SI Transducer mount

[Steve Johansen]

Hi guys,



I just bought a Humminbird 798si unit and the instructions on mounting the transducer are a little vague.



In one paragraph it says that on a stepped hull you may be able to mount it on the transom, but you will have to make sure that is somewhere that will keep it in the water at higher speeds or it won't read properly. Then in a picture it shows it mounted on the transom, well above the step in the hull! I don't get it.



I have a stepped hull on the back of my 1993 190 DC and I just want to know where the BEST location for the transducer will be. I would also like to use the holes in the 'top' of the step that were used for the mounting of the Bottomline speed sensor/transducer that probably came on the boat from the factory.



I was hoping to make a bracket that would be able to use the original screws above and make a 90 degree bend in it to mount the Humminbird mounting bracket.



Do I want the transducer unit itself below the bottom of the boat? If yes, by how much?



By knowing that I will be able to fab a bracket that will locate it in the correct position.



Any help or ideas would be greatly appreciated!



If I need to I can take a picture of what I have to work with and post it here.



Thanks, in advance!



Steve

 

[Dan J.]

You don't have a true stepped hull on a '93 190. The transom goes straight down to the pad edge, right? A stepped hull is a built in offset like the Tracker Revolution Hull and most Rangers with extruded transoms. "Stepped" puts the engine up and back from the hull's pad in cleaner, less turbulent water.



You want to get your transducer to the lowest point on the hull, between chines, just off one side or the other of the pad (drain plug) area. Use the keel offset feature to adjust your graph reading to the actual surface to bottom measurement. Good luck!

 

[Jim B]

Another thing to think about is the speed of the boat. If its a fast one the plastic bracket that comes with that model could break if you go up over 50 if its in the water.



What i did with mine is i glued one in the hull and got the y cable that they sell and mounted the si transducer up on my plate so when im running at speed its out of the water and when im at idle its in the water reading. it works pretty well that way.

 

[Dan J.]

Ditto Jim B on the thru hull. If you have the room to glass a puck inside the bilge area, you will have little to worry about. Done right (without any bubbles in the epoxy) the signal loss through the hull is negligible and the performance is most durable. Good luck!

 

[Steve Johansen]

So looking forward along the bottom of the boat, how much of the transducer should be below the bottom of the boat? I think that I got it in a good area now, with about a 1/4 inch of the transducer below, exposed to water passing by at speed.



Sound good?



Thanks!



Steve

 

[Humminbird Greg]

Hard to say if that

 

[Aroldo Hernandez]

A friend of mine put his on the outside on the pad for the SI and ordered a cable to switch to his inn hull whick he already had from his previus humingbird unit. When his on plane he uses the inn hull ducer and not the SI ducer.

 

[Dan J.]

Greg answered it well (of course!! ), so don't try to get too hung up on an exact location or angle until ran thoroughly and adjusted, if necessary. The main thing is to have it in a fairly level position to the water's surface up and running, which it sounds like you have. Keep your skimmer tight enough to keep it straight on plane, but loose enough to swing up should you hit some debris. I can't really say there is one specific right way or place to mount. As soon as your hull weight changes, so will your pad/puck surfaces slightly. (Don't sweat that because once you get a good reading you should continue to do so even with the weight changes. ) Once you get it mounted to an area free of turbulence with the skimmer face below the surface on pad, you're 99.5% done! Enjoy!!