drilling holes in aluminum

[perceyg]

I am getting ready to drill four small holes in the lower rear of my aluminum boat to mount a block of wood so i can mount my transducer, if i get some rubber washers and silicone caulk the bolts will it be water tight? Any suggestions would be great. Thanks

 

[CheapboatKev]

Re: drilling holes in aluminum

I used 3M 5200 when mounting my transducer, no rubber washers.
Not a drop of water comes into my boat..

 

[Aussie Bunyip]

Re: drilling holes in aluminum

Screwing a block of wood onto the aluminium may not be a good idea. Aluminium is similar to stainless steel when it corodes. It is essential that oxygen is freely available to the surface of the aluminium so that a very thin layer of aluminium oxide can form. It is this oxide film that provides the aluminium with its anti-corrosion qualities. If the wood is seated on the panel, the oxygen can be replaced by water and moisture in the wood. This leads to horrific corrosion. Perhaps a better way would be to use a nylon or polypropylene board to mount the transducer on and seat this on a layer of "Sickaflex" which is what we use here in Australia when "bedding" anything onto aluminium or fiberglass.

 

[robert graham]

Re: drilling holes in aluminum

Maybe just keep it simple, drill 2 small holes, 2 stainless steel screws, small blob of silicone on the outside and the inside of transom, no problem! Good Luck!

 

[Bob's Garage]

Re: drilling holes in aluminum

Maybe just keep it simple, drill 2 small holes, 2 stainless steel screws, small blob of silicone on the outside and the inside of transom, no problem! Good Luck!

See the previous 2 posts. Stainless and aluminum do not like each other over the long haul. Check the corrosion on an aluminum trailer around it's stainless steel bolts.

Use the 5200 and wood, much better idea. The fewer holes the better when you are discussing a boat hull, of any construction.

 

[robert graham]

Re: drilling holes in aluminum

My aluminum jon boat has all stainless steel screws and bolts holding all accessories like transducers, fishfinder, bimini top, etc., with no apparent corrosion issues. Maybe the aluminum/stainless corrosion issue is with saltwater boats or boats left in the water? My transducer has been held on by 2 stainless screws since new in 1999 with no problems at all. Good Luck!

 

[ShadowB]

Re: drilling holes in aluminum

Same as CheapboatKev on mine boat. Used 3m 5200 to mount my Hummingbird transducer several years back, no rubber washers and not a drop of water leaks.

 

[Mel Taylor]

Re: drilling holes in aluminum

I mounted my Humminbird transducer on my 14 ft. MirroCraft in 1984 or '85 using stainless steel screws and silicone. It's still there with no signs of leakage or corrosion yet. However, my boat only stays in the water for a few days at a time. I don't know what would happen if it were there for an extended period - say an entire summer.

 

[BoatNoobie]

Re: drilling holes in aluminum

wouldnt the wood rot eventually? Or if you're using pressure treated wood, wouldnt that cause corrosion on the aluminum?

Iboat sells a block of plastic for this purpose. It's only like $12 and I bought 1 for my boat.

 

[JimS123]

Re: drilling holes in aluminum

Buy a piece of 1/4x2 aluminum flatstock at Home Depot. Cut a section about a foot long and mount (bolt) the transducer on one end. The bolt holes will need to be countersunk on the back for the flathead bolts, so the bar is smooth on the back.

Drill 3 mounting holes on the other end of the bar. Position the bar on the transom so the transducer is in the right place. the mounting holes should now be on the upper wood portion of the transom. Screw or bolt it in place and seal the holes with 5200.

Those mounting holes will not be below the waterline.

 

[Bob_VT]

Re: drilling holes in aluminum

Here is the bottom line use 3m 4000 or 5000 series sealants.

Do not use any PT wood.........

and I would avoid silicone since it is known to fail!

 

[mike343]

Re: drilling holes in aluminum

Glue it on with 5200. Or put the transducer on the inside of the hull.

 

[AGENT 37]

Re: drilling holes in aluminum

When installing any below water line accessories on my aluminum boats I have used 3M 5200 and stainless hardware. I coat the mating surface of the accessory as well as the hardware. It is the proper way to do it as any professional rigger will tell you. I use it for motor and trim tab mounting as well. It creates a barrier preventing water intrusion into the holes and also keeps water from getting trapped between what ever you are installing and the hull of the boat. To an extent it also helps reduce galvanic corrosion by applying a layer of isolating material between dis-similar metals. Do not use silicone, it breaks down with exposure to gas, oil, and sunlight. Use 3M 5200. Do not use wood, it will eventually rot.

 

[Capt'n Chris]

Re: drilling holes in aluminum

Put it on the inside?

 

[Jayrock]

Re: drilling holes in aluminum

Put it on the inside?

Shoot through hull. Very common. Most transducers can be set up this way. It helps at higher speed as there is no cavitation to wash out the echoes. You loose a little of the sensitivity, but it is an option.

 

[fishrdan]

Re: drilling holes in aluminum

Put it on the inside?

Shoot through hull. Very common.

That isn't going to work on an "aluminum" boat, unless he gets an Alumaducer.

I'd just drill your holes, apply a liberal amount of 3m 5200 or 4200 (Walmart has Attwood Marine Sealant) screw down the transducer and clean up what squishes out with paint thinner.

If this is thin aluminum you might want a backing board on the inside, a chunk of cutting board (WalMart) can be used. Drill your holes through the boat and piece of cutting board, apply 5200 to cutting board and fasteners, tighten it down and clean up the excess sealant.

BTW, I picked up a big cutting board from Sams Club ($10) so I'd have some plastic for the boat. It's not Starboard, but close enough for me.

 

[Bob_VT]

Re: drilling holes in aluminum

Well..... Just an observation......... must be Winter to drag up a 2 month old thread that the original poster has never re-posted in

 

[tomynoks]

Re: drilling holes in aluminum

He finished installing the transducer on Nov 29th and has been laughin ever since!!! I like threads like this though...good ideas come up... Mine is screwed directly to aluminum w/ 3m 5200 on screws and mating surfaces... works just fine.

 

[ShoestringID]

Re: drilling holes in aluminum

Personally I use a poly board on the transom for transducer mounting for a couple of reasons... I can mount one or many transducers and cable ties to the poly board without drilling a zillion holes in the transom, the poly lasts forever, and a couple of SS screws and some 5200 and the board will never ever come off. Cabelas sells the boards but I got a 3/4" poly "cutting board" at a local restaurant supply store for really cheap and it works great.

 

[fishrdan]

Re: drilling holes in aluminum

drag up a 2 month old thread that the original poster has never re-posted in

:facepalm:Arrrgh I hate it when I waste the time to read or reply to an old post,,,:facepalm: