Transducer mounting problem?

[grey2112]

Just recently bought a Humminbird 1198c SI combo unit - does Side Imaging, Down imaging, and is a GPS.
Well, I think the transducer may not be mounted correctly. Here are the issues:
1 - I see some definite splash and spray coming off it when I'm going any speeds above 10 mph - it is especially noticeable when up on plane
2 - At various times the depth reading goes whacky - like saying I'm in 120 feet of water when I'm really in 3 or 4 feet of water. I have to come off plane, slow to a stop, and wait about 5 seconds for it to read properly again.
3 - When going at speed sometimes the sonar reading will get all weird - instead of showing contours and bottom it will show a bunch of "noise" and clutter.
4 - The side imaging on the port side is very limited - I think this is due to the side beam on that side hitting the lower unit of my motor - I suppose I can't do much about that short of either getting a jack plate, or not relying on the SI unless I am using my trolling motor and have the motor tilted all the way up and out of the water.
I'd really hate to have to get a through-hull transducer, but if I can't solve these issues I may have to.
Here's some pics and details of my current transducer mounting:
1 - From the outer edge of the prop to the port side of the transducer it is 10 inches.
2 - From the dead center of the prop (as well as dead center of the boat) to the port side of the transducer it is 17.5 inches
3 - When looking at the rear bottom of the transducer, it is 1.25 inches between the bottom of the boat and the bottom of the transducer on the starboard side of the transducer. It is .5 inches on the port side from the bottom of the transducer to the bottom of the boat.
4 - From the starboard side of the transducer to the first strake it is 7 inches. To the next strake it is 14 inches, and to the final curve/bend/outer edge of the boat it is 18 inches.
I have a 12" - 14" draft on the boat with a 19 degree deadrise.

Pics:

 

[grey2112]

Re: Transducer mounting problem?

 

[Texasmark]

Re: Transducer mounting problem?

If you move it outboard about 6" and line it up with the lifting strake there you can solve part of the high dead rise transom problem. It's flatter there. Don't move it out past it as the outboard side of the strake is usually full of bubbles and you don't want that.

Even though the thing is bullet shaped it's still down in the water and will no doubt will generate spray. I used to raise mine up and slightly tilt it so that the front was just at or slightly above the hull so any water going past it would go under or to the sides. It has to be in contact with the water to get a return so you need to ensure that it is mounted as I said to keep the bottom wet. The actual transducer device is not that large and probably mounted around the center of it so you aren't going to miss anything with the front up a little and the angle won't amount to that much. Your beam width probably will cover any angle imposed by a slight tilt.

If you pass over waves and the sensor becomes airborne, you will loose signal and it may have to recapture it causing the funny reading.

At planing speeds and beyond, expect interference, fish that aren't fish, as that is caused by air bubbles.

Ditto on your engine blocking some of your side looking capability.

I think everyone on here uses 3M 5200 marine sealant to seal holes in the glass.

HTH,

Mark