posted 06-30-2009 03:14 PM ET (US)            

Your unit may reset quicker and you probably wont be backing as often, just letting you know. Garmin transom mount transducers run about $110 here in the NW. My thru hull Tug unit cost around $2k including pro install. I would think the install and seal factor whether steel or glass would be similar. Steel may be easier.

posted 06-30-2009 03:52 PM ET (US)            

Through-hull transducers are prefered on displacement hull boats where there is no sharp line of departure from the water on the stern, and where aerated water under the boat amidships is not a concern.

The only other reason for using a through-hull instead of a transom mount is to keep the transom clear of potential snags for fishing or working lines, and to protect it from the feet of swimmers or divers re-entering the boat over the transom.

posted 06-30-2009 05:31 PM ET (US)            

quote:

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I can think of no reason you would ever want to install a through-hull transducer on a planing hull, outboard powered boat. The transom-mount, if installed correctly, will perform better in every regard.

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quote:

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The only other reason for using a through-hull instead of a transom mount is to keep the transom clear of potential snags for fishing or working lines, and to protect it from the feet of swimmers or divers re-entering the boat over the transom.

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I think you defeated your own argument with the second quote. Those are just a few reasons for a thru-hull transducer

I can think of several others in fact. Modern, thru-hull transducers are designed to hold bottom at much higher speeds than traditional, transom mount transducers. In fact, many sonar devices will state that in order to obtain high speed readings, thru-hull or in-hull transducers must be used. All you have to do is read the literature provided with them to determine this.

In addition, a thru-hull transducer is far less likely to be damaged from running over debris, or when you may travel in shallow water, or beach your boat to allow kids to play. Once the plastic clip piece contained on most transom mounted transducers is damaged, the transducer must be replaced. For me, that has meant a 2 new transducers in the last 5 years.

posted 07-01-2009 11:37 AM ET (US)            

I guess I should have pointed out that those are non-issues for Whalers. Having exclusively outboard propulsion, the increased risk of snagging caused by a transducer is really nothing compared to the fact that the engine hangs off the back right in the same area.

I consider the fairing block and transducer on my trawler to be at much greater risk for damage from running into debris or aground than a flip-up transom mount unit. What's worse, damage to a thru-hull could hole the boat.

posted 07-01-2009 12:06 PM ET (US)            

If you're worried about little feet standing on it, don't. Most transom mounted transducers can be flipped up against the transome when not in use, thereby removing the temptation to step on it.

I just installed a new transducer on my Outrage. It cost $100 (Garmin) and gives me a decent picture of the bottom down to about 350 feet at 20+ knots and finds the bottom at about 1,000 feet at about 8 knots.

posted 07-01-2009 01:01 PM ET (US)            

Logically, the transom mount is the best location for a outboard boat because that is the location of the least amount of turbulence in either direction. Again, the thru-hull is relative to how often you will create turbulence...and I cant confirm whether a outboard will even create that much turbulence. There is a lot of turbidity in my area (Volcanic sediment) and I work in shallow water. Take my advice with a grain of salt...but, I do know, once the Garmin 545s kicks out, it takes forever to reset using default gain.

Ive owned a 22 Outrage as well. Personally, knowing the foam issues, Im not so sure a thru-hull mounted transducer is something I would desire as owner or potential buyer unless it was professionally installed. One of the worst problems with classic whaler hulls is water intrusion thru the rotted drain tubes, will your thru-hull become another water intrusion liability down the road? My steel Tug does not shake and wobble that would loosen up the transducer in rough water or even a hard landing alongside a barge tow. Do you launch often or moor the boat? Does the glass and foam contract and expand a smidge due to sudden air/water temp changes when you launch? Does the hull flex a little when you hop over a ship swell or rough water? Does this sound like I am trying to talk you out of thru hull installation, hehe, well, I guess I am but I make no claim to be a glass/foam thru hull installation expert.

posted 07-02-2009 01:05 PM ET (US)            

The potential benefits of a through hull transducer are vastly outweighed by the risks created by modifying the hull in that way.

posted 07-08-2009 04:30 PM ET (US)            

A Boston Whaler is NOT a foam cored hull. It is a foam hull, lined with a thin layer of fiberglass. In a traditional foam cored hull, the foam itself does not provide much, if any, structural rigidity. The fiberglass provides the strength, while the foam is merely a filler that adds thickness without adding too much weight. In a unibond hull, the foam provides the majority of the strength, while the fiberglass is just there to keep it dry and hold it all together in one piece.

The most notable difference between a traditional Airex cored hull and a unibond hull is the thickness. In most locations, a Boston Whaler hull is MUCH thicker than a cored hull. This thickness generally prevents the simple method you describe of drilling a hole and inserting a through-hull transducer fitting. A typical cored hull might be 1.5-2" thick at most. A Boston Whaler hull, near the keel, where you would want to install a transducer, might be 6-12" thick. In order to install a transducer in that boat, you would likely need to remove much of the foam, and then glass-in a well into which the transducer could be installed, while adding additional thickness to the exterior of the hull, over and surrounding the footprint of the well, feathering it out to spread the load to the surrounding foam. A skilled fabricator with experience and training specifically for working on unibond hulls could probably do this successfully. A backyard DIYer most certainly could not. In the best case scenario, the end result would be ugly on the inside and change the hydrodynamic performance of the boat on the outside. All for what? One less thing to snag your fishing line on?

Factory installed through-hulls, like the drain tubes, typically don't create problems because they're factory installed. Extra glass applied to the laminate while it is in the mold, providing the additional strength necessary without affecting the hull shape. In many cases, in the area immediately surrounding any hull penetrations, the manufacturers forego any foam, and simply laminate it as solid glass. This is true of foam cored boats, and I would not be surprised of Whaler did the same thing. Nonetheless, hull penetrations, including drain tubes on classic Boston Whalers, are frequently a source of water intrusion. Hence why there are so many threads on CW about replacing them.

posted 07-08-2009 08:15 PM ET (US)            

The hull is about 4 inches thick at that point. We had a pro do the glass work. After drilling holes through the hull, we took an allen wrench and bored out an inch of foam and the cavity was filled with glass mash for strength. Also, the installation point was in the rear center well. I could email you a picture of what we did.

posted 07-08-2009 10:03 PM ET (US)            

I am not married to the idea of a through-hull installation, but not for the inaccurate or exaggerated descriptions of installation issues described in this thread. I have designed a installation procedure that piggy-backs the technique recommended for cored hulls that someone with modest skill could accomplish and be assured the hull would remain leak-free and sound. This site is full of talented do-it-yourselfers who often demonstrate ability beyond those of repair shops. For many here, tackling a job like this would be second nature.

Essentially, you drill a 3 1/2" hole in the inner hull that travels down through the foam but not through the bottom. From the underside of the boat, drill a 2" hole centered in the 3 1/2" cored hole. So now you have a hole in the boat; 3 1/2" in diameter all the way down to the bottom where a 2" hole penetrates through the hull bottom. Slip a 2" piece of PCV or other rigid material of 2" diameter up through the bottom and sits higher than the floor. Lubricate or wax coat the PVC pipe. Mix up a batch of West Systems Epoxy with structural fillers and pour it around the 2" PVC pipe up to a level even with the floor. Allow it to set and remove the PVC pipe. You have now created a nice, clean structurally reinforced hole of precise diameter as the transducer. You may need to drill out a bit of the new Epoxy from the top if the stem on the transducer is shorter than the depth of the new hole, but doing so will not compromise the new casting provided any new removal of Epoxy is less than the diameter of the new casting, which it should be. No radical glass work. With some pre-planning, this could be done in an hour and a half or so. Here's a picture of what the install might look like.

http://s299.photobucket.com/albums/mm314/77SETransAm/?action=view& current=Thru-HullX-Ducer.jpg

My hesitation comes with the possibility of the unit not functioning properly or otherwise needing to be replaced because of obsolescence or a change in equipment. Any replacement unit would need to be of similar size and design. A transom mount transducer is changed out much more easily. I'm just getting tired of doing it when the little plastic piece that holds the transducer in the down position breaks, or the unit itself is damaged from being so exposed.