Carver Owners Forum

I’m about to install a new Depth-Sounder/Fish-Finder in my 26 Santa Cruz. Currently there is an old Apelco Fish-Finder with a transom mounted transducer and an older Lowrance depth sounder with two units, bridge and lower helm.

I’d like to install my new transducer inside the hull, but am rather unsure where to locate it. I’m hoping someone with the same boat, or one with a similar hull shape has some advice.

My options are:

1/ Under forward floor panel, which is roughly 1/3 of the boat length back from the bow. The Lowrance transducer was mounted there, but does lose lock from time to time when cruising around 12 mph. So maybe there’s some bubbles from the chines as the bow rises.

2/ Under the rear floor panel which is where I’d like to try it.

3/ In the engine compartment, which will be awkward to install.

4/ Transom mount, which will require a cable extender and barnacles/mussels do seem to like to call it home.

I’m looking for some general advice. I can move it around a bit on/in a plastic bag full of water to see how it works to pinpoint the final best place to epoxy it down.

Any thoughts?



Ps: Some tidbits of other information

1/ The old Apelco unit failed due to display issues. One of the ribbon cables feeding the LCD has deteriorated over time and can’t be repaired. The nice feature was it displayed speed as the transducer had a paddlewheel, although it did foul from marine growth mid-season.

2/ My new Lowrance unit will display speed, but only from a NMEA device, in other words GPS. But’s that’s fine as I am finally installing a Chart Recorder which can do that, however as both will be located very close together, I can always read speed on the Chart Recorder without making the NMEA connection.

3/ The cable for my new Lowrance Depth-Sounder is a few feet too short to reach from the bridge to the transom and an extender cable is require. It adds considerably to the cost, is way longer than I need, and the mid-cable connection point has some risk of failure, (although not much).

4/ I did call Lowrance on using the transducer to shoot though the hull and they said the only problem was some signal attenuation, so that it might not work at it’s maximum specified depth (approx. 900 to 1000 ft), but that should be fine as I’m generally in water under 100 feet and certainly not over 150 feet.

I definitely would try to put it in the back 1/2 of the boat, unless you can stay very near the centerline without getting it on too much of an angle. I take it the transducer is not one that has an integral angle in it? The rear compartment may prove the best if it has the least deadrise and no obstructions to disturb the flow.

I put a "through-the-hull" one on my boat last year. I also have a thru-hull on the other side for an older sounder/fishfinder.

Make sure that where you put it is not behind or in line with any thru-hulls or other appendages on the bottom of the hull, like the water intakes for the engines or generator, struts or shafts (do you have outdrives or straight shafts?). You want a clean flow of water under the sounder.

I don't know on that particular model, but you don't have any core in the hull below the waterline, do you? If you do, then it wouldn't be good for a through-the-hull shot, but I don't think those have cores.

Thank-you for your response. The old unit glued somewhat forward was to the side of a flat spot above the keel. I presume there may be a wooden filler piece under the flat spot. So that transducer was mounted at an angle, and a sharper angle than further aft.

I may try the engine compartment. I only have the space between the engine and the battery try to work with (although I could unscrew the battery tray and remove it, but then couldn't check to see if the transducer ever comes loose).

Slightly to the port side of that space I have the water pick-up for the engine (Mercruiser 260 sterndrive), so I could mount it on the starboard side a few inches ahead of the water pickup, but not yet under the battery tray.

The deadrise is less back there as well, although I thought of trying to glue the transducer at an angle counteracting the deadrise and making it level... if it matters much.

Your idea to try spots with it hooked up and in a ziploc full of water is good........I have done that and it works just fine....a little angle is nothing IMO.......if you epoxy that down properly there will be no worry of it coming loose unless you have night elves with chisels....

Whether mounting the ducer on an angle will be an issue for you depends on your type of boating. An angle will always give you an inaccurate depth reading as it forces the signal to take a longer path (diagonal) to reach bottom than it would if it were shooting straight down. The error gets exponentially worse the deeper you are. So while it may be a foot or two off in say 5-10 feet of water, it might be a 100 feet off in say 50 feet of water. Would have to brush up on my geometry and Pythagorean theory to do the math. In some cases it's not a big deal but if the angle is bad enough and you do the type of boating like I do by anchoring in very shallow anchorages, you don't want the reading to be off by much. In shallow water, an error could be the difference between floating and running aground. Most sounders will have an offset that you could use to compensate for the error in shallow water but the offset will only be accurate for a given depth/reference as the error increases the deeper you go because of the angle. The offset won't make that much of a difference with that kind of error.

Do you have the ducer already? For what it's worth, in a sterndrive application, a transom mounted unit has it's advantage over a shoot-thru-hull unit in that you'll likely get better definition, it'll be an easier install, you won't have to worry about it coming unglued, and you won't have to worry about the angle of the hull as you can get a straight vertical shot. You can get one with speed and temp and I don't see keeping it clean as being an issue, give it a wipe when you go swimming.

Viper wrote:Source of the postDo you have the ducer already?

I do have the transducer; a transom mount that came with the unit. My original intent was to mount it on the transom, but there's additional cable I have to buy to extend its reach.... most of it to be coiled up, as the original cable is only short a few feet. After speaking to the factory Service fellow, he claims it will still work fine as I don't travel over deep waters.

As to glue it down level, I was thinking of making a little damn around it... out of plasticine, or clay, or even RTV, to hold the epoxy from running out while its curing. Leveling the transduce would therefore not be a problem.

I was checking under the boat today and found a curious thing. There are a total of 4 strakes along the hull, two outer, and two inner per side. The outer ones end at the transom, but the inner ones stop some 5 or 6 feet from the transom AND curl inwards for about 2 to 3 inches towards the center line. I'm not sure why, unless it is to direct some water flow under the stern to provide a little more lift.

At any rate, it seems mounting in the engine bay may not be good due to turbulence from these 90 degree inwards pointing strakes. I'll have to do some precise measuring to tell for sure.