Finally got a clear picture at speed - FCV620

[marto78]

I have owned this unit for 3 years now and because of the shape of my hull it has been driving me crazy as I have not been able to get a clear picture at speeds over 20km/hr even on a calm day. After drilling countless holes and trying different store bought brackets all over the back of the boat I decided to design a bracket and take it down to the local engineer to weld up for me.

He did go a bit over board in the strength side of things. But after the results of the weekend where I was able to sit on 30km/hr in a 10-15kt northerly and spot a school of fish hanging off the back of a bombie in 65m of water I am very happy with the way it turned out.

I was even able to sit on 45km/hr on the way home and still get a perfect picture.

pic 1 is of the bracket up and out of the way.
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pic 2 is dropped down in the clean water when cruising along
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[Seahorse]

Mate what a good lookin bracket.
Glad it all works now

[nautimax]

Looks good! What is the make and model of your tranny?

[marto78]

Looks good! What is the make and model of your tranny?

Airmar P66

[Malcolm W]

Looks like you had to go deeper than most to get to clean water.

I've had a couple of p66s, one on a pressed bottom boat like yours and it took a lot of adjusting as well.

Bought my latest sliding bracket from BCF, not as good as yours though. Using it to slide up and down for beach launching.

[whiteman]

I couldn't get mine working with a Quintrex. Sold it and went to Garmin which is an inferior sounder but it does hold the bottom. Yours looks very deep (got a side on photo?). What's the rooster tail like? When I had mine in the deepest setting I snapped the plastic lock twice. I would go back to Furuno in a heartbeat if I could get a clear picture on the plane in a bit of chop. I used to lose depth over 10 knots and picture a lot earlier.

[marto78]

I found the deeper I run it the less rooster tail there was and I had a triangular piece welded onto the front of the bracket to make it a bit more slim line. It is also angled forward slightly for a bit less drag again.
I did have a faulty quick release on my first tranny but that one is no longer after the transducer disappeared somewhere between the c
cape and Bulwer.
When the rain stops I will get a few more pics up for you if you like.

[ZigZag]

Hi Marto,
I have a similar problem with my Haynes Signature 500 RF .. How far below your boat bottom do you have to go in order to get the best return ?

[nigelr]

Great post marto, I reckon this may be a problem with a lot of boats and various different transducers; my old savage has a pressed ali hull and the h'bird tranny is pretty rough at planing speed. I have gotten used to it though, and have built a sliding bracket but nowhere near as professional a job as yours! Think I'll give running the tranny a bit deeper a go.
Cheers.

[Horse]

I tried a lot of things before drilling a big hole and fitting a bronze through hull tranny. It certainly works well but its a step most are reluctant to make

[marto78]

A couple more side on pics:

Looking from under the motor with the bracket down.
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And looking from the other side with the bracket up
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[marto78]

Hi Marto,
I have a similar problem with my Haynes Signature 500 RF .. How far below your boat bottom do you have to go in order to get the best return ?

I think the destruction book says about 5mm below with a slight angle (or something or other I gave up on that thing years ago), but with mine because its only a tinny and bounces around a lot I found that I had to at least have the top of the transducer under water but to get less back spray I had to have the top of the mounting bracket under a fair way as well. I'm not real sure on exact measurements as it all sits below the water line and I just push it down until the pic is good and there is no more rooster tail, then lock it in place for the weekend.

[ZigZag]

Hi Marto...Thanks for the info. Really something to think about.

[Dignity]

Marto, great looking unit. I am not sure if there is something I missed but it appears you are relying on a wing nut to keep the unit from dropping down and putting stress on the cable. I would tap another hole at the maximum depth you would want to slide the inner tube down and put a bolt in there so that if the wing nut comes loose it can't drop any further than the bolt head if you get my drfit.

[whiteman]

That is soooo deep! And explains why I had no chance with it attached to the normal transducer mount. Your local engineer should make a few of those things and post them on this site. If I still had my 620 I would have bought one (and added Dignity's suggested mod).

[Dignity]

Marto, had another thought, I would put a vertical groove in the inner tube so that the wing nut bolt would lock into this groove (would prefer 2 wing nutted bolts) this way if the inner tube slipped/loosened then the transducer wouldn't spin around and cause damage to the cable. This would depend on the gauge of the inner tube and whether it was viable, if there is no thickness there then I would definitley go for an extra wing nut. I may be a security nut but as I can't afford one of those transducers at the moment I would look at protecting it as much as possible. I do like the protection you gave to the front with the angled bracket.

[marto78]

The angled bracket at the front wasn't so much for protection but to reduce drag in the water, a home made bracket I tested earlier had that much drag that it was acting like a trim tab and lifting the stern of the boat up on that side.
I found the best way to get it straight was to be doing about six knots when lowering it and it sort of alligns itself.

When I get some time I may look at making up a pin or something to lock it in the down position so that it has no chance of moving anywhere.

Thanks for the ideas Dignity I will definetly be putting in that bolt at the top to stop it falling out.

Marto