Catalina 30 Depth Finder Problem

[jim.m]

Hi All,
Last season I purchased and installed a Raymarine DST-800 transducer to replace original knot meter and depth finder. I put it in the original depth finder thru-hull. This was probably too close to the wing keel because the depth always shows up as 2 feet The old depth finder didn't have this problem. Anyone else have this problem? Any ideas for a simple resolution other than remounting it somewhere else on the next haul out?
Thanks in advance,
Jim
Odyssey
Catalina 30 1988 Wing Keel/Tall Rig

 

[jssailem]

The unit you purchased has a narrow dead rise angle..

Deadrise Angles

8-15°

You want to manage this so that beam misses the keel. Do you by chance have a wing on your keel?
The signal being transmitted to the bottom by your transducer has a narrow beam.

Beam Width

13°

 

[jim.m]

Yes it is a wing keel and I'm pretty sure the depth finder is just bouncing off the wing. Odd that the original depth finder didnt have this problem. Everything is mounted pretty firmly so I can't tilt the beam. I was thinking about rotating the transducer in the housing. It will probably make the knotmeter not work but I am more concerned about depth.

As for deadrise, the boat originally had the depth finder mounted on a shaped wooden block so it pointed straight down. And that's how I mounted the new one. If I mounted it flush with the hull it would probably point off to the side and miss the wing but the depth would have been off by some sine or cosine but would have been better than what I have now.

 

[Ralph Johnstone]

If you're willing to skip the knotmeter, you may be able to mount the assembly as an interior mounted, shoot through the hull transducer. If you are not familiar with this method, see:

drilling holes thru the hull ...

I am about to drill a 2" hole to install a depth/speed transducer, and wondering what I might find. is it solid or cored beneath the v-berth? thanks ...

forums.sailboatowners.com

See post #9

 

[Ward H]

Jim,
Are you sure the DST800 is compatible with your display instrument?
What display are you using for depth?
Have you tried calibrating the depth sounder?

Be careful trying to install the transducer turned in the thru hull tube. The ones I’ve seen have a notch so they can only be fully inserted in the proper direction. If you try turning it it may not fully seat in the tube causing a leak.

Maybe try reinstalling the old depth finder transducer to ensure the display is still working properly.

 

[jim.m]

The display is a Raymarine p70s which was part of the autopilot kit I installed. It is definitely compatible. Knotmeter and temperature sensor work fine. Unfortunately, I tossed the old depth finder and display. I will check for that notch you mentioned.

 

[Ward H]

Yep, compatible. I bring my speed and depth into my P70s display.
Is your DST800 connected directly to your Seatalkng network (“smart transducer) or through an iTc5?(“dumb transducer“)

Both need or can be calibrated / offsets entered. IE: With offsets you can set the depth readout for water depth or depth under keel.

Not all displays can calibrate/adjust offsets.
I have an i70s which does. Not sure if the P70s can.
Have you tried that?

 

[Ward H]

As for deadrise, the boat originally had the depth finder mounted on a shaped wooden block so it pointed straight down. And that's how I mounted the new one.

Considering that you mounted the new one same as the old one and the old one worked, I don’t see how the wing is in the way with the new one. Yes, the depth portion of the transducer is half of what the old one was but I don’t think it cuts the beam in half vertically.

With that said, I agree with trying to turn the transducer 1/2 way around to see if that fixed the issue, even if you can’t fully seat it in the tube.

If it doesn’t, find out from your supplier or Google how to set offsets for depth for your transducer. I did a quick search in the P70s manual and did not find any instructions on doing so. Only how to set data sources.

PS where in the boat hull is the transducer mounted? Under the v-berth ?
behind the galley? How far from the centerline of the hull?
That may help in determining if it is over the wing keel.

 

[Joe]

I'm wondering what advice the manufacturer might have to offer.