I recently bought 18’ 1985 Champion boat, the transom is stepped like Ranger or Skeeter boats. The back tapers in, which doesn’t leave any space that is not behind the stepped part. Does that step interfere with water flow that would cause the transducer to not read the bottom or fish accurately? Where would be the best place to mount a transducer?
I would look for a place to shoot through the hull. If there’s already a locator unit on the boat you could follow the wiring to find where you need to mount the new transducer.
This is how mine is mounted on my ranger. I’d never take the loss in sensitivity to shoot through the hull.
I have done the same with my stratos. Isecond the sensitivity comment.
I can still see schools of Ciscos through the hull on my boat, you just have to turn up the gain.
But I guess it could really depend on what you’re doing. On bass boats a lot of guys are just looking for depth and structure and then look for weeds etc on their bowmount.
I’m currently running a Humminbird 981C and a cheapo Garmin. I use the Garmin while running (thru the hull) and the Humminbird when off plane. I have the Humminbird super sensitive Side Imaging Transducer mounted to my jack plate where it’s nice and clear from danger and I don’t have to drill holes in my hull. 
This spring I will mount another Humminbird transducer to shoot through the hull. So I will switch between transducers depending on function.
Some bassboat manufacturers make special areas specifically for shooting through the hull and your sensitivity loss is minimized in those locations by hull design. On an ’85 Champion? Probably not but worth a look.
Back in the day I had a paper graph shooting through the hull of my boat and it looked as good as anything I’ve ever seen.
Also, if you look at the transducer picture above, if that transducer falls for some reason, when you launch your boat, it will get ripped right off your boat and possibly strip those holes in the hull. Similar things have happened on my dad’s aluminum boat.
I don’t agree with the loss of sensitivity if you have a high power unit. With my 4000 watts of power I can see a jig in 30ft of water. The only problem is if the transducer goes bad it is a pain to change.
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I don’t agree with the loss of sensitivity if you have a high power unit. With my 4000 watts of power I can see a jig in 30ft of water. The only problem is if the transducer goes bad it is a pain to change.
Go to lowrance’s website read the FAQ’s, call and ask them they’ll tell you to expect around a 15% loss in sensitivity. This is also why they make through hull transducers.
Nick’s right, you will undoubtedly lose sensitivity, the question is if you lose too much sensitivity. In most applications you will likely have enough gain to recover the 15% loss. I’m not saying it will be perfect but more than likely good enough. With the 4000 Watt system you probably have way more gain than you would ever need.
Here are the pros and cons according to Lowrance:
Shoot-thru-hull transducers are epoxied directly to the inside of fiberglass boat hulls. The sound is transmitted and received through the hull of the boat – but at the cost of some loss of sonar performance. (You won’t be able to “see” as deep with a shoot-thru-hull transducer as one that’s mounted on the transom.) The hull has to be made of solid fiberglass. Don’t attempt to shoot through aluminum, wood, or steel hulls. Sound can’t pass through air, so if there’s any wood, metal, or foam reinforcement, it must be removed from the inside of the hull before installing the transducer. Another disadvantage of the shoot-thru-hull transducer is it can’t be adjusted for the best fish arches. Although there are disadvantages to a shoot-thru-hull transducer, the advantages are considerable. One, it can’t be knocked off by a stump or rock since it’s protected inside the hull. Two, since there is nothing protruding into the water flow, it generally works quite well at high speed if it is mounted where a clean laminar flow of water passes over the hull. Three, it can’t be fouled by marine growth.
True I suppose it all has a lot to do with how you fish, I think Bass fishing wise, I could probably handle the loss if I were running in stumpy areas and fear knocking off my transducer all the time.
Walleye fishing I personally wouldn’t give up any, to each their own. 
Thanks for the help.
I put the ducer on, now I just have to see how well it works.
What year Ranger is this? I have a 2005 and at high speed I loose it all and mine is mounted there too? Any advice?
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