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Looks like i will have a choice between getting a transom mounted or shoot through (no hole) transducer. What are the benefits of the two? I already have a transom mounted one, so install will be a snap, but if there is a reason to move to a shoot through, Its a great time to do it.
BTW Boat is a parker 18, fishing in on chesapeake bay.
There is no reason to move a transducer to shoot thru the hull if the current transducer is giving you readings at all speeds. If it's not...and you're losing bottom at 20mph or so, then moving it to thru hull makes sense. I love my thru hull setup...and I now have a "spare" transducer on my transom, just in case the one epoxied to my hull in my bilge stops working.
I am losing the bottom at about 25. i am using this as an excuse to upgrade from my six year old eagle. I'm afraid ill have to buy one or the other style transducer then install it, so i'm hoping folks can steer me in one direction or another.
you might be able to use your current transducer as a shoot thru the hull. I know that Garmin transom mounts work very well as shoot thru the hull units. If your current transducer is easily removed, you could try it....place your current transducer on a baggie filled with some water on you hull (in the bilge) and brace it somehow....see how it reads. Of course speed and temperature won't work too well inside the hull
I have the same boat. I switched from a transom mount transducer to an Airmar P79 shoot through this year. I like the shoot through much better - I do not lose bottom even at WOT, and I "seem" to have just as much detail/descrimination on the fish-finder (although I am generally not in water deeper than 100' or so).
The added benefit is that you can patch the screw holes from the transducer in your transom (the Parker's transom is wood, and I was concerned about water intrusion over the long term).
My old transom mount had a temp guage, which I liked, so I purchased the temp probe accessory (which is about the size and shape of a quarter) and glued it my transom. My fishfinder is a Garmin 240 Blue.
Good luck. I think you'll be pleased with the change.
Paul, thanks for the response. I am curious about a couple things.
where and how did you mount the transducer in the bilge, and why did you choose the blue over the regular 240?
I like the garmin, but don't think i see down to 1500 feet. That being the case, does the duel frequency of the blue have any other advantages? I don't mind paying for it if it makes sense, but i would hate to pitch money when its not needed. The bay does not get that deep for me.
the transducer is mounted in the bilge, on the starboard side about 2" or 3" from the transom. It is probably an inch or two starboard of the keel.
I bought the 240 Blue because it is a dual frequency machine, and the P79 is a dual frequency transducer (to my knowledge, it will not work with a single frequency unit such as the 240). I obviously don't need to see particularly deep either, but the extra power of the 240 Blue is probably an asset in any event, as you need to shoot through the fiberglass hull. Let me know if you have other questions.
I have never had good luck with "shoot thru" hull transducers. Some here are confusing these with "thru hull" transducers which are totally differant.
I am building a new 36 Concept and the owner of Concept Boats strongly suggested to go with a "transom mount" over a "shoot thru" transducer. My hull is solid glass and a "shoot thru" should work but they never seem to.
Also my friend has a Path Finder 22' and his "shoot thru" never worked correct so he changed to a transom mount and his fish finder works perfect.
For what it's worth, I am talking about a "shoot thru"; not a thru hull - no confusion. The tansducer is an Airmar p-79, and it's OEM for Garmin, Furuno, and many others. When compared to a transom mount (as opposed to a thru hull), my experience is that this transducer is far, far superior. I had all kinds of trouble keeping a fix on the bottom at speed with the transom mount, notwithstanding numerous attempts to adjust the angle, etc. The transom mount also tended to collect marine growth even though it was treated with anti-fouling paint. Finally, it required drilling a hole in the transom into the wood core, which I did not feel comfortable with.
The performance of the P-79 for me has been flawless. I haven't lost bottom contact since I installed the unit, and I (personally) can discern no difference in fish-finder performance. I am excedingly pleased with the unit. In my view, for an 18 foot center console boat with a solid glass hull, it is the way to go. I won't go back to a transom mount.
Paul,
Do you have A temp guage on you FF? If so, how did you run your probe. I have seen two versions, one temp probe that is built in to the transducer, and one that is part of a speed wheel. personaly i will pass on the speed wheel, as I run a gps, so I assumed to the transom mounted ducer with temp probe is the way to go. Bottom line is I have too much time on my hands, i just need to get the unit and go.
BTW I am up on the severn , and plan to stick to the river and bay bridge area, but i will make occasionsl trips tp Virgina beach, so i need to build in the ability to look deep.
Chris:
go to the Garmin website, and look at the accessories for the 240 Blue. There is a stand-alone temp. probe, model number 010-10225-00. It is a flat piece of metal, about the size and shape of a quarter. I 4200'd mine to the transom, below the waterline, and ran the small cable thru the "cable run" (for lack of an official term) from the bildge to the console of the Parker - probably the same way the wire from your transom mount currently connects to your fishfinder. It is a simple and straightforward installation, and it works great.
shoot through vs transom mounted transducer? 
