Raising 15-inch Transon on Older 13-footer

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cjohnsen89
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Raising 15-inch Transon on Older 13-footer

Postby cjohnsen89 » Fri Apr 10, 2020 11:49 am

I am refurbishing a 13-footer that has the original notched transom for a 15-inch-shaft engine. I will be putting on a new Yamaha F25 which weighs 126-lbs.

Shoud the transom be kept at original height?

Should a Kent Fab insert be used to raise the height for a 20-inch-shaft ehgine?

jimh
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Re: Raising 15-inch Transon on Older 13-footer

Postby jimh » Fri Apr 10, 2020 12:43 pm

If the new engine has a 20-inch-shaft height, the engine won't work well if mounted directly to a 15-inch transom.

To get a better answer, tell us the shaft length of the new engine.

See:

CETACEA Page 56.

--and--

A 20-inch-shaft Engine on a Classic 13
http://continuouswave.com/forum/viewtopic.php?t=64

ConB
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Re: Raising 15-inch Transon on Older 13-footer

Postby ConB » Fri Apr 10, 2020 1:36 pm

Here is another choice.

https://www.nausetmarine.com/shop/boston-whaler-transom-riser/

I copied Don Jahncke’s transom raise job on my 13-footer. It takes more time and skill than one would think.

Makes the Kent and Nauset parts look like a good choice.

Con
!987 Outrage 18 / 2011 Yamaha F150
1969 13 / 30hp Johnson tiller

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Phil T
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Re: Raising 15-inch Transon on Older 13-footer

Postby Phil T » Fri Apr 10, 2020 2:33 pm

If you must install a 20" shaft, consider using this. Many owners have installed them.

https://thmarinesupplies.com/products/cmc-static-jack-plate-5-inch-vertical-extension
1992 Outrage 17
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cjohnsen89
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Re: Raising 15-inch Transon on Older 13-footer

Postby cjohnsen89 » Fri Apr 10, 2020 2:36 pm

I can buy either a 15-inch or 20-inch shaft engine.

Are there are any advantages to spending money to raise the transom?

Should I just keep the boat as-is with 15-inch transom?

ConB
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Re: Raising 15-inch Transon on Older 13-footer

Postby ConB » Fri Apr 10, 2020 4:26 pm

I raised mine because I was going to put a power tilt and trim motor on the boat. Most of those are 20”.

If you can buy a 15” motor I would not raise the transom. Just come off plan slower so as not to get pooped by the wake.

Con
!987 Outrage 18 / 2011 Yamaha F150
1969 13 / 30hp Johnson tiller

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Phil T
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Re: Raising 15-inch Transon on Older 13-footer

Postby Phil T » Fri Apr 10, 2020 5:02 pm

Agree with Con.

Don't go to the hassle of band-aiding the transom due to selecting the wrong shaft engine.
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opencage
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Re: Raising 15-inch Transon on Older 13-footer

Postby opencage » Fri Apr 10, 2020 5:32 pm

I went with the Koski mahogany transom extension http://www.koskiboatworks.com/custom-whaler-accessories.html

Haven't put it on yet, I've grossly underestimated the amount of time to do the repairs I need to do. I thought it looked the best, helped prevent wake coming over, weighed the least, and theoretically you can go back to the original notch if you wanted.

jimh
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Re: Raising 15-inch Transon on Older 13-footer

Postby jimh » Fri Apr 10, 2020 9:30 pm

cjohnsen89 wrote:Are there are any advantages to spending money to raise the transom?


I really do not know how to answer the actual question asked regarding what is the advantage of spending money, except in a general answer that spending money is usually good if it gets something you need (or think you need) or makes you happy, and it often allows you to avoid doing a lot of lousy work that you do not enjoy.

Instead I will answer as if you asked this question: Is there an advantage to a higher transom?

You can make a very reasonable assumption that there MUST be an advantage a higher transom just on the basis that Boston Whaler made the transom higher in later models of the 13-footer.

I can think of two advantages: a higher transom will create higher freeboard at the stern. A higher transom will also be stronger than the notched transom.

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Re: Raising 15-inch Transon on Older 13-footer

Postby biggiefl » Mon Apr 13, 2020 11:33 am

Simple...if you want PTnT, you will need to put a 20" engine on it, you chose what method you want. I personally think a standard manual jackplate is the most efficient and strongest and the setback gives you better performance. You can usually bolt these to the original holes, thus not having to drill new ones. If you do not want PTnT, buy a 15" engine and call it a day...a cheaper day.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).