Transducer Options
 

Hello all, I'm new to the world of thru hull transducers and deadrise. I'm considering purchasing a Airmar B150M for my 89' 20 Seacraft and have options of 0, 12 or 20 degree ducers. Not sure how far from the transom it should be mounted and what the deadrise is at the preferred mounting location. Any suggestions would be greatly appreciated.

If you have an iPhone you can get an angle finder app and place it where you want to put your ducer and it will tell you the angle at that location. Move the phone to different locations fore and aft to get it as close to either 12 or 20. Mine is on the inboard step about 3 feet forward of the stern. I believe I went with the 20

That's sweet Chance. I'll see if I can do that in the morning. I appreciate the tip.

After trying every imaginable transducer/location/mineral oil/witchcraft, a far more knowledgeable member of this forum suggested I simply lay the transducer in the bilge, facing down, in the center/keep location. Almost too simple and had most anyone else suggested it I'd have rolled my eyes and walked onward.

It worked PERFECTLY!

(thanks Joey)

Mark, are you saying there's no need to install the transducer either thru hull or transom mounted? No cables routed outside the boat?
John

No, it shot through the hull just fine - no holes drilled in anything. After all my fussing with the various fancy transducers, I went back to the one that Garmin shipped with my bottom machine and it worked great, regardless of speed. (I presume a Furuno would work similarly)

I realize this method may sound rather ghetto, but it worked great. The wire came down from my electronics and entered into the bilge under the console. The actual transducer ended up sitting about 18" forward of the transom and no holes were drilled - anywhere. Although I had previously affixed the tub/cup that the other transducers were supposed to mount to, I gave the "toss it in the bilge" method a try on just one day. After that one day trial run I managed to unglue/remove that cup of mineral oil and never looked back.

That works...but if you want water temperature it's got to be in the water....

That being said, mine is a 20, thru mounted approx 18 " forward of the transom on the first step next to the center line.

That is where it goes. I mounted an SS 264N in roughly the same location. 20 degree is what you want. Being I went with the much larger 264 I had to cut nearly a 4" hole. Scary at best but the best thing I have ever done to enhance my scope's abilities. I have perfect imaging at any speed and condition that some on here can vouch for.

Ken's Ducer
 

It works great and reads clear even when Mel has the throttle mashed to "YODEL".
signed The Mango Maurader
PS - 20 degree unit, 18" ahead of the transom 8 - 12" off the keel seems to work well
on the Marstackie too.

Yepper!! I have the 1000w B164 20 degree and it's a very good unit. However as Moose said watching a 3 3/4" hole saw drilling through your hull really kicks in the pucker power!!

Depth
 

DonV,

How deep are you reading until your unit goes blank?
Running the b164 also, with the garmin 740s. Getting about 800. Was hoping to drop on some rosies :mad:

If you choose a "shoot through" transducer without temperature, what is the downside to not having that data other than determining "shrinkage" factor?

I have the Raymarine DSM300 module with my old clunker C120. I have trolled at 1400' and seen the contour of the bottom very well, that's as deep as I've had it. Can't say I would be able to pick out a swordfish or anything like that, never tried to zoom in to the bottom for rosies or the really deep guys.

Up to 30% loss signal loss on transmit and receive. Not a real problem in shallow water up to 150, but definately a problem in deeper water with units under 1000 watts. I once had it both ways on a Paramount superfish and ran a 200/50 glued inside. I did'nt know what I was missing until I transom mounted it. The biggest return issue when it was glued inside was the deminished fish show return.

Transducer mounting location
 

Still rigging my 23 CC and about ready to install a pair of Garmin GT51M-THP transducers. My concern is the best hull location. They seem really large for a 23' boat . I like the second step location but my concern is will this location effect the water flow to the prop with a single outboard mounted on a twin Hermco bracket?

If you mount outside the first step, the water will be aerated, no bueno.

Sell one and mount a single dead center of the keel. In all reality you could of gone with a transom mount and mounted it right next to the drain plug. That is where I mounted mine and it doesn't bother the motor whatsoever. Your bracket is much longer than mine so there would be no issue. I wanted to go thru hull as well but I didn't want to cut the center stringer but that would be the best place and I will make accommodations on my next build.

If you go with both thru hulls you will likely have to go with fairing blocks to get them low enough in the water.

The transducers come with fairing blocks that can be cut to the angle of the dead rise. I would be concerned with the first step mount in that it may cause cavitation. Shine said outside the first step becomes aerated. I also have reservations about cutting the center stringer. I may be forced to go with a transom mount if I can't figure out how to make these work. Thought it would be nice to have down view, side view, and chirp in one set of thru hull mounted transducers. Thanks for your input.

You still have all of those with a single transom mount and with your bracket it will have a clear view to both sides.

Moose. Do you think you could have mounted your Gt51 half way up the last panel?

Last panel being 1st v or closest to bottom. Duh.

So half way up the step closest to bottom ?

I like the transom mount but my only concern would be routing the cable with it mounted under a 30' set back bracket.

30" set back. I hate proof reading.

Routing cable is no big deal for me. Just trying to confirm gt51 can be about 6" up off flat spot on keel. I beach boat a lot and would like to keep it up if I can.

I am no expert on the matter but it seems that if the transducer remains in the water at all speeds and is within the first step of the hull it should work fine.

Yes, I could of and have on a GT 52 I was testing. What I have found with these sidescan transducers is the lower the better as they need the both sides in clean water. I had issues with one side not getting clean water, or as clean a water as the low side at higher speeds. The 51 mounted dead center give the best results by far and I have good returns at 30+ knots on sidevu. On my next build I will mod the stringer and go to a through hull on the back end of the keel but where I have it now is great.

It's really not about being in the water but how clean the water is moving around the ducer. The higher up you are and closer to the strake the more chance of aeration at higher speed. Also consider the angle of the hull in front of the ducer. Regular transom mount ducers shooting down are not near as fussy about clean water across the side but the sidevu ducers are. If you're getting good returns to each side then all is good but if one side is better than the other a keel location works great.

As far as beaching goes... that would be an issue to consider when mounting but I have my trim range set to not let the back of my boat get into shallow enough water without my lower unit protecting it.

Thanks all. Sorry for the hijack. I will mount 1/3 up the bottom panel away from keel on port side and report back. I will be sure to leave just adjustment for down. I won't be able to check for clean water under a bracket :(

Please report back your findings with your mounting locations The Hermit. How did you decide to run the transducer cable under the bracket?

I found out that the vender for the Thru hull pair of transducers will allow me to return them with the purchase of another style transducer. The only other option that I know of with side view capabilities is the transom mount. Looks like I will have to make this design soon in order for them to accept the return. I am thinking about returning them for the transom mount and install it similar to Kmoose and the Hermit's installation. I really wanted to make the thru hulls work but there are too many unknown factors in this application (aeration/cavitation).

Great info as always!

Moose, which unit will you use for your next project to go through the keel?

Jamie

On my next project I will bridge the stringer and mount a gt51 TH right on the flat part of the keel. The only issue will be potential damage but I will be willing to deal with that.

Returned the 51s today and bought a B75H 20 degree. Fish shallow water less than 100' and figured I could always add down and side view later with a transom mount.