A 20-inch-shaft Engine on a Classic 13

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
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djahncke
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A 20-inch-shaft Engine on a Classic 13

Postby djahncke » Wed Oct 21, 2015 10:20 pm

Due to some winter damage to my outboard done by a nesting mouse, I decided it was time to re-power my classic 13-footer. I wanted an E-TEC 25, but it is not available with power trim and tilt in a 15-inch shaft. I had to modify the transom on my 13 to handle a 20-inch shaft. Fortunately my local Evinrude dealer knew a fiberglass guy that is a perfectionist.

The fiberglass artisan built up the transom to handle the 20-inch shaft. Then when he was done he didn't like the looks of the curved shims that would be required to accommodate the original curve in the transom. So he decided to redo it at his expense! He added a flat pad to match the motor and glassed it in to look as if it was part of the original Boston Whaler design. He even went so far as to redo the hull number on the transom matching the factory original font.

I can't wait to splash the boat a do a sea trial.

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Flat Transom Pad
IMG_20151007_120807995.jpg (88.53 KiB) Viewed 8407 times


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Completed Transom with repainted hull number
IMG_20151007_120743143.jpg (83.71 KiB) Viewed 8407 times


2015-10-13 13.51.20.jpg
New E-TEC mounted on boat.
2015-10-13 13.51.20.jpg (121.32 KiB) Viewed 8407 times

jimh
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Re: 20 inch shaft on a Classic 13

Postby jimh » Wed Oct 21, 2015 11:49 pm

I really like the method Don used to raise the transom height of a classic 13-footer to accommodate outboard engines with 20-inch shaft length. Adding the flat transom insert is a really good idea.

Boston Whaler did that themselves on the 15-foot hull's transom, which is otherwise quite curvy. They put in a flat section just in the center for the outboard engine mounting bracket to bear against. You can see it in this rear view:

Image

I wonder if the original reason for having a curve to the 13-footer transom was to add some strength to the shape. I am not a mechanical engineer, but I think perhaps having some curve to the transom might make it more rigid than a flat plane.

I hope to see that boat at Mullet Lake next season, and take it for a spin, too. Thanks for posting this interesting report on your 13-foot Boston Whaler modification.

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Phil T
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Re: 20 inch shaft on a Classic 13

Postby Phil T » Sat Oct 24, 2015 5:24 pm

Another great refinement.

I would double check the rigging height. The motor looks to be mounted too low. E-TEC's like to be mounted rather high (3 holes up)
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djahncke
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Joined: Fri Oct 09, 2015 6:30 pm

Re: 20 inch shaft on a Classic 13

Postby djahncke » Sat Oct 24, 2015 10:03 pm

I prefer Evinrude for several reasons. Initially it was because I had had such a great experience with the 1978 Evinrude 70-HP engine I bought new on my first whaler (a 15 Sport). That engine is still going strong. I cannot say the same for some of the other outboards I have had.

When I started keeping my boats in the Cheboygan area over 20-years ago I received such great support and service from the local Evinrude dealer (Johnston Marine), that I don't want to go anywhere else.

Phil, I haven't had a chance to sea trial the boat yet. I hope that the weather next week will allow me to do that while I am at the cottage. Thanks for the advice I will certainly pay attention to the height as I "tune in" the setup.