I recently overhauled.. rhino lined it inside and out.. put a carpeted casting deck, floor etc I went all out! I bought a nice little 4hp johnson for it.. its perfect for it pushes it well. my problem is.. it seems the transom definetly could use some reinforcement theres a dent starting to form on the back, the aluminum on this is thin so I'd like to fix it before it becomes a tare!


I put a peice of plywood there the other day it enforced it pretty good but water was coming up and squirting over due to how the plywood was acting in the water I guess... how should I do this? sheet metal, or? I'd rather not put any bolt holes below the water line..


-Mike

 

[Home Cookin']

Re: old jon boat transom reinforcement

two pieces of 3/4" marine plywood INSIDE the transom

 

[Mizzie]

Re: old jon boat transom reinforcement

thanks for your reply.. there actually already is a piece of wood inside the transom it looks "stock" but in good strong shape, the problem is outside the transom, it looks like someone at one time had a motor that was too heavy and it dented/folded the transom a tad.. so it seems that putting it outside would better distribute the weight and take it off the dent.. i hope i explained this good enough to understand. im not much of a computer person haha

 

[5150abf]

Re: old jon boat transom reinforcement

You might get by with a peice of steel or thicker aluminum there if you can find it, you really don't want wood on the outside of the boat.

Check your transom, it may need rebuilt, it should hold a good bit of weight without moving at all, 1/8'' tops, if it goes more than that I would redo it with 2 peices of 3/4'' ply.

 

[lckstckn2smknbrls]

Re: old jon boat transom reinforcement

A piece of 1/2" plywood would be a good idea. Use stainless steel nuts,bolts and washers to mount it to the boat. Remember that Pressure Treated wood is bad on an aluminum boat.

 

[Mizzie]

Re: old jon boat transom reinforcement

Thanks for the replies guys... I'm a little afraid to drill any holes into the boat but I guess i'm going to have to! it's an old boat! I'm unsure of the year but the registration sticker on it when I bought it said 1975! so it's older than that.. but still looks pretty good!

The transom can hold weight without moving, its the little dent in the middle, when I accelerate with my 4hp I can see the dent forming,,it's not major movement but i still don't like it!

why is pressure treated wood bad on a jon boat? is it because of weight issues or?? I just built a marine carpeted floor and casting deck on the boat with plywood that I used deck sealer on and painted over. it seemed to add weight but when it's just me by myself on the boat it rides okay in the water... still a little scary even with nothing in the boat..

new topic but does anyone have any tips on making the boat safer? the top of my transom is only about 3" from the water line with the motor on and me in the back!!(i'm only 165lbs) ,, I was thinking adding 2x4s or 2x2's all the way around to raise the gunwale height but thought the added weight would defeat the purpose...

thanks for the replies guys,

Tight lines,
Mike

 

[ezmobee]

Re: old jon boat transom reinforcement

The new pressure treated eats aluminum.

 

[lncoop]

Re: old jon boat transom reinforcement

Hi Mizzie. I've been doing the jon boat thing for a long time because they make a lot of sense down here. I hate to say it, and someone overrule me if I'm wrong, but your boat sits so low in the water because it's overloaded. All the rhino lining, treated plywood, etc. adds up to quite a bit of weight. By the time you add yourself, your gear and your outboard you've got a pretty good load on a twelve footer. Don't think they're really meant to have a floor and deck. You might try adding some styrofoam under the additions you've made, but I suspect you'll still find yourself low in the water. As for the transom, they just do that over time. You can probably have a welder fix that for not too much denaro. If you do go that route make sure he specializes in aluminum welding. If he doesn't know what he's doing he'll destroy your rig. Tight lines!

 

[ezmobee]

Re: old jon boat transom reinforcement

You might try adding some styrofoam under the additions you've made, but I suspect you'll still find yourself low in the water.

Foam does not add buoyancy. Only displacement of water does. So all that adding foam would do is add even more weight.

 

[tdrudd87]

Re: old jon boat transom reinforcement

You might try adding some styrofoam under the additions you've made, but I suspect you'll still find yourself low in the water.

Adding foam will make it safer if it swamps but will NOT add floatation under normal circumstances. You have to actually increase displacement to make the boat float higher.

Terry

 

[tdrudd87]

Re: old jon boat transom reinforcement

EZ, you beat me to it!

 

[CATransplant]

Re: old jon boat transom reinforcement

Hmm...I'm betting that this is one of those narrow 12' jon boats that seem to be everywhere. The 3" of freeboard you mention is a sure indication that your little jonboat is way overloaded. Those little boats were never intended to have a floor put in them, or much of anything but you, your outboard, your gas tank, and maybe your dog and a little fishing tackle.

The crimp in the transom, too, is probably due to the thin, lightweight construction common in those inexpensive little jons.

You're probably not in the mood to rip out that decking, I suppose. But your boat would be in much better shape, safety-wise if you did. In any case, get as much weight out of the stern as you can. Put your gas tank, tackle box, and anything else you can as far forward as you can. If you have a trolling motor hanging on the transom, get that 40-50 lb battery move forward, too. That'll raise the stern a couple of inches.

Your little boat was designed to be very lightly loaded, and it'll do a lot better if it stays that way. You can stand plenty tall in a jonboat to cast for any fish that swims. The extra 8" won't make any difference. If you put pedestal seats in the boat, that's just more weight. Put a cushion on the original benches.

Right at the center of the transom, inside, should be a brace angling from the middle of the transom to the floor. Is that still there? If not, that's why your transom got a bend in it.

Be safe.

 

[lncoop]

Re: old jon boat transom reinforcement

Thanks for straightening me out regarding the styrofoam. That's the great thing about Iboats; no matter how much you've learned there's always someone available to teach you more:redface:.

 

[12guns]

Re: old jon boat transom reinforcement

I'll throw in my opinion for what it's worth.
I rebuilt my 14" Duracrap "Fisherman" that was my grandpa's from 1977. I had a local welding shop reweld the cracked corners first, then ripped out all the transom wood including the brace. I rebuilt w/ painted treated (i know, don't say it) 3/4" plywood. after it was all bolted in brace and all, I realized that I had a piece of scrap angle iron that fit PERFECTLY! I bolted it through accross the top of the wood just under the top of the transom. Talk about stout! Only problem is that the weak point is still the corners, but w/ my souped up 9.9 I don't have to worry too much. I also keep the weight down to a minimum as it makes a HUGE difference in these little boats. Good luck w/ your project.

 

[Mizzie]

Re: old jon boat transom reinforcement

Thanks for the replies guys! Great forum!

Hmm...I'm betting that this is one of those narrow 12' jon boats that seem to be everywhere. The 3" of freeboard you mention is a sure indication that your little jonboat is way overloaded. Those little boats were never intended to have a floor put in them, or much of anything but you, your outboard, your gas tank, and maybe your dog and a little fishing tackle.

Cat, well haha you're correct it's a little 12' jon boat, it's not as narrow beam wise as some I have seen, which is the reason I picked it up regardless of it's age.. It's still a pretty narrow boat i've seen wider jon boats but I can stand on it and fish and feel pretty stable (nothing compaired to a true bass boat, but it's what I could afford haha). To answer your questions, I took your advice and moved my 6gallon fuel tank forward more. I don't have a trolling motor/battery so that works. My dog, well my dog would probably sink the poor boat (Very food happy 6 year old chocolate lab lol) so he's usualy not aloud!

When I go out 90% of the time it's myself, on occasion i'll bring a buddy of similar weight. I may have exagerated the water to gunwale level in my earlier post (see pictures below) However, when I was on the boat it did feel like 3" haha,, I'm assuming moving the tank forward more helped a bit too thats a good amout of heavy gas! Thanks for the advice!

Hi Mizzie. I've been doing the jon boat thing for a long time because they make a lot of sense down here. I hate to say it, and someone overrule me if I'm wrong, but your boat sits so low in the water because it's overloaded. All the rhino lining, treated plywood, etc. adds up to quite a bit of weight. By the time you add yourself, your gear and your outboard you've got a pretty good load on a twelve footer. Don't think they're really meant to have a floor and deck. You might try adding some styrofoam under the additions you've made

Hey thanks for your reply! Jon boats are definetly good fun! I appreciate your advice about the weight,, The rhino liner spread out over 12' feet I don't believe is the cause of my problems though, I agree it adds weight! I used about half a 20lb can inside and out. My plywood is the ligher grade plywood, I sealed it with a good quality deck sealer, which definetly did weigh the wood down a tad but spread along the whole boat I have about 40 pounds of decking, all which is removable for easier transport.

I agree there are a lot of yahoos who will add things to boats without thinking about weight! I did a lot of 'math' in the building of my deck, I tried to cut down weight as much as possible.. I believe my original post may have made it sound heavier than it actually is haha.. It sits low in the water but I did a run without all the decking and it was maybe if lucky a half an inch differance.

Here's what the boat looks like fully loaded, full 6gallon tank, tackle, small tool box up front with (screw driver/sockets needed for engine repairs on the go) a couple other random doo-dads, don't mind the blanket and water board, I was 'delivering' that to a buddys boat accross the pond! (I know, The boat.. it's not too pretty haha It was my project while my fiancee is pregnant! couldn't afford much more than that!) I'm happy how it came out but after spending all the money I do realize "we're gonna need a bigger boat!" let me know what you guys think, I will reply after this about the transom issue, I don't want to make this one post too long!

A 40' Hatteras it is not! haha but she sure catches me some fish!

-Mike

P.S. I like the styrofoam idea for under the front decking.. definetly going to look into picking some of that up I believe the extra added couple of pounds would be worth it in a case of swamping or leak.

Don't mind the peice of plywood under the hatch, I wasn't finished making the center hatch cross support so I slid that in place. Also, I measured correctly, haha One hatch IS larger than the other by angle, I felt it would be easier to fit my cooler baitwell up front if one of the hatches were a tad bid larger!

 

[Mizzie]

Re: old jon boat transom reinforcement

I went out yesterday by myself without any decking and I couldn't go past half throttle because my transom was bending slightly if I went any faster! I believe it's time for a rebuild before my engine comes flying off.. anyone have any links to a how to on this? I can't lie i'm VERY iffy about drilling any holes below the water line! I believe it will be difficult to seal with gluvix or any other sealent due to the existing rhino liner.. I definetly should have tested the transom before rhino lining, but honestly when you put your own weight on it it doesn't move, when the motor is pushing it from the center, thats when you notice the bending.. I will take a picture of what I mean tomorrow evening so you guys can better understand what I mean.

Also any advice on makingsome sort of sheet metal L brackets to brace to the top of the transom and the rear side gunwales of the boat in place of the original corner supports to better secure?

 

[lckstckn2smknbrls]

Re: old jon boat transom reinforcement

If you seal the bolts below the waterline with 3M 5200 you will be fine.
You should take a look at www.tinboats.net lots of good info.

 

[lncoop]

Re: old jon boat transom reinforcement

. I agree there are a lot of yahoos who will add things to boats without thinking about weight!

Yep. One of those yahoos might even be one posting in this thread LOL! Been there done that as referenced in my posting on CATransplant's "first boat" thread. http://forums.iboats.com/showthread.php?t=394397 As long as you're happy with how the boat performs in the water and believe it's safe that's all that matters. It does sound like you need that brace between the floor and transom though. That will help it remain rigid as intended. It also makes a very handy plug retention device.

 

[Mizzie]

Re: old jon boat transom reinforcement

. I agree there are a lot of yahoos who will add things to boats without thinking about weight!

Yep. One of those yahoos might even be one posting in this thread LOL! Been there done that as referenced in my posting on CATransplant's "first boat" thread. http://forums.iboats.com/showthread.php?t=394397 As long as you're happy with how the boat performs in the water and believe it's safe that's all that matters. It does sound like you need that brace between the floor and transom though. That will help it remain rigid as intended. It also makes a very handy plug retention device.

Haha I hear ya I've had a lot of yahoo experiences when I first got my old 22' searay! Let's just say, The recent addition of the boater safety class that is mandatory in Rhode Island for anyone operating a vessel with a 9.9hp and up engine or PWC is definetly a good thing! I've had to pluck alot of boaters out of the bay, There is always a boater missing or worse.. That's why I moved my operations to fresh water. I've heard one too many distress calls on channel 16 that used to hurt my feelings knowing I couldn't assist.

About the boat,Thanks I believe it performs well for what it is... the weight is evenly distributed and since it's cap rated for 3 persons/gear and I usualy go out solo, it makes sense to me with the added weight. I'd never put 3 people on this boat, I wonder who thought up the numbers on that capacity plate! 2 people is almost overkill on these small boats!

My jon boat seems to be of 1960s era.. there is no brace from the floor to the transom nor are there any signs of one ever existing in that area.. (no rivit holes, or patches) It boggles me why it wouldn't have one because for a jon boat it's pretty ridgid otherwise! I'm wondering exactly how I should make one...

I'm thinking, and please correct me in any wrong sense of what i'm about to type!

Removing current transom wood.. cut to size 2 peices of 3/4" ply as suggested, I'll treat it with deck wood sealer or a sealing paint (any suggestions on which?) I'd also like to make 2 "L" braces alone the gunwale to transom. and for the center transom support I'm thinking either one center or 2 off center pieces of 2x4 or 2x2 screwed together in a L shape, coated in sealer. bolted through the hull twice on the bottom, and twice through the transom.. sort of like an old wooden sailboat, or row boat..

any suggestions on this, or should I go a differant route? I'm a home/garage renovater by trade so the wood working doesn't bother me, It's the fact of sealing the bottom of the boat that scares me! any suggestions on bolt sizes, O-rings, washers?

I greatly appreciate the help thus far, It's so nice out and the lake is calling my name but looks like i'm fishing from shore untill this is fixed, I'm not taking any chances!

Tight lines..
-Mike

 

[Mizzie]

Re: old jon boat transom reinforcement

If you seal the bolts below the waterline with 3M 5200 you will be fine.
You should take a look at www.tinboats.net lots of good info.

I'm going to check lowes for this stuff right now, thanks for the tip!

and i'll definetly check out that website... seems very jon boat friendly haha.

-Mike