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  1. #1
    Petty Officer 2nd Class
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    Default Transom raising questions

    I have a 16 ft jon boat that I use for bowfishing. I need a bigger motor but cant find many that will fit my short 15" transom. I have found enough good deals on long shaft motors that I have decided to raise my transom. I had one guy on a forum tell me that he sandwiched a piece of thick steel between two pieces of 5/8 plywood and bolted it on, and it holds up a 55 horse motor great. I want to put a 40 horse on there and think that this holds up to my skill level

    A few questions about it

    How thick of steel should I use?

    Will I need to use aluminum bolts to prevent the boat reacting with steel bolts?

    Should I bolt the plate to the outside or inside of the boats transom?

    Does it need to go over both sides of the transom?



    OOOOOR

    I buy one of these
    http://www.iboats.com/Transom-Elevat...-view_id.40157

    One question, do I need to drill the holes to mount it?

    Will it spread out the weight enough to not stress the transom?

    Does it need a lip on top of the mount to prevent my motor from sliding off?

  2. #2
    Admiral
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    Default Re: Transom raising questions

    Skip the steel.

    There are a couple of ways to do it.

    You can cut two pieces of aluminum and sandwich a piece of plywood, the aluminum will also sandwich the existing transom and extend down at last 6 inches.


    Or you can have someone fabricate a riser from aluminum and either weld or bolt it place.

  3. #3
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    Default Re: Transom raising questions

    The only reason I was leaning to steel is because I am not sure where I can get aluminum without having to buy a whole sheet, the place I go to now will just use their huge shears and cut me off what I need.

  4. #4
    Lieutenant Commander Lion hunter's Avatar
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    Default Re: Transom raising questions

    Need an idea of what size motor your going to use. The plywood sandwiched between aluminum is best. Steel will work but I would paint heavily (maybe bedliner stuff) with something so that it does not contact the aluminum.
    The Crestliner Restoration

    http://forums.iboats.com/showthread....49#post2218249

    1967 16' Crestliner and 60hp Johnny

    Klamath Trailorboat and 9.9 Johnny

  5. #5
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    Default Re: Transom raising questions

    Probably 40 horse, I wasnt planning on having the steel touching the boat if I could help it.

  6. #6
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    Default Re: Transom raising questions

    Quote Originally Posted by crablegs View Post
    The only reason I was leaning to steel is because I am not sure where I can get aluminum without having to buy a whole sheet, the place I go to now will just use their huge shears and cut me off what I need.
    If they won't cut the pieces then find another place to by it, its very easy to find a place to buy aluminum cut to the size you want.

  7. #7
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    Default Re: Transom raising questions

    So would it be better to have two pieces of aluminum with plywood in between? or the other way around

    What kind of design should I go for, a piece of aluminum that slips over the front of the transom, plywood next, then aluminum that slips over the back of the transom?

  8. #8
    Chief Petty Officer ddrieck's Avatar
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    Default Re: Transom raising questions

    You can use this style outboard lift. It is made specifically for what you want to do.

    http://www.dhcampingandfishingsupply.com/50012.html

    Regards,

    ''Fish Me Gone''



    Democracy will cease to exist when you take away from those who are willing to work and give it to those who are not......Thomas Jefferson





    Find out how you can help prevent the spread of Zebra mussels.
    http://wgfd.wyo.gov/web2011/fishing-1000206.aspx

  9. #9
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    Default Re: Transom raising questions

    Would that spread the weight around enough on the transom? The outboard is a bolt on that Im looking at, would the holes match up?

  10. #10
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    Default Re: Transom raising questions

    There should be a plate attached to the boat that will tell what the HP rating for the hull. What doe it say the MAX HP is?

    As for will your transom be strong enough to hold the raised O/B without more support....we have no idea, you haven't told us the brand, model or age of the boat, or the brand, year and model of 40HP motor you're looking at.

  11. #11
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    Default Re: Transom raising questions

    Its a polarkraft 1652 jon boat, older hull, early 70's I think. Im not sure where the plate is on it, but if I use the length x width -90 and divided by 2 (along the lines of that) it comes to 50 horsepower.

    The motor Im looking at is a 40 merc

  12. #12
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    Default Re: Transom raising questions

    Gee, How about bolting two pieces of heavy angle iron to the transom, sticking up. Now bolt a piece of 2X6 pressure treated lumber or two 3/4" plywood pieces flush with the existing transom. That should hold a 40 HP motor.

  13. #13

    Default Re: Transom raising questions

    I had the same trouble your having. Here`s what I did and it works great. Only down fall is it weigh`s about 15lbs. I took some 1 1/2 square tubing cut it 13" long that`s how long my transom is. I needed to raise mine 7" so I went up seven inches with the tubing and welded all the tubing together. Took some 1/8" steel diamond plate and cut it 13"x 12" and welded that to the tubing. So from the top of the tubing it goes down 12" I have a 4" over hang on the transom that I drilled four holes in and put 3/8" bolts through. Painted it with rhino lining type stuff so it doesn`t rust. It works great for me. I looked into this for a month or so at all the jack plates and didn`t like any of them. I took this to the fab shop and he knew exactly what I wanted as he had just finished another one. If you have any questions I can send you all the specs just pm me. Hope this helps.

  14. #14
    Lieutenant Commander Lion hunter's Avatar
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    Default Re: Transom raising questions

    On a 40hp motor I would use 1/2" bolts. You almost double the bolt strength from 3/8" to 1/2"
    The Crestliner Restoration

    http://forums.iboats.com/showthread....49#post2218249

    1967 16' Crestliner and 60hp Johnny

    Klamath Trailorboat and 9.9 Johnny

  15. #15
    Petty Officer 2nd Class
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    Default Re: Transom raising questions

    Quote Originally Posted by rjn cajun View Post
    I had the same trouble your having. Here`s what I did and it works great. Only down fall is it weigh`s about 15lbs. I took some 1 1/2 square tubing cut it 13" long that`s how long my transom is. I needed to raise mine 7" so I went up seven inches with the tubing and welded all the tubing together. Took some 1/8" steel diamond plate and cut it 13"x 12" and welded that to the tubing. So from the top of the tubing it goes down 12" I have a 4" over hang on the transom that I drilled four holes in and put 3/8" bolts through. Painted it with rhino lining type stuff so it doesn`t rust. It works great for me. I looked into this for a month or so at all the jack plates and didn`t like any of them. I took this to the fab shop and he knew exactly what I wanted as he had just finished another one. If you have any questions I can send you all the specs just pm me. Hope this helps.
    You got any pictures?

  16. #16

    Default Re: Transom raising questions

    I can take some if you want them. Just pm me your e-mail and I will send them to you. I have no idea how to retreive them and post them on here.

  17. #17
    Moderator ezmobee's Avatar
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    Default Re: Transom raising questions

    Check the bottom of this thread for a homemade jack plate idea. That's the route I'd take.
    1976 18' Starcraft SuperSport 90HP Evinrude
    Restoration thread http://forums.iboats.com/boat-restoration-building-hull-repair/18-starcraft-supersport-restoration-357767.html
    1966 16' Starcraft Jupiter 85HP Johnson
    Restoration thread http://forums.iboats.com/starcraft-boats/ezmobees-1966-jupiter-338633.html sold

  18. #18

    Default Re: Transom raising questions

    Question for Tashasdaddy or other, i to have a long shaft motor, 1991 Johnson 40hp. I have a 1996 Generation 3 16 ft john. guage is .062. It is rated for a 35, but kinda hard to find that. Anyway,bought a long shaft, good deal,runs great,but water comes over transom after planing . My question is, if I put an elevator on(similar to what is here,angle(4pcs)with treated 2x6 on transom top., and have a pc of angle welded from the transon to the rear seat back, will this be enough support. I had a freind that had a similar boat with a long shaft 25hp Yamaha, his boat was a 70's model though, and he recently had to redo his transom, as he said he thought that the mototr being 5: higher, plus age severly weakened it.
    Any thoughts? I realize I need a short shaft, but don" have cash, and this motor runs good.

    Thanks in advance, Dave

  19. #19
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    Default Re: Transom raising questions

    I have a 16' G3 at my dock right now, it has a Yamaha 60 jet, which is about 40hp at the pump. I don't have any problem with water coming over the transom, but I see how it may happen.

    Don't use PT wood, it doesn't like aluminum and will win in a disagreement.

    I get all my aluminum at a local salvage yard, they have a great deal of aluminum to choose from, even bent into many interesting shapes. You should be able to find some channel or angle to make a riser to mount the motor too, then use a thin piece of sheet cut to the correct height (about 5") and full width of the transom, if the top is bent it looks and works better. I've found bends like this at the scrap yard, it sells for the same price as everything else, so you don't pay for the bending.

    Another boat at my place has the same support that extends to the seat you asked about, it works well on that boat, but if you have a tiller the supports may get in the way of your feet or legs.

  20. #20

    Default Re: Transom raising questions

    thanks, ondarvr! My boat is alot older and riveted, the newer G3's are all welded, i believe.

    Dave.....

  21. #21
    Chief Petty Officer
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    Default Re: Transom raising questions

    Pressure treated wood and steel,both aren't good with aluminum.
    Try stainless bolts,regular wood(water treated/resin) and aluminum.

    I have know idea what your transom looks like now.
    What shape is it in,wheither theres rot or if it's all aluminum...
    It may need some more bracing down to the floor or corners.

  22. #22

    Default Re: Transom raising questions

    Right now my transom is in great shape, just trying to make sure it stays this way, i realize i could sell this motor and find a short shaft. , but it runs great and i have had to much bad luck buying someone elses trouble........

    Dave

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