Transducer in bilge???

Since I have a nice Garmin bottom machine (actually it is a GPS, but I have a bottom machine accessory that goes with it) which is sitting in my shed unused, I want to use it in the Gulfstar 36 that I just bought. The boat already has a working depth indicator onboard, and so I do not want to mount the second transducer by drilling a hole in the hull at this time. I could mount it on the transom of course, but don't really like that idea either. So was thinking of just making a box and putting the transducer in the bilge immersed in liquid until I have my next bottom job. Anyone have any experience with doing such a thing? If so, would appreciate comments.

I have a Humminbird digital display, the "Shoot through hull" puck type transducer is mounted inside the hull. I found a good spot by filling a ziplock bag with water and setting the transducer on top of it, trying a couple of different places. When I found one I liked I made a glob of wax from a wax toilet ring seal, I pressed the transducer down onto the wax on the hull and wiggled it around to squish out any bubbles and it has worked fine. It does not seem to intefere with the original Ratheon sounder.
Installed about 3 years ago no problem so far. It gets hot in the engine room and the wax gets soft but as long as it is not bumped it has stayed in place fine, of course it is on a relatively flat portion of the hull.
I understand they will not work through a cored hull.
Steve W

I have the Airmar P 79 transducer connected to my Garmin system and it works just fine. No need for extra holes in the hull.



http://www.amazon.com/Garmin-AIRMAR-Plastic-adjustable-hull/dp/B000EPLPWI

If you are considering mounting some other style of transducer, it can probably be made to work but you need to be sure it's pointing straight down, not at an angle and you need a way of keeping the fluid from leaking out or evaporating.

Some good responses, and very helpful! After giving the different options some thought, I decided to order the Garmin Airmar P-79 transducer, as that struck me as probably the easiest way to do it. Found it on amazon.com for $80 with free 2-day shipping.

The "shoot through the hull" article was great! Thanks!

rwidman said:

I have the Airmar P 79 transducer connected to my Garmin system and it works just fine. No need for extra holes in the hull.

Amazon.com: Garmin AIRMAR P79 Plastic, adjustable in-hull mount, Depth: GPS & Navigation

If you are considering mounting some other style of transducer, it can probably be made to work but you need to be sure it's pointing straight down, not at an angle and you need a way of keeping the fluid from leaking out or evaporating.

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I have the same transducder as you have it will only read to 800 ft or so what is the max yours will read? thinkin have maybe I do not have the best spot in the hull

800 feet? My quest was to find a sounder that would read accurately in 1 1/2 feet. I don't care how deep the water is...I care about how shallow it is.

jeffnick said:

800 feet? My quest was to find a sounder that would read accurately in 1 1/2 feet. I don't care how deep the water is...I care about how shallow it is.

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I understand that I do as well but when fishing for dinner it is helpful to know where the 1000' depth is The ray marine unit on my last boat could do both

Why not just use a transom mount?

Garmin in Australia advised me I could run 2 depth sounders, one for each helm, off one transducer to avoid the hull resembling swiss cheese, so relying on that advice I bought their products. You definitely can`t. I ended up writing, with near instant effect, to Garmin USA to get it sorted out in Australia where Garmin had even resorted to denying giving me the advice.
Eventually I fitted the transom mount transducer included with the unit, inside the bilge. I put a large volume of silicone in a piece of plastic drainpipe cut at the bottom to the angle of the bilge to get it horizontal at the top, put the transducer into the gloop, using a small level to get the foot level. It works ok but takes a while to get a "grip" on the bottom on start up. BruceK

GonzoF1 said:

Why not just use a transom mount?

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There is too much turbulence to mount it on the transom. Even with a thru-hull you have to avoid areas of turbulence,according to fitting instructions. BruceK

in my case I did want to pull the boat to install the transducer

My Humminbird Chart plotter came with a transom mount depth transducer. That piece fit nicely inside a 4" black ABS drain pipe. This pipe I cut to the angle of the bilge and epoxied it in place. a little light oil up to the level of the transducer and voila, good depth reading, to over 1000 ft.

I cut a piece of 4 inch pvc pipe and glued it to the hull inside the bilge. Filled it with silicone and immersed the transducer in it. Works fine and no need to drill a hole in the hull.

Some of the Gulfstars I have surveyed have balsa cored hulls but sections near the keel are solid glass. Make sure you locate your transducer in an area of solid glass or relieve the core at the hull interior to shoot through solid glass. I do not think your tansducer will ping through balsa...

jwnall said:

Since I have a nice Garmin bottom machine (actually it is a GPS, but I have a bottom machine accessory that goes with it) which is sitting in my shed unused, I want to use it in the Gulfstar 36 that I just bought. The boat already has a working depth indicator onboard, and so I do not want to mount the second transducer by drilling a hole in the hull at this time. I could mount it on the transom of course, but don't really like that idea either. So was thinking of just making a box and putting the transducer in the bilge immersed in liquid until I have my next bottom job. Anyone have any experience with doing such a thing? If so, would appreciate comments.

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Make sure you locate your transducer in an area of solid glass

The toilet wax idea is great!!! as even on an area where the glass is supposed to be solid the amount of air in the laminate will vary.

Shooting thru the bottom will cost some depth , so for inshore its fine.

If you want to contour navigate it might not get the deeper bottoms.

As FF and others mentioned, make certain you're not shooting thru a cored hull or laminate voids. Test it first before making the install permenant. I installed a high dollar 2kw unit in on the centerline in the bilge last spring, only to find out that it wouldn't shoot thru the keel (stupid amateur mistake!). Had to pull it out and reinstall at an angle on the hull (keeping the transducer level). Works fine now.

jeffnick said:

800 feet? My quest was to find a sounder that would read accurately in 1 1/2 feet. I don't care how deep the water is...I care about how shallow it is.

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I'm with Jeff on this although I do care how deep it is when looking for a spot to anchor.

There's a proceedure in the manual for determining a good location before permanently mounting the transducer, and using that proceedure, I went to the deepest area that was convenient to me, about 80'. I also tested the reading at top speed (13 knots). It was fine so I mounted it.

I don't think I've ever been in water more than 95' deep.

BruceK said:

.................... Eventually I fitted the transom mount transducer included with the unit, inside the bilge. I put a large volume of silicone in a piece of plastic drainpipe cut at the bottom to the angle of the bilge to get it horizontal at the top, put the transducer into the gloop, using a small level to get the foot level. It works ok but takes a while to get a "grip" on the bottom on start up. BruceK

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I suspect that's because the silicone (I'm assuming a caulk like product) is absorbing the signal from the transducer. Water (or antifreeze) will work fine because it conducts sound just as the water under the boat does.

If you want to glue the transducer directly to the inside of the hull (and have a horizontal surface available and no coring), you will do best with a rigid adhesive like epoxy, not something flexible (like silicone) that will absorb the transmission from the transducer.

rwidman said:

I don't think I've ever been in water more than 95' deep.

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Deepest I have been in was crossing the Yucatan Channel from the west coast of Cuba (Cabo San Antonio) over to Isla Mujeres, Mexico (in the sailboat, of course). It was right at 10,000 feet according to the chart. And my depth indicator just had little dashes in the digital display!

We have a cored hull so unless I want to grind out the core and at that point I might as well drill the hole which we have. Today's depth finders/transducers have better electronics than their predecessors which means more capabilities and better performance. We fish deep canyons so the ability read various deep depths in addition to shallow water is an added bonus.

But if our depth finder is ever reading 1.5 feet, we're in deep (or I should say shallow) sh.t!

"We have a cored hull so"

Many cored hulls are built so the boat has solid glass on the bottom.

Some taper the core out about at the LWL others go lower , core ALL the way to the keel is uncommon.

To make a light weight boat perhaps , but on a cruiser?

FF

Silicone or regular caulk works just fine if you keep the layer thin and as bubble free as you can. The power of the sounder is also a factor in the strength of returns when you mount in the bilge.

I have done several and all the returns are acceptable.

The mounting area also doesn't have to be very level either...depending on the beam angle of the transducer and you willing to accept a couple percent error.
It isn't the end of the world if you don't wan't to mess around with complicated mountings or don't need precision soundings.

FF said:

"We have a cored hull so"

Many cored hulls are built so the boat has solid glass on the bottom.

Some taper the core out about at the LWL others go lower , core ALL the way to the keel is uncommon...

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FF: I don't know what to say but Krogen 42's were built with the core to the keel from 1979 to 1993. From 1994 to 1998, which was the end of production, the core stopped at the water line. We had a Slocum 43 designed Stan Huntingford that was also cored to the keel.