Relocating Pontoon Transom

[VaGent]

I have a 1984 JC 24' pontoon boat rated for a 90 hp engine. The transom is "inset" 45 inches taking away a lot of usable deck space. I plan on using a Johnson 70 hp engine instead of the 90 which I understand is about 50 lbs lighter then a 90 engine. I want to move the transom back so the engine is behind the stern of the boat thereby giving me needed deck space.

I have the aluminum "Z" bar cross members which happen to be heavier then the original ones from the factory & there is plenty of mounting surface to attach them to. I will be adding one (1) additional cross member which will place the transom approximatly 15 inches from the added cross member. By doing this not only will I gain added deck space but the engine will be in "clean" water behind the rear logs. No welding is required as I am setting it up just like the original setup from the factory which is all bolted together.

Can anyone forsee any problems with doing this & if so what problems could I incur? I'm told this should enhance the overall performance as the pontoon will be setup like most of the new pontoons that are being produced now. Other then possibly a balance problem which I can overcome I can't see any problems with doing this project. Any input from more experienced boaters would be apprciated. The relocation of the transom will be 2 feet from where it is now.

 

[5150abf]

Re: Relocating Pontoon Transom

Sounds like you are on it, without pics it is hard to know for sure exactly what you are doing.

Just take into account the tremendous forces placed on the motor pod, if you feel comfortable that you have enough support then you should be fine.

Just moving the pod back one crossmember should n't cause any problems.

 

[VaGent]

Re: Relocating Pontoon Transom

Here is a picture of the transom area. What I am proposing on doingis moving the trnasom back to the end of the motor area by adding one cross member in order to keep the engine supported just as it is now.





Not being an engineer I believe by adding a cross member at the rear area & running it all the way across the logs as it is now & using a 70 hp engine verses a 90 hp, I believe it will work out OK. I am using the same size cross member & bolts to attach it to the logs. The engine will wind up being mounted 13 inches beyond the rear of the pontoon. I will not be removing any of the existing structure.

The way the engine setup is now, the rear fence has to be removed & there is a heavy aluminum cover that also needs to be removed in order to gain any access to the engine for any repairs that might be needed to take place. I am sure I would be charged extra money to have the engine serviced due to having to remove so much in order to get to the engine to start with. By moving the engine back 2 ft, I will gain deck space as well as have complete
access to the engine.

 

[imported_John o]

Re: Relocating Pontoon Transom

If the motor pod in the new location is being supported exactly as it is now (in the current location) you could even stay with a 90 hp motor (or whatever the boat is rated for). The only difference you are going to see is the fore/aft balance of the boat will change towards the aft. Shouldn't be too bad of a problem though

 

[VaGent]

Re: Relocating Pontoon Transom

That is exactly my thinking as well. Because the balance is going to be shifted rearward, by compensating with weight towards the bow I don't think I should have much of a problem with the balance. The engine will be supported exactly as it was originally PLUS I will be adding one extra cross member at the back due to the fact I can't move the existing cross member. This will also put the prop in "cleaner water" & it should perform better from all that I have been told. The prop will wind up about 18 inches behind the logs. It will be set up like the newer JC pontoons that are being made today. I will post pictures of the final setup in a few days. Thanks for the input.

 

[Jeff-in-PA]

Re: Relocating Pontoon Transom

I just took some pictures of the 115 Mercury hanging off the back of my 1993 Starcraft 240 Starfish ( 24' )

Click for really big pictures.






Mine is only set back about 6" at the top. Basically the pivot on the main motor mount is even with the back of the pontoon.

Jeff

 

[VaGent]

Re: Relocating Pontoon Transom

Jeff, thanks for the pics. Your transom is "inset" compared to the way I am going to do mine. Mine will extend beyond the back of the logs approximatly 13 inches. My logs are "U" shaped & by adding two "Z" bar cross members & adding some splash plates I think I will have more then enough structual support for the extended transom. The "Z" bar I found is the exact same height & width as the originals only thicker which makes them stronger. I have found a guy who has plenty of them for sale 25ft long & he cut them for me. There is no welding on my supports now as everything is bolt togther so it should be fairly easy to move & set back up.

The way mine is now the rear fence has to be removed in order to install/remove the engine plus there is a large aluminum/wood cover box on top of the engine now. It is a mightmare trying to gain working space to service the engine. Once I get the transom moved I will post some pics to show what I have accomplished. Thanks for the pics as in my opinion the more ways to see the different setups the better.





You can see how far the engine is recessed now & see the large engine box cover that I will be removing entirely. The rear fence will be moved forward 20 inces to accomodate 2 storage boxes I will be building to house the battery & other "stuff" I will need to carry. The 28 gal. fuel cell will sit in front of the engine along with the water seperator. The steering cable will exit the right rear of the deck trim & the engine cables will come thru the transom. At least that is the way I have it planned out. We "know" how plans sometime don't work out sometimes don't we?

 

[gerg]

Re: Relocating Pontoon Transom

I would think moving the motor back will cause the rear of the boat to set lower and the front higher.(because of the forces of weight and leverage) I couldn't guess how much, and I wouldn't have a clue how to calculate it out though. How would this affect handling? Would you have to change the height of the motor? Prop change? Just some food for thought.

Someone please correct me if I am thinking too much, I have had a few... 6-packs.

 

[VaGent]

Re: Relocating Pontoon Transom

I would think moving the motor back will cause the rear of the boat to set lower and the front higher.(because of the forces of weight and leverage) I couldn't guess how much, and I wouldn't have a clue how to calculate it out though. How would this affect handling? Would you have to change the height of the motor? Prop change? Just some food for thought.

Someone please correct me if I am thinking too much, I have had a few... 6-packs.

As I am not an engineerI have no way of calculating it. I do know that moving it back 24 inches shouldn't make the much of a difference on a 24 ft pontoon boat. As far as balance goes that is just a matter of trial & error. I see no need in chageing either the prop of the height of the motor at this point. I believe by installing a MinnKota trolling motor with a heavy duty battery upfront along with the seats & generator I will be caring along it should balance pretty well & sit in a normal position.

I guess I will find out soon as I added 2 pieces of "Z" bar today running across the logs & have bolted everything back in place. I used heavier "Z" bar then what was origially used so I know the strenth is there for sure.

Pictures below of before & after.

[/ATTACH][/ATTACH]

 

[Cat nip]

I know this is a very old thread, but I am planning on doing the same thing and wondering how it turned out?

 

[jbcurt00]

Closed

Its been over 2 yrs since VaGent logged on to iboats. Which was 4yrs after he last posted to this topic.

He didnt see fit in 4yrs to post his results when he was active, doubt he will after 2 yrs w no acticity at all.

Which is the whole point of the 90day inactivity rule you KNEW about but IGNORED.