Fishmark 480 frustrations! Looking for some advice....

[MNBIGBEAR]

I have a Eagle Fishmark 480 mounted on an Alumscraft Trophy 175. I currently have it mounted about half way between the outside of the transom and the center line of the hull. It appears to be approximately half way below the bottom of the hull as the directions state to mount it.

The problem: I constantly lose the signal anytime I start to move indicated by the depth reading blinking at me. There seems to be no rhyme or reason to it other than at high speed I lose the signal every sinlge time. I also get alot of "noise" on the screen when I am moving which makes it nearly impossible to see baitfish schools and fish.

I have messed with the sensitivity a little and some of the other settings but to no avail. I am sure this subject has been covered in other posts on here in the past but wasnt having much luck searching this specific topic. ANY suggestions woud be greatly appreciated. Change of wiring? Moving the transducer? Different settings? Hope you guys can help. Thank you in advance for any advice.

[JohnMickish]

Check to see that is it not behind a line of rivits. Rivits cause turbulance and then your tranducer loses contact with the bottom, and then it will flash (that's the signal to you that it is NOT activly ready the bottom) the last reading it had.

[MegaHawk]

move the ducer. I have my ducer mounting plat about half an inch up from the bottom of the transom and halfway in between the motor and gunnel.it scoops water so i put a piece of plastic over it like a hood to keep teh rooster down.works like a charm!

it sounds like when ur boat moves it creates a air bubble by the ducer. thats a possibility y ur reading goes out.

[MNBIGBEAR]

Thanks for the tip. Didnt think about the rivet lines causing a problem. The transducer bracket is mounted right to the boat. Would it be beneficial to use a mounting plate instead since I have to move it anyway?

[jentz]

Well the mounting plates are for not drilling holes below the water line,If you use some closed end blind rivets on the existing holes then a mount plate,With out those rivets its possible you may have to remove the mount plate to reseal holes.Unless the plate dont cover them.

I just passed on a nice Lund cause there were 8 different holes where ducers were mounted.WAY to many if it were just 2 I can accept that.People dont think what the consequences of all those holes can produce down the line

[MNBIGBEAR]

Thats exactly what I want to avoid. Looks like I might have my weekend project!

[Ed Carlson]

Mounting plates are cheap $14, and as you already was warned, no need to make a sieve out of the transom to find a good location for your various sensors and ducers.

You can remove and plug old mounts with silicone and then epoxy the new plates to the transom using Marine grade epoxy. The epoxy will double seal the old holes and leakage should be a non-issue. A good epoxy job will not require any screws to keep the plate firmly attached.

When your at it, just as well add a second plate on the opposing side of the transom, then you have redundant mounting opportunity's if you ever need to add another unit. No real extra work when your mixing the epoxy now, and it will save you a lost weekend down the road.

Also take your rollers or bunk boards into consideration for placement, so you do not bump and misaligned ducers or damage sensors while loading and transporting. If the rollers/bunks remain a complication, then slide back your boat on the trailer and adjust the wench position back a few inches. This will also lighten up the hitch weight a bit. A few inches for safety's sake will not influence towing much, may help in fact.

[Surface Tension]

How much ducer would you say is below the transom? If you go too far you'll create cavitation.

Using a straight edge on the hull, at the highest point of the dead rise I'd have the bottom of the ducer no more then 1/4". If you have steep dead rise I might lift the ducer more to flush with the bottom of the hull. The inside edge(toward center point) of the ducer will be below the hull.

Before you do that check the angle of the ducer. Is it on an even plain with the hull?

The type mount you have has a tendency to rock back lifting the rear of the ducer. That is not good and will create cavitation as well. I always tip the rear of the ducer down a hair from even with the hull. That will ensure the face of the ducer makes contact with the water at high speeds.

The mounting board is good advice. The boat will be around for a long time but it might have upgrades to electronics many times over. Plus if you have to mover locations a bit or make adjustments your not drilling more holes in the boat.