JackC

I will be picking up my new Maritime 20D in a week or so. I have mounted many transducers but hate drilling into my new transom. Is anyone mounting a small piece of "starboard" on their transom to avoid this issue - if yes, what is the technique?

Any comments on drilling into the Maritime's transom (if I go this route) are also appreciated. Its a "no wood" transom so drilling into it may not be an issue.

I got lazy and Atlantic Outboard is painting the bottom for me - so the hull will have bottom paint on it when I get it home.

Thanks - Jack

Bryan A.

Just drill the holes oversize and backfill them with epoxy. Re-drill and mount, that should seal the core.

My Parker came with a piece of starboard holding the transducer and I'm not to keen on it. The only reason I'm not changing it is because it is already there and it is hidden away under the bracket but I see no benefit unless you change transducers a lot.

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2003 Parker 2530 "El Mar".......click the pic
1973 Seacraft 20SF

AlloyToy

JackC,

Use a c'sink and c'sink the drilled hole out to the major diameter of the screw. This stops any gel coat chipping or cracking.

When I had my MS I mounted the transducer direct to the hull. I have seen the starboard trick but I really don't understand the advantages. You have to drill holes to mount the starboard anyways.........

Gotta be getting excited now!!!!!

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"First The Bite Then The Fight"

JackC

Thanks for the chat. Yes, I'm getting excited but the weather needs to get better for me to get really excited. I THOUGHT the starboard was put on with epoxy. I'll go the traditional route right to the transom.

I assume there are no tricks to drilling into the transom with the "micro spheres" (or whatever they call them).

Jack

Scup

Been following this post as several of my customers (West Marine Associate) ask me this same question each year. While West Marine does train us, and requires that at least once a year we maintain our status, this post goes into far more detail than I was ever taught. I know, that even with a core construction, there is no way you would want any chance of seepage into the transom under any circumstances. Just to be sure I got it right I condensed everything heard and added a few things so correct me if I am off base anywhere or I will be spreading some hate and malcontent among my customers.

1. Read the instructions provided by fish finder manufacturer concerning transducer placement carefully. (I would think this is one thing you would really want to get right the first time)
2. Drill a small pilot hole to guide a countersink to the depth such that the width of the counter sunk hole matches mounting screw's major diameter to prevent gel coat cracking.
3. Counter bore pilot hole with an oversize bit.
4. Fill counter bored hole with structural epoxy putty such as Marine Tex.
5. When cured, drill proper sized mounting holes
6. Coat threads of screws with lubricant such as silicon
7. Mount transducer
8. Paint transducer with anti fouling water based paint or transducer paint

Something is wrong here! What has me troubled is if one countersinks to screw's major diameter, then re-bores it with an over-sized bit, which has to be larger in diameter than the screw's major diameter, what is the purpose of counter sinking in the first place as you would be drilling right over it anyway? Is it possible the term screw's major diameter means diameter of the screw's head, then it makes sense although I am not sure if I got it right just yet? Let me ramble on for a little bit more as you guys got me thinking about this. I like the idea of drilling an over sized hole and filling it with structural epoxy. If one would just drill straight into the transom and mount the xducer, we know that no matter what gunk you put on it there is always the danger of seepage. However, there appears to be something than can still go wrong with Brian's method if not done right. Suppose the length of the mounting screw is one inch. The depth of the over sized hole then should be something greater one inch or else the only thing to prevent seepage would be the 5200 or whatever gunk you stick in there. If Brian's method is done correctly by going deeper than the mounting screw, then even if the gunk fails completly (not likely) there is no way that I can see where seepage can ever occur.
I am also wondering what is wrong with JackC idea of epoxying the starboard directly to the transom. Epoxy takes to starboard, the stuff should last forever, the epoxied surface area would be so great that the strength of the bond would go out of sight, and there is not a lot of structural stress on a Xducer anyway. I can understand JackC's concern as I would not like to put holes into a new $1000 per foot hull. God forbid, but if JackC has to tweak his Xducers position because of some unforeseen cavitation problem, no problem with starboard. From what I read about JackC's ride, it could be around longer than JackC. Sooner or later, the fishfinder is going to be outdated and have to be replaced. Again, no problem with starboard or a xducer change out. I am trying to put myself in JackC's shoes, listen to everyone, but the final decision is yours. What ever you decide JackC, do not listen to me as I have only mounted one xducer in my life and it was a piss poor job. Likely all the suggestions will work out fine, but I am curious what the pros on this form will eventually come up with as the best way of going!

Bryan A.

The epoxy will not stick to starboard. It is almost impossible to get anything to stick to that stuff including 5200. Try it if you don't believe me.

What you want to do is drill out the holes big enough so there is no possible water intrusion when the screw hole is drilled into the epoxy. I would start with a 3/8' bit or so, countersink as Alloy suggested and then fill with a epoxy, cabosil mixture. Make sure to fill the entire hole to avoid an air bubble. The pic below is from the West System website. Do it similar but make sure the epoxy goes to the bottom of the fastener.



Advanced fastener bonding

For greater strength and stability, drill oversized holes to increase the exposed substrate area and the amount of epoxy around the fastener. If the fastener/hardware can be clamped by other means, the oversized hole can be extended to the end of the fastener.

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2003 Parker 2530 "El Mar".......click the pic
1973 Seacraft 20SF

Bob & Mag

Jack, I mounted my tri-ducer directly to the transom on our maritime. no problem. Take you time, measure carefully. I drilled the holes and use a c-sink as mentioned to prevent gel-coat cracks. I put some 5200 on the screws(4200 also could be used) and mounted the bracket.There is some play in the bracket for adjustments but it's best to spend an extra few minutes when aligning it before drilling.
The starboard method is simply this:
Cut a piece of starboard to fit the transon area and large enough for the tri-ducer bracket. Mount the starboard to the transom using 4200, so you can remove it later if need be. The trick to get the starboard to stick to the transom, as nothing will stick to the starboard, is use a dovetail bit in a router. Rout a couple grooves in the starboard face that will go up against the hull, doesn't need to be very deep. The 4200 should fill these grooves and also on the face of the gelcoat. This helps prevent the starboard from tearing off. Check with Paul D. on this method as he's a big proponent of it.
I'm afraid that if it pulls off at speed things will be flying hard and fast.

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Smoke free 6+ Months!

Bob & Mag

Jack, Did they tell you they had the measurements and didn't need to float the boat to establish a water-line????
They did me and boy were they off. Had to bring it back for them to repaint mine. Was easy as I just tied it up in their slip. I didn't need to pull the boat, they took care of it all.
Just curious if they adjusted those numbers.

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Smoke free 6+ Months!

Bryan A.

Neat idea!!! Learn something new every day.
I found a thread on stripers online talking about the same techniques to fasten fly rod holders.

Boat Rod holder - SurfTalk

for a transducer, I would be afraid of that thing flying off at speed though.
One guy packed the dovetail groves with Marine Tex, then used the 5200 to stick it to the inside of the hull.

Anyone got pics or want to go into further detail about this technique???

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2003 Parker 2530 "El Mar".......click the pic
1973 Seacraft 20SF

Scup

Several of my customers purchased starboard to be used to make storage boxes, tables, seat foundations and other specialized stuff. No one ever got back to me on how their projects worked out. I just assumed things worked out well for them but for all I know they just might have been using mechanical fasteners to build their stuff. After running my hand along the surface of a piece of starboard, I believe you Brian when you say things will not stick to it. That stuff is as smooth as a babies ass. It also seems to have a Teflon like composition. Was wondering if one would be better off using a shallow dovetail bit such that the base of the rout channel is wider than at the surface? I am starting to think that it would be far better for me just to write down the address of this website on a piece paper and hand it over to anyone asking about mounting a transom xducer. I noticed that JackC is currently off line. Is he going to be surprised when he comes back on and sees what he started, and it's probably not over yet!