Mounting transducer to transom board

[dvan1901]

I'm getting ready to mount a transducer to my transom and had a couple questions. First, I'm planning on using a mounting plate; can I just 5200 this to the transom without screwing it in? Second, I have a catameran style hull with a Bravo III drive and I was thinking of mounting the transducer just to the right of the middle drain plug (see first picture):

From this picture, you might think the spot to the right, where the hull goes up and levels off, would be best, but if you look in the second picture, it is a slightly curved surface and a steeper angle:

This part of the hull is always in the water, but i'm wondering if the counter rotating props will cause problems in this location.

 

[jtexas]

Re: Mounting transducer to transom board

If your talking about right up against the outdrive, I would predict too much turbulence there. what kind of plate? can it be contoured to the hull? wonder if marine-tex would work here?

5200 is really powerful stuff once it cures, BUT, the force of the water on the 'ducer is pretty dang powerful, too.

I guess you considered shoot-thru-hull and decided against it?

 

[dvan1901]

Re: Mounting transducer to transom board

I did consider a shoot through, but I can't readily get to a place in the hull that doesn't have a glassed in board for re enforcement. The hull is pure fiberglass, no core, but much of it is re enforced with plywood to mount things on, like the bilge pumps.

I do believe the mounting board can be cut to contour the hull. Think Rig Rite boards. The mounting location will actually be about 3-4" to the right of the drive. I was thinking this location would have the "cleanest" water passage because it occurs before the drive.

After further reading, it seems that the drive turbulance issue is more to do with inboards so that may not be an issue at all.

 

[ziemann]

Re: Mounting transducer to transom board

I think that area to the right of the plug will still be way too turbulent. I would say you need to be a good 12-16 inches from the prop to find clean water....

You might be able to get away with a 5200 application. Just keep your transducer close to flush with the bottom of the hull to keep the drag on the transducer to a minimum. What I would fear is that you would hit something like a stick at speed with the transducer and before it can kick the transducer up, the impact also tears off the mounting board.... Maybe that isn't realistic...but it is the thought that goes through my mind....

 

[jtexas]

Re: Mounting transducer to transom board

You might think that the outdrive just parts the water as it gets to it, and you might be right. Only a hydrodynamical engineer would know for sure, which I am not one of, but I have this idea that maybe (probably) the water can't get out of the way that fast - it pushes a wave in front of it, like the bow wave out front of a displacement hull.............

 

[fishmen111]

Re: Mounting transducer to transom board

What they said. Dvan, I would not mount it that close to to your outdrive. You really need to have it at least 12" from there. I also would not 5200 a board to the hull. I would put 5200 on the ss screws you use to mount it. When something strikes your transducer (believe me...it will), it is designed to flip up but you need enough resistance on it to keep it from coming up from just water pressure. I fear that an impact would be enough to separate the glued board without screws. I know you don't want to drill that nice boat, but if sealed properly, there will be no issues.

 

[dvan1901]

Re: Mounting transducer to transom board

I think I have come to grips that using the screws is the right thing to do, and if sealed correctly (is a whole tube of 5200 excessive!) it will be fine. So, now where to mount it. If you look in this picture, you can kind of see the area to the right a little better. It's kind of rounded and if I keep going right, I hit the trailer...

 

[jtexas]

Re: Mounting transducer to transom board

my vote:

that really is a great-looking boat, by the way.



masking tape where you predrill for the screws, makes cleaner edges on your holes.

 

[dvan1901]

Re: Mounting transducer to transom board

Thanks jtexas, we have been thrilled with the boat. I will try and take a picture later this week of that area you circled and get a better view of what I have to work with there.

 

[dvan1901]

Re: Mounting transducer to transom board

Update: The transducer showed up today (Airmar P58) and something I wasn't prepared for was how large of a hole I have to drill to get the connector through; it's a good 1/2-3/4" wide. So, to accomodate this, I'm thinking of putting the hole above the rub rail, under the swim platform (see picture):

This area does get wet when the boat stops, but I was still going to seal the crap out of it with 5200, and it has a cable cover that I can put on and 5200 the opening to that too. I was thinking of this location because there isn't wood there to run the risk of rotting and my hull is pure fiberglass, no wood core. Thoughts?

 

[jtexas]

Re: Mounting transducer to transom board

That's what I'd do, run the cable through above the waterline, pretty it up with a grommet.

Some people find that 5200 is too permanent for some applications, and prefer 3m 4200 for stuff that might need changing in the future. Personally I haven't encountered that problem.

Just something to consider.

 

[dvan1901]

Re: Mounting transducer to transom board

Thanks jtexas, I did think of that, but figured if something ever changed, like a new transducer, i would just cut it and drill it back out with the same size bit. Kind of what people do with epoxy and engine mounts and such; drill a larger hole than required, fill with epoxy, then drill smaller, required, size hole.