Transducer advice – skimmer or thru-hull

[Sheppy]

I have an older model Lawrence chart plotter which came with an external 200KHz transducer (HST-WSBL). This has always offered good resolution and apparent good depth data but is prone to occasional inaccuracy from growth so requires regular cleaning – but the unit is a known quantity in that I know it works. The main problem is that it recently got broken, I suspect by friends accidently when playing at the rear of the boat. So rather than replacing like for like, I’m considering the shoot-thru-hull transducer (PDRT-WBL) instead. I have a 19’ sport cruiser and could install this either at the rear as before or possibly far more centrally.

I wanted to gauge response from anyone who’s installed the same or similar devices to make sure I won’t be losing accuracy or resolution. The manual states that the former transducer can also be mounted internally but I would assume the shoot-thru-hull version would offer better performance simple because it’s designed for the job?

Thanks

 

[PaulGooch]

Personally, i'd rather have the shoot through installation. I've had it before and it worked well enough.

 

[stefan_r]

I have surface mounted one and works fine. Not sure they work so well if you're using a fishfinder...but for simple depth mine (Raymarine) works fine.

 

[Sheppy]

Thanks guys for responding. It does seem like a thru-hull is the way to go but any more experiences would be greatly received - a decision has to be made soon.

I’m also interested in any installation suggestions too.

 

[gsturgeon]

Transducer

My boat when new, came with a "screw into the hull" type, I replaced it with a "through the hull" one epoxied in place for a fish finder. Last year to compliment the new plotter, I fitted a "screw to transom" one. To be honest I didn't notice any difference between any of them.

I suppose you could worry that those stuck to the hull are not mounted horizontally and underestimate the depth by a small amount but I really am only concerned with the last couple of feet.....

 

[PaulGooch]

I agree with sticking it down with epoxy. Some transducers are designed to be fitted at the angle of hull deadrise, but if not, they can still be fitted to allow for this.

Make a dam (plastecine, bits of wood stuck down with silicone etc), slightly bigger the the transducer and deep enough so that when filled with slow drying epoxy, the epoxy will be level, cancelling out the deadrise. When that's more or less dry, tip in a small amount of epoxy and press the transducer into it, giving it a twist to remove any air. It's important to ensure there is no air in any of the epoxy, which is why slow drying epoxy is recommended. Once dry, remove the dam.

 

[Red]

I have a Lowrance transducer mounted on the bottom of the transom - not a through hull. I went through the same dilemma as you but it was easy to fit, involved no through hull drilling and has worked perfectly even a high speed - 30 to 35 knots. The Lowrance transducer has a paddle wheel for the log, a temperature sensor as well as the echo part. It will also kick up out of the way if the boat needs to be put on a trailer. I am in favour of one less whole in the bottom of the boat.......

 

[Sheppy]

Thanks Paul. I hadn’t thought about making a level epoxy surface to mount the transducer on – excellent idea. I do have a small flat surface in the rear bilge but I fear it has a space under to allow water to flow into the bilge so it’s probably no good. I did think about removing the floor (actually quite an easy job in my boat, only about ten screws) and looking for a suitable location around the fuel tank area. But your suggestion would allow me to mount the transducer in the bilge but up on the deadrise angle out of the way.

Yes Red, it should be an easy installation on the transom; I am after all simply replacing the broken one. The existing unit is on the lower transom and has the cable running up the transom into the boat along with the various engine cables etc.. A fairly neat install but it broke easily because someone swimming at the rear must have accidently stood on it, so the plastic has broken. Neither install would require any holes in the hull – certainly something I wouldn’t want either.

I assume the thru-hull transducers are designed to power through the hull and some epoxy layers?

 

[Davy_S]

It would depend on what you require from your fishfinder, if it is simply depth and bottom contour, go for the thru hull. If you are a dedicated wreck finder/fisherman and are seeking shoals of fish and like to watch your weight sink down to the fish, then go for the transom mount, it will give far better resolution without any losses. horses for courses.