North Australian FISH FINDER TM forums

Any one got any thoughts on mounting a transducer for through hull operation in a 4.5mt tinny? I tend to bash around a bit in skinny water dropping crab pots etc and have just busted my 3rd mount in as many years so I was looking at the option of mounting it internally. Just curious as to if/how you can shoot through aluminium and if there would be any affect in performance?



Melv

Yep there will be.

The aluminium will reduce both the outgoing signal and the return echos.

Have done it in circumstances where sensitivity wasn't an issue.

The answer is to simply use more power and rely on the increased signal in both directions to make up for the loss.

If u're only looking for depth its ok.

If u're using the sounder for fish finding or similar u'd be better off getting a box made up to insert into the hull and mount the transducer looking down. Fill the space between the transducer and the bottom of the box with silastic or similar with no bubbles. Make sure the silastic is smooth as it is levelled with the hull to eradicate any turbulence.

As long as the transducer is mounted sufficiently back far enough that its still in the water when planing.

Then the transducer is protected. The transducer is solidly mounted. Hull integrity is maintained. There are minimum losses in the system.

Will do up a diagram if u like.

Hi Seadog
Depending on what brand of sounder you are using you should be able to purchase a transducer that is mounted through the hull from under neath and sealed with Sikaflex or the like. I have these type of transducers fitted to all of our hire vessels and have done for about three or four years now and have now problems with them, you can purchase plastic or bronze ones(we use Humminbird brand units). If you Google Humminbird + through hull transducer you should find what I am talking about we use part number XFM 9 20
Http://store.humminbird.com/products/313999/XFM_9_20 this should be slink to the correct page on the web.
Cheers Greeney

check out attached - no holes in hull!

Clean the area with dliuted etching acid, big blob of silastic, jam the transducer into the sliastic, work all the air bubbles out and Bob's your uncle. That's what I did in my old 3.7 tinny, work a treat!

Thanks for the replies fellas looks like I've got a few options. Ronje - a diagram would be beaut if you've got the time. Greeny - that looks the goods but I always struggle with the idea of putting holes in the bottom of a boat. Very low profile and I guess if it stands up in the hire fleet should be no probs, might be the way I go. NT Fizzer - is that a thru hull unit mounted on a custom base inside the boat? Blinky - that's more my style

Thanks again guys


Melv

Firing thru an aluminium hull will reduce the effectiveness.

OK if u just want basics like depth/obstacles.

Put a transducer in the bow of the local marine rescue aluminium vessel. Angled it so that it was pointing just ahead of the bow. Traditional mounting worked ok but only gave info at back of boat AFTER u passed over it. One in bow showed what was there 3-4 metres BEFORE u reached it. Great for estuary with sandbars/rocks etc.

No good on plane as hull was out of water. Worked at slower speeds. Very, very useful. Had a back/front switch on transducer lead.

If u're only working a few metres of water u'll get away with Melv's idea. Not so in deeper water like offshore stuff/reefs etc.

The thru-hull fittings (even those nearly flush) are still vulnerable.

Will put up a diagram of a tried and true method a bit later tonight.

I've had 9 boats with through hull transducer, so far. The first boat has done excess of 3000hrs and still going with no dramas! The are all Humminbird transducers though.

Hi

Get an aluminium box made with no botton in it. Make iy just big enough to take the transducer head u have (or are likely to have if u get a new sounder at any time)

Basically you are putting a recess in the hull so that the sounder head is recessed and not sticking out at all. Its even below flush level.

Get a hole cut in the hull down towards the stern and weld the box into place with open end down and flush with hull opening making sure its watertight.

Install transducer with head about 25mm back from opening.

Fill with silastic or similar so its smooth across the opening (no turbulence) and no air bubbles in silastic.

Guaranteed that there'll be no damage to transducer no matter what you run up onto or hit.

That's your basic decision. Do you want to eradicate the risk or reduce it.

To eradicate the risk, fit the box.

To reduce the risk, put a thru hull fitting as Greeny suggests.

Other methods simply reduce the risk of damage. They don't eradicate the risk.

I made a wet box in a tinny when I snapped a transducer on a remote trip. I filled it with sunscreen and dunked the transducer in there. Worked well and saved the trip!

I have had through-hull transducers on three cartoppers, with el-cheapo low-powered sounders, and they worked fine, but definitely not as well as an external. As ronje says, they are OK for depth and locating rockbars and reefs.

Push the transducer down to create a very thin film of adhesive to minimise signal loss.

Road corrugations can pop off or damage internal transducers, so it pays to support them well.

I like the transducer mounts already pictured, very tasty. The box one if made too big would hold a tree stump nicely though, could be a devil to get the boat off ... everyone knows tree stumps are magnetic, even to aluminium and plastic

Hey greeny, is the angle of the beam adjustable on the transducers on your boats? they don't appear to be so theoretically given the "V" on most hulls wouldn't the beam be skewed out from whichever side of the keel its mounted? in 30+ meters of water a few degrees makes a big difference.

Hey Ken_dog
You are correct they are not adjustable. In the instructions that come with the transducers it states that you should make angled spacers to allow for the dead rise in the hulls, even when you fit these angled spacers I find that still only protrude a couple of mm from the hull.
I have noticed in the Garmin brand trough hull transducers you can order different units that have a certain degree of offset and you order the one that is closest to your hull shape, I think this is a excellent idea no spacers required.
Cheers Greeny