Question on tri-tooning my 1975 20ft flote boat.

[k5guy38]

Ok guys need some advice. I currently have a 1975 harris flote boat 20'. I just bout two 20ft 19" logs from my neghibor. Now I know how I want to mount it to the boat. The question I have is If I keep the 3rd log full length should I mount it even with the other two. Or should I set it back so it sticks out the rear further than the other two. I plan to mount the motor directly to the tube itself.

[PlaynDoc]

Ok guys need some advice. I currently have a 1975 harris flote boat 20'. I just bout two 20ft 19" logs from my neghibor. Now I know how I want to mount it to the boat. The question I have is If I keep the 3rd log full length should I mount it even with the other two. Or should I set it back so it sticks out the rear further than the other two. I plan to mount the motor directly to the tube itself.

I'm certainly no expert in this, and never attempted this... but, there are people here that have, and sure will chime in....

1. 19" diameter pontoons don't seem very large... What size do you have on your boat now? I'm thinking people usually put larger diameter tube in center of boat than on outsides... Maybe I'm wrong?

2. Mounting the motor directed to the tube itself? I'm betting won't work... I'm thinking there's not enough thickness/strength of the log, to weld or bolt on a motor mount... But again, maybe I'm wrong?

I can't wait to follow this discussion..... I wish you luck!

[k5guy38]

It currently has 19" toons. I was hopeing to mount it like the other one I had seen done where it put the center toon 2" lower than the outside toons. I am not really looking to gain speed just looking to get it out the water a lil more. I have the tools and skills to weld aluminum but am not sure of a good design for the mount. I would sure hate to drop the motor in the water

[RonKMiller]

Mounting it lower won't do anything, sorry. Once you are submerged past the diameter (in your case 9.5 inches under the water) you don't gain buoyancy, and in fact the additional weight and drag created by the water now sitting on top of the log will slow you down.

Buoyancy is determined by the width of the log, ie; the amount of water it displaces. You'll certainly gain buoyancy just by mounting an additional log, but there is a weight and drag penalty to pay that may overwhelm your current motor.

When you see new boats with larger diameter center logs the idea is to allow the boat to turn quicker since it forms more of a V shape on plane and tends to lean into the direction you turn.

Here's a good reference chart to get a ballpark idea of how much you can expect to gain:

toon diameters and weight.jpg (86.97 KiB) Viewed 1452 times

[Mrtoler]

The extra 19" tune WILL make your boat float higher and it WILL make it faster not much faster but faster none the less... The reasoning for dropping the center tube a couple inches is to give the v toon effect, and to get it to lean into turns instead of out...if I were you and I didn't care about performance and just wanted to float higher I'd just mount it without dropping 2"s.... The guy that did the tritoon with 19" logs is Shaun (liquid asset) he took a regular transom and notched a hole in the back of the center tube and welded the transom in.. Check out his rebuild for more info!!

[k5guy38]

Yes liquid assets is the one where I got the idea from. I don't really care about a speed gain just looing to raise it up out of the water. It's got a 85 hp Johnson on it. I don't want to sink the transom in the toon I just want to attach it to the rear of the middle toon .

[Mrtoler]

I'm no expert but I have done so much info on this it's crazy. I don't think you can just mount it to the rear of the tube, I think it will not have the prop in deep enough water. Your going to have to build some sort of transom, I wouldn't try to reinvite the wheel myself I'd do something thats been provin to work... Just my .02

[Bamby]

If you have the skills I'm sure it can be done and you could actually pull it off. First you would need to carefully cut off the endcap on the tube, note you will likely re-weld and reuse it as a plug in front of your fabricated transom. Now you need to determine the depth needed for your new transom. Now mark you pontoon something like this: T . Cut the short end of the T down to center and the long end from the back to the short end cut. Now bend both sides straight up to form the sides of your motor transom. Now take the previously cut off end-cap carefully cut and grind as necessary to neatly fit back inside the pontoon and weld it into place, you have now resealed the pontoon. Now on to the rest of the fabrication and hopefully I can explain this in photo's..

Inside rear view of transom

Motor_Jack_Plate.jpg (178.6 KiB) Viewed 1342 times

Pontoon_Rub_Rail.jpg (148.7 KiB) Viewed 1338 times

pontoon_transom.jpg (137.86 KiB) Viewed 1340 times

Third_Pontoon_1.jpg (101.23 KiB) Viewed 1337 times

Well anyway I hope you can see enough angles from the photo's to see how you could pull this off. I may have a couple of more that may be helpful but they'd need to be re-sized for posting here.

[k5guy38]

That's what I was looking for. How do like it ?