Fish Finder advise

[Mike_R]

Hello

I mostly fish west coast Haida Gwaii with my 19' aluminum outboard driven boat. I presently use a basic Garmin sounder with a transom mount transducer which performs well enough but loses the bottom when running at speed. I would appreciate advice on purchasing a stand alone sounder and am wondering whether a thru-hull transducer would solve my problem. My budget is $800.

Thanks

 

[Dirtguy]

i have owned a few different finders and they all lose the bottom at speed, in for answers

 

[Bait Ban]

Can you post photos of your current transducer location? Thru hull may or may not track bottom at speed, it's all about location, output power of the sounder and quality of the transducer.

 

[Seafever]

When you say "speed".......how fast are you talking?

 

[Mike_R]

Here is a photo of the transducer.

I lose bottom at about 14 knots and above.

 

[Barnacle Bill]

Looks a bit low to me. Maybe try raising it up until it is just about 1/4-1/2 inch below the transom.

I have mine located like that, and do not lose bottom at over 30nmph and over
300'. Good luck. .......BB

 

[LowTide]

You may have mounted the xducer too far below the transom. It may be that you could check your installation manual, online if you have to. Another issue could be the "basic" nature of the unit.

 

[Seafever]

That trim tab is probably throwing off a lot of squirly water when your up and running.......and starting to gain speed.......could be just enough to mess up the transducer reading. And you have the engine and cav plate pretty close on the other side....which will produce that kind of water too....

Transducers do not like roiled squirly water with lots of bubbles in it. And the faster you go the more it's going to get like that.

Plus the engine could be throwing off some electrical interference at speed.

It also looks like the transducer is not sitting at the same angle as the bottom of the boat. The boat hull has a degree of angle on it but the transducer does not...

You want the transducer so that half of the transducer bulb (bottom half) is below the bottom of the hull in front of it if you lined it up dead on even.

The way it sits on your hull that might be difficult to accomplish.

Were I you , I'd be taking a deep interest in a through-hull transducer. But it would still have to be mounted inside the hull so that the transducer is pointing straight down....not sitting on an angle....

 

[LowTide]

You may have mounted the xducer too far below the transom. It may be that you could check your installation manual, online if you have to. Another issue could be the "basic" nature of the unit.

 

[Canso]

That a bad picture angle to see the hight. I would try mounting lower. Put a straight edge on the bottom of the boat. The transducer needs to protrude below the hull.

Look down at the back during speed, it should be clean green water coming from the transducer no white water.

 

[Bait Ban]

I'd put an Airmar P319 thru hull in. Just the thru hull version of a p66/ p79. Looks like a tight fit between the motor and the trim tab, ruling out Transom Mt. Better to upgrade the transducer, than to buy a $800 midrange fish finder with a cheap transducer.

 

[codfather]

Mike_R, the angle of the transducer is to flat. The back end needs to go down one notch. That way it shoots ahead a bit and bounces back before the boat passes by. I can go 25 mph in 400 feet and get a good picture of the bottom.

 

[finaddict]

Location on the stern looks good. I think you are far enough away from both motor and trim tab to not cause too many issues. If you are thinking of moving, I think it looks like you could move it more to the center of the boat on that mounting bracket.

I would suggest that the issue at speed is water column quality. You are likely sucking a lot of air under that light aluminum boat at speed and the air under the transducer is creating too much "cavitation". I think Codfather has a point about the angle as your transducer appears to be pointing too far aft. I also agree that too high would be a more likely issue than too low. Too high will also put the transducer in an area where bubbles will "back-eddy" behind the boat and create problems.

I also agree with Bait ban. Transducer quality and power are THE most important issues in depth sounders

Quick question.... Is 14 knots about where the boat starts to plane?

 

[codfather]

Mike_R, here is a pic I took yesterday. As you can see I'm going 27 mph in 439 feet of water.

 

[naknekm]

If you go with a thru hull, make sure you use a stainless steel transducer with your aluminum boat and not bronze.