CONTINUOUSWAVE

I just made a trolling motor mount for my 1986 Montauk 17, and I installed the mount on the weekend of June 6-7, 2026.

I used 3/8-inch [thick] aluminum [plate] and mounted the Minn Kota RTA-17 motor to it. I then placed that whole assembly on at the flat bow port-side section or bow step.

Next I calculated the proper spacing so the trolling motor could be deployed and not hit the rub railing, as well as making sure it was centered on the bow step so the screws would hit the wood underneath.

To allow the plate to sit flat onto the bow step I had to trim away some of the rub rail. There is wood in this area. I screwed the plate down with ten #14 1-1/2-inch-long 316 stainless steel screws, and I used 3M 5200 adhesive to secure it [to the deck of the hull]. I used 3M4200 in the section under the plate to fill the gap by the rub rail. I used a little more 3M5200 and 3M4200 than I needed, but better safe than sorry.

The sealants oozed out of the screw holes and I just wiped away what I could . Then decided I might as well seal the tops of the screw heads so water doesn't seep into the bow step.

This mount was much cheaper than some of the aluminum slider plates I have seen online, and it is simple. I think it turned out well and will be plenty strong--this thing isn't going anywhere.

I still need to clean up some of adhesive and sand down the screw heads that I covered with extra 5200 that leaked out.

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ASIDE--Breaking Screw Fasteners When Threaded into Fiberglass
Screwing any self-tapping fastner into this boat with the fiberglass is crazy. I never thought fiberglass like this could break off a screw head if your pilot hole wasn't the right size, which happened with some smaller screws in my console (not with theose massive #14 screws). As I put each screw in with my Rigid Impact driver, it felt like I was going into concrete.

farnsrocket wrote:I used a little more 3M5200 and 3M4200 than I needed, but better safe than sorry.

As seen in Figure 1 below, I think you went overboard with the 3M adhesives. If they cured into a strong bond with the gel coat, you will most likely never be able to remove the trolling motor mount from the bow non-skid deck area. The bond of the gel coat to the mount is probably stronger than the bond of the gel coat to the foam. And if the bond of the gel coat to the foam is still very strong, then the shear strength of the foam is probably less than the shear strength of all the adhesives to the metal.



I have some experience in trying to remove something from a fiberglass hull that was bonded with a marine adhesive.

Cf.: Refitting a through-hull depth sounder transducer
https://continuouswave.com/maintenance-logs/newDS/

A recent project involved removing an antenna ratchet mount. I suspect it was bedded onto the cabin side with a very strong adhesive. The mounting plate, with the four 1/4-inch through-bolts removed, was so firmly glued in place that it still held up the radio antenna and four-foot extension mast, and the mount showed no sign of budging. I am going to try heat and a multi-saw to wear down the adhesive. The goal is to not harm the underlying gel coat.

I had a good result when removing a piece of Starboard from the transom of a Dauntless 16 which had been mounted with 3M5200. I used a length of multi strand fishing line. I tied the line to a handle at each end and used the line as a saw.

jimh wrote:If they cured into a strong bond with the gel coat, you will most likely never be able to remove the trolling motor mount from the bow non-skid deck area.

That was my goal ( :

[There is] no reason to ever take off the [the trolling motor] mounting plate off once it is on [the foredeck]

I also used 3M5200 adhesive sealant and lots of screws [to fasten] a trolling motor plate [to something not described].

[The trolling motor mount] a good job.

Cala wrote:[There is] no reason to ever take off the [the trolling motor] mounting plate off once it is on [the foredeck].

That you have that opinion is very fortunate for you, as due to the use of a super-strong adhesive the mounting base plate won’t be removed without some special effort and perhaps not without harm to the deck gelcoat and laminate.

Eventually your trolling motor will require replacement due to wear or damage. You may find that after several years a "piece-part" or identical replacement is no longer sold. You would then find yourself buying a trolling motor that fits regardless of its features rather than a replacement that has the bells and whistles you prefer.