Transom mounting plates

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
f1loco
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Joined: Wed Jun 21, 2017 7:26 am

Transom mounting plates

Postby f1loco » Mon Oct 16, 2017 6:56 pm

I've a 9.8 Tohatsu that weighs in at a whopping 85-lbs. The transom on the 13-foot classic is fine. That said, I'd prefer to have one barrier of insulation between the two screws on the motor and the transom. But, as you know, our transoms are not flat; hence something flexible needed.

What do most of you all run?

I prefer something that I don't have to drill into transom; that's why I am trying to just bolt-up the motor.

I hear KING StarBoard is bad as it is too slick for the flats to bite.

I am not opposed to wood, but again rot is a concern.

I thought about T6 aluminum but unsure of how thick I can go and it still be pliable and bendable to flex it to shape.

jimh
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Re: Transom mounting plates

Postby jimh » Wed Oct 18, 2017 4:22 pm

The notation "T6" on aluminum refers to the heat treating or finish, not to the alloy. The alloy and the tensile strength best describes the resistance to bending. If you use a softer grade of aluminum, like 3003, you should have better results in bending it compared to using an aircraft grade like 6061T6.

A few years ago I made an instrument panel from 3003 aluminum plate that was only 0.080-inch thick. I was a bit worried while fabricating the panel that I might bend it. In contrast, the original panel was 0.1-inch 6061T6 and was significantly stiffer and resistant to bending. On that basis, I think you could perhaps persuade 3003 aluminum alloy of less than 0.08-inch to adopt a suitable shape to fit the curved transom.

THe problem in bending any material is how you will create a form. If you try to use the actual transom as a form you may find that the material you are trying to bend may be stronger than the transom.

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Dutchman
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Re: Transom mounting plates

Postby Dutchman » Thu Oct 19, 2017 10:11 am

A 2-mm-thick 3003 aluminum sheet will bend easily, as will 2-mm-thick T6 over the width you are looking at on the transom.
The question is inside or outside, as outside will be easier because you must truly form the inside curve.
Why not some nice wood?
EJO
"Clumsy Cleat"look up what it means
50th edition 2008 Montauk 150, w/60HP Mercury Bigfoot

jimh
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Re: Transom mounting plates

Postby jimh » Thu Oct 19, 2017 3:05 pm

There is no "T6" aluminum. "T6" is a heat treatment, not an alloy.

f1loco
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Re: Transom mounting plates

Postby f1loco » Thu Oct 19, 2017 4:05 pm

Thanks all. Managed to find Kent Fabrications. They make a beautiful piece to step up the transom top for a long shaft, but on request they can do the inside 0.25-inch-thick aluminum plate with mill finish made to fit just the inside of the transom without the step up. I hope to avoid screw holes, and will use 3M4200 to adhere the plate to the transom with a bead on the edges for a nice finish. I calculate that between the 3M4200 adhesive and the engine mounting clamps, [the outboard engine attachment to the transom] will be good for years and be attractive.
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pcrussell50
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Re: Transom mounting plates

Postby pcrussell50 » Thu Oct 26, 2017 1:33 am

Have you managed to get an actual response from KENTFAB?

I was almost ready to buy a [1972] 13-footer, pending hearing back from KENTFAB [about buying their transom lift product]. [I sent] multiple emails including, "I'm ready to buy. How do I pay you?" And, "If you're backlogged, I'll pay you in advance, just tell me how and how much. I can wait." I never got a single response. Not one. So I passed on the boat, too. I ended up with a nice 1985 Sport 13, with a gem featherweight Yamaha oil-mixing 40-HP, and never looked back.

I chalked up KENTFAB to another in the long long line of talented tradesmen who are horrible with people and business. This was Spring 2009 timeframe.

--Peter

f1loco
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Re: Transom mounting plates

Postby f1loco » Thu Oct 26, 2017 7:14 am

Yep, [the KENTFAB transom mounting plate is] supposedly in-route to me as I type.

Gmeehvol
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Re: Transom mounting plates

Postby Gmeehvol » Thu Oct 26, 2017 9:33 pm

[How much was the plate?]

f1loco
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Re: Transom mounting plates

Postby f1loco » Fri Oct 27, 2017 7:52 am

The plate was $140 total, but worth it; and I should never have to worry about it again: no rot, no cracking. Nicely rolled for 0.25-inch thick piece of milled aluminum.

[Kent Fabrications] were great. One week from contact to receipt of the transom mount. Now to the hardware store for four SS screws with the right beveled head. The plate should look pretty sweet once installed. Not to mention I can finally crank down the clamps on the outboard without fear of marring the fresh transom work.
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f1loco
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Re: Transom mounting plates

Postby f1loco » Mon Nov 06, 2017 4:55 pm

Plate all installed ... very sweet work. Re-pitched my 9.8 Tohatsu to the 5 pitch they have and finally screams at 5850 RPMs at WOT. Next up: bolting up through the transom ...
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StephenSegari
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Re: Transom mounting plates

Postby StephenSegari » Thu Nov 30, 2017 10:39 am

Any updates on this install? Do you have any additional photos? Thanks!
1975 13' Boston Whaler
Madisonville, LA

f1loco
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Joined: Wed Jun 21, 2017 7:26 am

Re: Transom mounting plates

Postby f1loco » Thu Nov 30, 2017 11:23 am

Just the one I posted above - but everything went in great. Having some work done on the boat and motor, including doing a through hull installation on the motor currently. I can post a couple of pics when I get it back.

StephenSegari
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Joined: Wed Nov 29, 2017 11:32 am

Re: Transom mounting plates

Postby StephenSegari » Thu Nov 30, 2017 11:32 am

f1loco wrote:Just the one I posted above - but everything went in great. Having some work done on the boat and motor, including doing a through hull installation on the motor currently. I can post a couple of pics when I get it back.

All good. I guess I'm confused on the mounting plate vs. the engine bracket. In that last photo, is the engine bracket installed, or just the plate? Going to google the plate now, would definitely like something to strengthen the transom further (or at least give me a little piece of mind).
1975 13' Boston Whaler
Madisonville, LA

f1loco
Posts: 17
Joined: Wed Jun 21, 2017 7:26 am

Re: Transom mounting plates

Postby f1loco » Thu Nov 30, 2017 11:58 am

Yes, just a plate was installed to give the inside some strength. Having the motor mounts drilled and mounted through transom as I type. Bracket are usually used create a set-off off the transom and/or lift it for proper trim or long shaft. The same fellow use to do a bracket that would lift the top of the transom even to allow a long shaft installed - I think that is where you are getting "Bracket" at - see my pic a few posts above.

StephenSegari
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Joined: Wed Nov 29, 2017 11:32 am

Re: Transom mounting plates

Postby StephenSegari » Thu Nov 30, 2017 2:54 pm

f1loco wrote:Yes, just a plate was installed to give the inside some strength. Having the motor mounts drilled and mounted through transom as I type. Bracket are usually used create a set-off off the transom and/or lift it for proper trim or long shaft. The same fellow use to do a bracket that would lift the top of the transom even to allow a long shaft installed - I think that is where you are getting "Bracket" at - see my pic a few posts above.

I see. You were just referencing the step up bracket also made by Kent. I'm going to give them a call and see if I can order the same plate. What length SS screws did you wind up going with?
1975 13' Boston Whaler
Madisonville, LA

Joe 15 SS LTD
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Location: Seffner FL

Re: Transom mounting plates

Postby Joe 15 SS LTD » Thu Nov 30, 2017 4:04 pm

What about dissimilar metal corrosion between the aluminum and stainless. I have had this on my Whaler after the dealer installed a pony motor bracket on my 15' Super Sport Limited. A few years down the road probably 15 years I removed the bracket and found some minor corrosion. I ended up using some sheet pvc for a washer to separate the bracket from the bolts. I also had the pony motor bracket powder coated.
The pony motor bracket is aluminum and bolts are stainless

f1loco
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Joined: Wed Jun 21, 2017 7:26 am

Re: Transom mounting plates

Postby f1loco » Thu Nov 30, 2017 4:51 pm

Yes, overtime aluminum and SS is a bad combination, let alone with salt water mix, but alas, it's only going into wood and the reaction to the point of contact should be minimal if kept clean. Besides, I put 5200 on mine - that's what I am more worried about. But then again, as you indicated, I don't plan on having to do anything with it in the next 15 years.