Topic: How to determine transducer/boat angle to bottom

[hannibal mike]

  It sounds easy but I am not sure how to measure or adjust my ducer angle to get best results.  Will a straightedge off the bottom of my 20' G3 jon show the angle that the bottom of the ducer needs to ride?  When the boat is on the water and I sit at the rear, does that effect the angle enough to cause problems.  I am recently unable to get a depth reading if I travel faster than 8-9 mph (it will read 1', 46', etc) and I do not get images as detailed as those posted at 2-3 mph with same chart speed.   I am mainly on the Mississippi River.

[RGecy]

Yes, getting the angle right can be difficult sometimes, especially if your bow rides high.  I would try to get a feel for the water line and make sure the transducer is parallel to it.  Placement is also very crucial and you have to try to find an area with the least amount of turbulent water coming off the hull.  You also need to make sure the transducer is low enough to get below any bubbles or turbulence coming off the hull.

If you could post some picts of your installation, we may be able to offer some more advice.

Robert

[freezerfiller]

You can buy a cheap angle finder from Home depot, or ebay that will tell you the exact angle that your transom is while your boat is in the water, then you can add or subract that from how it sits on the trailer..  I bought mine years ago, and it comes in handy for all kinds of projects.  Theres even an angle finder app, but I've never tried it.  I don't think hanging my phone over the transom while boating would end well.   Regardless of the angle, you will lose definition with increased speeds.

[hannibal mike]

Dang me, dang me.  Thats an excellent idea and I even have one that I use on my table saw blade to get the correct angle.  Ho, ho, ho, its off to work I go and now to do the math and adjust the 'ducer (which isn't too easy itself).  Any ideas why my depth readings jump around dramatically at speeds over 8 mph?  Wish it wasn'

[Humminbird_Greg]

I’m guessing that you are getting air bubbles under the transducer at 8mph or higher.  You can try lowering the transducer and/or angling the back end of the transducer downwards just a bit to try and get the transducer into “cleaner” water.  Lowering the back end of the transducer may not be the best thing for the prettiest Si sonar images though.  You’ve got an aluminum jon-type boat which is hard to get a high-speed depth reading on.  It may take many adjustments or even moving your transducer to another location to find a spot that works above 8mph or you may never be able to.  Keep in mind that the spot that works best for high-speed water depth readings may not also be a spot where the Si sonar will work best at (or vice-versa).

[hannibal mike]

Thanks, all of this is helping me understand.  Are there any other 'ducer installation locations than the transom?

[Humminbird_Greg]

Since the Side Imaging transducers have to be mounted in direct contact with the water, your only other option would be a Thru-Hull HDSi transducer.  I have not heard of anyone using one of these on an aluminum jon-type boat though.  I don’t think that it would work very well at high-boat speeds for your boat.