13-footer Transom Reinforcement

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
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13-footer Transom Reinforcement

Postby NewEnglandWhaler » Tue Jun 05, 2018 1:41 pm

I am currently restoring a 1968 13-footer. The engine is an Evinrude 40-HP short-shaft. Being a rounded transom, I know I need to make some sort of shim in order to get the motor to sit flat on the back. However, I was thinking about killing two birds with one stone: reinforcing the transom with a 1/4-inch to 3/8-inch [thick] aluminum plate and using the plate as a base for the shims. I have access to a machine shop so I can make whatever I need. I was thinking an 18-inch-wide or so plate that extends a few inches below the bottom of the motor mount.

Does anyone have any experience with this? Any comments? Any ideas?


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Re: 13-footer Transom Reinforcement

Postby jimh » Tue Jun 05, 2018 2:35 pm

Have your read the owner's manual for the 13-footer? Compare at

http://continuouswave.com/whaler/refere ... stallation

Here is an excerpt "ENGINE INSTALLATION":

9, 11, 13, 15, and 17-foot

....On 9, 11, and 13-foot models used as tenders where low horsepower engine may be removed frequently, some elect to install an aluminum plate on the transom interior....

11, 13, 15, and 17-foot models, with higher horsepower engines, require engines to be bolted onto the transom in addition to clamping. This is no problem as in most cases the engine splash well is sufficiently deep....

On 13-foot models (prior to 1986) the transom is slightly curved. If on larger, newer engines there is a space between the engine and the transom, washers can be used to fill the space to prevent bending or placing too much pressure on the engine bracket when the bolts are tightened up. 13-foot models after 1986 have a flat raised area on the transom for engine mounting.

On a 1968 boat, adding some reinforcement to the transom at the engine mounting point is a good idea. The boat is 50-years-old, and the transom might not be as strong as it was at the time it was manufactured.

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Re: 13-footer Transom Reinforcement

Postby TommyWhaler » Thu Jun 14, 2018 4:48 pm

The first thing I think of when I see a metal plate on a transom is: PROBLEM

Think about that when you go to sell.

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Re: 13-footer Transom Reinforcement

Postby dg22 » Thu Jun 14, 2018 8:09 pm

It may not be a bad idea but I've had no problems with my transom. I have a 1967 13-footer with a 1973 50 HP Evinrude, short shaft. I have it on the transom with no shims or no reinforcement plate. I did add a thin piece of sheet metal that my Dad had sitting around. We folded it over to protect the fiberglass and then we clamped the motor on and used the top two bolts. I've never had a problem and I've had it on there for at least 8 years. If I was to add some additional support, I may put a thin piece of aluminum on the inside of the transom that I could bend in place. I'm adding a tilt and trim unit this year.