Re: hds strucute scan
Yeah, 3" sounds about right although you might be able to get by with a little less. If you get it too close to the prop rotation, it will cause the prop to ventilate on that side and that side of your boat will rise up in the air at speed.
The Prop on an Alpha is more than 18" aft of the Transom.
As long as the Transducer is outside of the AV Plate, it will not effect the water flow into the prop.
If the Transducer can not see below the keel, it will be looking through all the bubble filled water behind the transom and the picture will be noisy to that side.
Get it as low as you can and just to the side of the drive AV plate and you will be fine.
The 3 inches to the side of the prop warning would be more applicable to an inboard engine where the rudder can direct disturbed water over the transducer if it were positioned behind the propeller.
With an I/O the Prop is in front of the Prop, so the issue is the transducer disturbing the prop rather that the prop disturbing the transducer.