problems with fishfinder, need halp, thanks!

[xpertski]

hello all, last year used the fishfinder for first time, its a hummingbird high res one, it seems fine when stationary, however when moving at anything over a few knots, the screen goes all grainy, and fuzzy, and yet the spec says it can handle high speeds up to 70mph, so should be fine..........what is the problem? could it be that turbulance from prop is interfrering? if so what should i do, if i move it much further away from prop, it would be very close to waterline, or should i mount in well at back of boat?

[roycruse]

Transducers are very susceptible to turbulence in the water - some pictures of where you have mounted the transducer may help diagnose the problem.

In my opinion the transducers are always better off glued into the hull in the drain sump at the back of your boat (ie where the hull is thinnest or single skinned)

My Garmin transducer is glued into the sump at the back and will track the bottom at 25 knots in 65m deep water which i was most impressed with.

[xpertski]

hmmmmmm, could try that, so your suggesting gluing it in the well inside the boat? then i guess just put some sealant in the drill holes on the transom where it used to be. id love to post some pictures, but unfortunately my rib is an hours drive away in a compound so not too easy. i just thought id start to think about how to rectify problems before the season really kicks off!!! haha! its so annoying when you have a good read out from fishfinder, then after a certain speed it goes crazy saying its 1000ft deep etc, and blurred screen. unless its just a massive shoal of fish always following me around under the boat! haha!

[codprawn]

If you put it inside the boat you need a "through hull" type - different transducer to the type that fits to the transom.

"Through hull" are better at speed but not as accurate or deep reading as transom mount at lower speeds.

Repositioning will help a lot - bit of trial and error involved though.

[roycruse]

Codprawn - I have always given you the benefit of the doubt when you've been in conflict with someone else - Ive even agreed with you on many occasions - but this time I'm afraid you are talking complete bollox !!!

And for the first time I can see why you infuriate so many people - you have posted in here what appears to be a very authoritative statement as if you know a lot about fish finders yet what you say is completely inaccurate.

1. "If you put it inside the boat you need a "through hull" type" - No you do not need a through hull transducer to mount it inside the boat - I have had 2 boats with a standard transom mount transducer epoxied into the inside of the hull.

2. ""Through hull" are better at speed but not as accurate or deep reading" - perhaps you missed the point where I said my sounder was tracking the bottom in a depth of 65m - how deep do you want to go?

3. "bit of trial and error involved though" - are you recommending drilling holes all over the transom until you find the optimal place for it.

[roycruse]

heres an excert from a transducer manual - it expalins how you can test the transducer for use inside the boat without having to do anything permanent.

To avoid drilling a hole to mount a thru-hull transducer, a transom mount transducer may be used with epoxy inside a boat (“shoot-thru-hull” installation). For a transducer to be mounted inside the hull (shoot-thru, not thru-hull), the boat must be fiberglass, no core (contact your boat manufacturer if you are unsure). Test by placing a small amount of water inside the hull, placing the transducer on top of the water, then verifying the accuracy of the locators versus the current water depth. If they are the same, use slow-curing epoxy (non-silicone based) to affix the transducer to the inside of the hull.

[xpertski]

thanks for the advice guys, i was wondering how trial and error worked with drilling holes for transducer i assume that by fixing the transducer with epoxy in well, if it were to be removed, the epoxy is also removable. the boat is a humber ocean pro 6.3m, its last years boat, i think they use a marine ply core for the transom, but not sure about the hull, i think its all grp....unless someone knows, ill check up on that!
so by placing in well would it give me reading from say inside well to floor to check accuracy?
thanks again for the advice!!!!!

[Polwart]

Originally Posted by xpertski

i assume that by fixing the transducer with epoxy in well, if it were to be removed, the epoxy is also removable.

Epoxy is virtually impossible to remove other than mechanically - e.g. by sanding, drilling, grinding, cutting etc. So I wouldn't epoxy it in until you are sure you have the right spot for it.

[roycruse]

The idea is that as long as you have nothing but glass fibre hull between the transducer and the water that hull will transmit the sonic pulses pretty much as well as the water does.

So allow some water to collect in the well and simply place the transducer in the pool of water touching the hull and the sound waves will travel through the water and hull into the water below. If you get good readings then simply glue it to the hull with epoxy (try to get as few air bubbles in the glue as possible when mixing it - and avoid trapping air when you place the transducer onto the glue) - if you ever need to replace it as Polwart says it can only be removed mechanically - I usually find carefully chipping it away with an old wood chisel or screw driver and a small hammer works best

[Pete7]

Sorry codders, I am with Roy on this one, they will work perfectly well. The only other thing I would add is that we used a silicone sealant to glue the tranducer in. Yes I know it says not to in the manual but we did anyway as a temporary measure for one afternoons diving. That was in 1997 and its still in place and working in the club diving boat. It means we can easily get it out again if we need to or if the signal wasn't vry good it could be moved again.

You must get to the inside of the hull though, some ribs have a flat ply plate glassed into the transom with a space underneath, if so the transducer won't work if its glued on top of this.

Pete