My dad has a boat that we used when I was a kid that I’m going to update. It’s a 1236 from sears in about the year 1969. I’m going to put in a couple batteries, add a few lights, new seats, only a trolling motor, and deck a few areas in the boat. I’m also thinking about adding a couple of pontoons for additional buoyancy so my son can come along with us as well. Any of you ever done this? There are tons of videos out there. Just looking for ideas or suggestions on what would be other good ideas.

Too small to be adding 2 deep cycle batteries
and decks and extra stuff.
It'll probably be overloaded with any more
than 2 smallish adults just using paddles.
Unless I'm misinterpreting what this is,
it's a 12 foot long 36 inch wide jon boat that's
probably riveted.
Do yourself a favor and get a bigger better
boat to do all those mods to.
Or at least buy all new high quality PFD's

BTDT

I would agree totaly with Ranger 99.
A 12 x36 Jon is essentially a one man boat with any amount of gear on board, and even then best used in small ponds and lakes.
There are lots of good used boats especially Jon boats, so id be checking those out first.

My Dad has a 1972 Lowe-line 1236 with a 9.9 Evinrude that takes both our fat asses plus a bunch of fishing gear close to 20mph. I wouldn't take it out in the bay on a rough day but for most lakes it does pretty well.

How do you know you're going close to 20 mph?

I've had a 9 9 evinrude
I'd like to see that

I run a 16’ with a 9.9 and with 2 men it’s a barge.

To the OP? I would totally punt on upgrading that. Save the money for a better project/purchase.

Good post.
Unwise to put money into such a project.

GPS. 19 point something.

GPS is the right answer. I don't think I have ever seen a boat speedometer that was accurate.

I think you should take the money and buy a bigger Jon boat. Here is why. I have a 1432 " Johny" I bought for 50 bucks. It is not nearly as sturdy as my new 1436 Tracker. That 4" was a big difference. If you go a bit bigger , you will increase room, and safety. I can take my 5 horse longshaft ( on a shorts haft boat) and it will plane and go about 11 mph. My buddy had a 1448? with a 15 horse and it went 30 mph. A Jon boat is very efficient.

I don’t disagree with you guys. At this point I’m just going to coat the bottom, and I already got the trailer ready to roll. I’m on the lookout for a 16’ aluminum currently. Hopefully I can find one that’s in great shape that is dirty and folks are scared of. I don’t care if it’s ugly, I just need it to be water worthy.

I was kind of shocked it went that fast. It doesn't feel very safe so we rarely go over 15mph. My 1448 with a 25hp 2-cycle gets up 25mph.

My Dad's motor is a late 90's 2-cycle which has a lot more power than his previous 1972 9.5hp Johnson and it's also bigger/heavier. He said they changed the power measurement to be at the prop in that time so the new motors have a lot more.

Remind's me of the day's pre chronograph in shooting. Bullet's were going as fast as the manuals said they were! I got a used John boat about a year and a half ago with a 20hp Honda. Not a clue how fast if goes but I can get around a lake faster than walking! Wish I knew how fast it was going just so I could try trolling, never done much of that. Been looking at GPS speedometer's on Amazon and think for the price I'll get one. Even if it doesn't work they aren't expensive! Kind of like the old reloading manual's; if the GPS say's I'm doing 1 1/2mph then that's got to be what I'm doing!

Just use an app on your phone designed for highways. It’ll tell you what speed you’re traveling.