Transducer location question for SI on aluminum boat

[gitzitfish]

Here in my part of Ohio we have a bunch of 10hp limited lakes. I’ve always had an aluminum boat with a 9.9hp but I’m finally dressing it up. It’s a Sea Ark McBass 170 with a Johnson 9.9hp. It’s a nice boat that is decked out like a glass boat. It’s always had some cheapie hummingbirds on it and I’m going to put some nicer graphs on it. I have a Hummingbird 999SI in the garage that I’m going to mount at the console on a ram mount. Looking for the best location to mount the SI transducer on an aluminum rig? I shouldn’t have any turbulence or bubble trail problems I don’t think. It’s only about a 10 or 12mph rig at best. It’s pretty much a flat back boat with a modified jon boat hull. It’s rated for a 90hp but has a 9.9 direct bolted to transom with no jack plate. Where would be the best location to mount it to get good SI readings? I have the same unit on my glass boat which is at mechanic for some motor issues so I can’t even look at it to see where that transducer is mounted

[Bstandiford]

I have always run mine on the port side of the boat between the two outermost ribs to get the best readings. Just make sure there is no obstructions ( motor, livewell screens etc.) to block images. I usually fish from the port side and want the best images from that side. I have done several installations this way and have had great results.

[gitzitfish]

That’s pretty much where my transducer is now on my old 580gps hummingbird. I was thinking that would be a good location a2ay from motor and obstructions. I fish mostly starboard side and use my front trolling motor graph for fishing. Thanks for the help

[Bstandiford]

No problem! Hopefully you can get out and fish! I’m hoping this craziness will end soon and I can get back on the water!

[Wayne P.]

I have a Tracker with a 9.9 for limited HP lakes and electric-only waters. It has a stepped transom so I put the permanent mount SI transducers under the step so I don't have to trim out the motor to get clearance for the SI pulses and I place them above the hull bottom since I fish in trees and stumps a lot. I have placed them on either side of the outboard and they perform the same. Current have the MEGA SI+ transducer on the port side.

This is an ONIX HDSI transducer with Transducer Shield and Saver mount on the starboard side:



This is the MEGA SI+ transducer on the port side with custom mount:



AND when I am trying transducers for their performance, I use a former transom trolling motor mount/shaft to get it below the hull bottom away from cavitation. This has a MEGA SI transducer attached:

[gitzitfish]

I don’t have the stepped hull but that is a very good idea on the testing mount. I believe I can fashion something up similar to test

[SLYDoggie]

I think your main issue for side imaging in your setup will be the motor blocking the SI signal. You can tilt the motor up while fishing so that it provides an unobstructed path for the SI beam or you can install a second transducer and have each provide one only one side of the beam. That may be overkill for your purposes but it may be the only way to get a good signal on both sides of the boat.

The other thing I've always heard about aluminum boats is to make sure you avoid putting the transducer behind any rivets or anything that could cause additional turbulence.

[Wayne P.]

I think your main issue for side imaging in your setup will be the motor blocking the SI signal. You can tilt the motor up while fishing so that it provides an unobstructed path for the SI beam or you can install a second transducer and have each provide one only one side of the beam. That may be overkill for your purposes but it may be the only way to get a good signal on both sides of the boat.

The other thing I've always heard about aluminum boats is to make sure you avoid putting the transducer behind any rivets or anything that could cause additional turbulence.

Yes riveted hulls and some of the new hulls have a welded trim tab that have to be dealt with.

[Bstandiford]

Yes riveted hulls and some of the new hulls have a welded trim tab that have to be dealt with.

My new Weldcraft has those trim tabs at the bottom of the hull. I mounted a “5 PVC cap like you see on the top of plumbing trucks ( only with the smooth finished end) just above the tab. It gave me the clearance I needed and with the power tilt the motor is out of the way as well. Another benefit is if I had to go with a different transducer I’m only drilling into the cap and not the boat.