Transom position.

[A.F.C. 8511]

I read a post from a fella on another forum were the guy "VaGent"(much like myself) did a complete rebuild on an older pontoon. The photos of his boat look just like mine. The transom is inset between the 2 "U" shaped logs. I want to extend it out more like modern set ups.

now..... I have a brand new transome rated to 200 hp. Its about 7 inches longer than original. Any educated guessess on how far past flush with rear of logs I should, could, or can go? Gaining 2 solid feet of rear deck space doing this move will be great. And Im remote locating my fuel tank and batteries closer to mid vessel to better distribute weight on the more narrow older logs.
Im looking for clean water for my new Mercury 115 Command Thrust Pro XS to bite into.

Thanks

 

[bansil]

I have wondered the same and researched some

i came to the conclusion with my older and smaller toons, that either adding wt or moving wt further back will only raise front more and then put rear deeper in water creating more drag.

so i plan next year or so to either add a third pontoon that is a foot or so longer or add a mini pontoon with transom built in

i hope this helps (mine sits low)

 

[HotTommy]

I have a 1990s era two log, 24' pontoon boat. It came with a 90 HP outboard that I used for one season (not enough speed for good tubing). I found a used 150 HP engine with a 25" leg that I rebuilt and used for two seasons. Due to the added weight, thrust and torque on the mount, I changed engine pods. I found a used one that was much heftier than the orginal (that already had welds due to cracking). Because the new engine pod is longer and I needed the engine to mount further back so the taller engine would clear the deck above it, I added cross beams between the logs at the back. I used 1/4" thick angle aluminum for the beams. The aft most beam is about six inches forward of the front of the engine.

When the 150 failed, I gave up on old engines and bought a new Mercury 115 CT with 20" leg and mounted it on the new engine pod. I works fine. The rear of the boat sits low at rest, but it levels out nicely at cruising speed.

My advice on mounting your new engine pod is to add cross beams as necessary and have the aft most beam close to the front of the engine. That will assure that the pod is not being supported like a diving board that will flex too much. Try it that way and if you don't like the weight distribution (i.e., too far back), you can always move the engine pod forward during the next down season. ..... BTW, if you place the engine under a deck, remember to leave room above for the engine to rise as it tilts.

 

[A.F.C. 8511]

Here is a picture of the new cross member. It is 1/4 inch thick. It will be mounted at the rear most point on logs. There will be no over head for engine to hit. I just want swim and sun platform.
HotTommy how far back did you move your transom?

 

[ahicks]

I wanted to make room for a rear swim deck when doing a major floor off renovation that included re-powering (90hp Honda) as well. As there was a lot of unused room in front of the railing originally, I moved the entire rail set forward, trading a lot of that forward room for room in back where I wanted it. That worked out REALLY well, but I would caution that we now have to watch the size of people sitting forward. The front of the boat now has little rise as it comes up to speed with a lot of weight up there (a couple of 300 pounders for instance). It stays flat when loaded like that, leaving a concern for stuffing the front end into a large wake. When the bigger foks are moved mid ship or rear, and replaced with average size folk or kids, we're good to go. Normal usage with just a few people (4?) on the boat, there is no issue.

Out of concern for the "diving board" effect an extended transom might leave me with, not to mention flotation height (24" toons), my transom was left about where it was originally, a few inches ahead of the backside of the pontoons. I too added new cross members, especially after seeing the originals had sagged under the weight/torque of the original 50hp. A new back cross member was added as far back as possible without affecting the engine when tilted fully forward.

New decking was installed as far back as the new cross member (adding about 10" to the original length), then extensions were built on each side of the engine extending the floor back on each side to the rear of each 'toon. Permanent ladder was added to the back of the RH 'toon.

This left plenty of room to the rear of the railing for our purposes. The only down side is keeping an eye on who's upfront if you decide you're in a hurry or somebody is game for a tube ride.

Oh, and the 4 stroke Honda is a dream....

 

[HotTommy]

AFC,
As best I recall, I moved the transom back about 6 inches. I only moved it aft to align the control cables and allow the motor to be tilted without interference from the deck and fence. If my goal had been to move it as far aft as possible, I might have gone another 10-12 inches aft.

 

[A.F.C. 8511]

I did some measuring...
my guess will be 15 to 18 inches...
ill keep yall posted.
thank all

 

[Silver Eagle]

It seems to me that if you bought a new motor the people you bought the motor from installed it for you .Those motors aren't light. So I would hope that they set it in the right place. If they didn't take it back and let them do it.