Materials and Methods to Use to Mount a Transom Transducer

Electrical and electronic topics for small boats
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Materials and Methods to Use to Mount a Transom Transducer

Postby OldKenT » Wed Jul 10, 2019 5:42 pm

I have selected a good location for installing my Totalscan transducer to the transom of my 1985 17-foot Newport, so the next step is to install it, and I would appreciate advice and comments on the following options:

  1. Attach a block of KING StarBoard to the transom with stainless steel screws and then attach the transducer to that.
  2. Use 3M 5200 Adhesive and Sealant to attach a block of cellular PVC to the transom without using screws and then attach the transducer to that.
  3. Attach the transducer directly to the transom.

Option 1 was my original intention only because KING StarBoard is HDPE material, and I am assuming that it will hold the transducer screws quite well. Also, if necessary, the block of KING StarBoard could easily be removed in the future and the holes properly filled.

Option 2 was recommended by an installer at the marine shop which installed my new outboard last year. I have confidence in the shop, although he was not the installer of my outboard and I do not know his background. He said that cellular PVC (which I already have) would be appropriate and much less expensive than KING StarBoard and would work just as well, and that the 3M5200 Adhesive and Sealant would form a strong bond between [cellular PVC] and the gelcoat on the transom. He stated that he does this on all the inflatables they sell, and recommended spreading the 3M5200 Adhesive and Sealant over the entire back of the block of cellular PVC.

Option 3 is the only other alternative I can think of, and I expect that either option 1 or option 2 is preferred, but I want to leave it open for comments and advice.

I have read the materials posted previously on this site, and appreciate the advice given previously. Up to this point, I am unable to find any downside to using the 3M 5200 Adhesive and Sealant.

So, here are my questions:

Q1: Which option would you choose?

Q2: Is there any downside to using the 3M5200 Adhesive and Sealant, other than that removal of the block would be difficult, if at all possible?

Q3: If I use the 3M5200 Adhesive, would it be sufficient to just use it at the edges, or do I really need to spread it all over the back of the block?

Q4: And last, is the use of cellular PVC (such as is used in Koma, Azek and other such "plastic" boards) an appropriate alternative to KING StarBoard?


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Re: Materials and Methods to Use to Mount a Transom Transducer

Postby jimh » Wed Jul 10, 2019 5:53 pm

Of the three choices, I would select Option-1 or Option-3.

On my boats I have directly mounted the transducer to the transom, but on my current boat, the transom has collected quite a few unused holes from prior transducer mountings, some by the previous owner and one set by me. The transom is getting a bit of Swiss-cheese appearance. On the other hand, all the holes are very well sealed and they are all under water and mostly unseen. The only time the extra holes are objectionable is when the boat is on the trailer and being inspected by other Boston Whaler enthusiasts.

But on a 17-foot boat I would not expect that more than one transducer will be installed, and for that reason I would just use the direct to transom mounting.

KING Starboard is a boutique material. I think you can obtain similar material at a kitchen supply store in the form of a thick cutting board, or perhaps at just an industrial plastic supplier. KING StarBoard has a bit of pedigree and a higher price.

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Phil T
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Re: Materials and Methods to Use to Mount a Transom Transducer

Postby Phil T » Wed Jul 10, 2019 5:59 pm

OK -

4200/5200 does not adhere well to KingStarboard.

Go with Sternsaver since he has already got the blocks, special adhesive etc. and don't drill any holes.

The product inventor. Scott Johnson, aka Basshole, gathered input from us, offered a giveaway years ago when he was in the final design phase. Here is one of the threads. Note how critical some members were.
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1992 Outrage 17, 1992 Evinrude 115

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Re: Materials and Methods to Use to Mount a Transom Transducer

Postby OldKenT » Thu Jul 11, 2019 2:38 pm

Thank you, jimh and Phil T, for the replies and advice and for the reference to the prior string on the Old Forum about the SternSaver. I found it interesting that you differed in approach and I can see the desirability of both approaches.

I agree with Jim that using screws is the simpler and more traditional approach and will probably work just fine on this 17-foot hull, but I also agree with Phil T that the avoidance of holes in the transom by using StarBoard with an adhesive might be better and allows easier adjustment to the position of the transducer.

This morning I bought the SternSaver kit at West Marine. I was influenced by the fact that, although it is 34-years-old, this hull has never had holes in the transom except to mount the original 1985 Mercury outboard and the current Yamaha outboard, and I would like to keep it that way.

The one concern I can see with use of the SternSaver kit is that the location where I intend to glue the StarBoard block slightly overlaps where the transom changes planes, so one of the six glue holes on the block might not be usable. Whether that will matter is not yet clear, but I will need to read the instructions on that first.

Thank you both for your replies.