Transducer mounted wrong?

[bashr52]

While I have my boat home for some spring maintanence, I'd like to figure out what is going on with my fish finder. It seems in deeper water it is reading ok, but if I get into anything too shallow (under 6-7 feet) the unit just defaults to reading 4.3 feet. It is a 3 year old Humminbird 500 series with a transum mounted transducer. Could it be the angle is set wrong? Also, if moving above 5-10 mph, it sometimes reads ok, sometimes doesnt (defaults to 4.3). It paints fish while moving, but if I stop in an area where its been painting fish, the screen goes empty. Occationally I will get it to paint someting while sitting still, but more often than not I do not get anything.....

Sorry for the vauge explination, but I have not had the boat out yet this year and am relying on what I remember from last season

 

[Silvertip]

Re: Transducer mounted wrong?

First -- fish finders cannot find fish. They are "locators" (big difference). The transducer cannot be mounted in line with any obstructions on the bottom of the boat. Obstructions such as lines of rivets, strakes, etc creates bubbles and transducers cannot read through them. I wold not be concerned about not reading in four feet of water. You should be able to see the bottom at that depth unless you are in really foul water. Lastly, about 90% of what is painted as fish on the screen at any speed are not fish. Turn off the fish symbols and use the sonar arches to identify fish.

 

[bashr52]

Re: Transducer mounted wrong?

First -- fish finders cannot find fish. They are "locators" (big difference). The transducer cannot be mounted in line with any obstructions on the bottom of the boat. Obstructions such as lines of rivets, strakes, etc creates bubbles and transducers cannot read through them. I wold not be concerned about not reading in four feet of water. You should be able to see the bottom at that depth unless you are in really foul water. Lastly, about 90% of what is painted as fish on the screen at any speed are not fish. Turn off the fish symbols and use the sonar arches to identify fish.

I should have been more clear I guess It is not that the thing will not read in 4 feet of water, it is the fact that below 6-10 feet, it just flat lines and spits out 4.3 ft. That is where I need it to work the most as I want to see trends to avoid running aground in shallower water. This is a fiberglass boat, so no rivets or anything to cause bubbles, it is smooth. There is still a waterline on the boat from last year, I think I will try resetting the transducter to be parallel with this line, rather than the bottom of the boat. Does this sound like a correct way to set it up?

 

[JoLin]

Re: Transducer mounted wrong?

No, don't raise the transducer on the hull. It should be mounted at the bottom. Most (many?) have a provision for you to add + or - offset to the finder reading, depending on whether you want it to display actual depth of the water, or depth under the keel.

I can't explain the 'default' reading of 4.3 feet. Sorry. Did this just start happening?

 

[nphilbro]

Re: Transducer mounted wrong?

This is crazy! Mine just started doing basically the same thing but flatlines at 1.2ft but will be intermittently clear and fine. Last Saturday we were on the Puget Sound and it clearly pinged 420ft for about a minute or two. I was having the same issues on a freshwater lake a few days earlier two. The only constant in the myriad of variables is that it never worked when I took the motor up to speed. My boat is fiberglass as well.

I have a 15hp 2-stroke evinrude pull-start kicker on port side (pull-start, independent of everything else on the boat except the fiberglassed transom plate), a 140 2-stroke Johnson in the center and the transducer 25" off center to starboard. The fishfinder is wired to a shared ground but I finally hardwired it back to the main power terminal in the stern to see if there was any change. NADA! Motors off/on, accessories off/on, boat moving (at 5mph or less)/boat still, radio off/on, cell phone on/off - there is just nothing consistent here. It will even start and stop reading while turned on and I've tried resetting many times but it seems to only work when it wants to. I've even jiggled the transducer wire from helm to stern with no change in operation.

I say this is weird because my next door neighbor came over this morning to borrow a prop (yep - that kind of neighborhood) and saw my fishfinder on the dash and commented he has the exact same one - but it quit working and flatlined at 10.2 ft with intermittent operation last week when he was on the columbia!. He has a 18ft weldcraft aluminum but his fishfinder has worked great for a long time.

I'm wondering if there is a software timeout or something. This could all just be coincidence but seems "fishy" to me. I'm on my way to Auburn Marine in a few minutes and will see if they can tell me anything.

 

[Star]

Re: Transducer mounted wrong?

Finders are a study onto themselves. You never mention what brand or model. Is it a duel beam, or dual frequency? Transducer placement and angle are important. You can read all about the advantages of each system but in the end you just have to make it fit your type of fishing. Yes you may have problems with your unit, but my guess that it is not setup right. I have an old garmin GPS Map 398 and for the first two seasons I changed two differen't transducer and had settings all over the lot. I felt that I had made a big mistake not getting a Lorance, but I really liked all thee US lakes
on the GPS side with ramp locations. After many different setting.. fishing mostly fresh water lakes I have it working well. Now when I see fish on the screen there are usually fish there, except in shallow water it reads rocks as fish alot.
Here is the end of the story, I troll alot and I have found that if you get a strike or a fish mark a waypoint and direction of the troll and 8 times out of ten you will get fish there. Whatever structure, weeds or drop off is there fish will hang out there!!! Use the power of all the great electroncs to improve your success and safety.

 

[dingbat]

Re: Transducer mounted wrong?

It sounds like your saturating the signal or have a dog slow ping rate. Either way, take the unit out of auto mode and manually turn the gain down as low as it will go. This should take the unit out of saturation and allow you to see the bottom. Slowly turn up the gain until you get a solid bottom. Not position and turn up the gain until you saturate the screen again. The right setting is somewhere between position 1 and your saturation point.

If this doesn’t work, you have a transducer problem or the unit’s ping rate is to slow to operate that shallow.

 

[nphilbro]

Re: Transducer mounted wrong?

Problem Solved!

My fishfinder is a Humminbird 550. I didn't take into account that when I recently hooked up the new 50 gallon mid-back hull fuel tank and removed the 6 gallon temporary tank from under the splashwell the weight-forward shift changed the characteristics of the hull displacement enough that what worked had was now too turbulent for it to read while moving. I'm surprised that I even had intermittent reads while motor was shut off after I changed tanks.

Completely frustrated upon returning from the bay Saturday, I reread the transducer installation instructions and when I looked at the transom I could clearly see from the waterline the stern was riding a good 3-4" higher than before and the transducer would have likely only been underwater while I was hanging off the back to see if it was underwater!

I remounted it 5" closer to center (21 degree deadrise) and again so the transducer has the 3-5 degree angle below the stern for forward view. I took the boat out to last night with my son and Viola! We had great readings everywhere - from the shallowest depth of 5ft at launch to 400+ft crossing the bay. It's rated up to 25mph but there were breakers in the open water so I didn't go over 10-14 knots but we had clear depth readings the entire way with blips indicating it was picking up something in the middle.

Right now we're chasing lingcod so we cover too much different terrain type to worry about how accurately it sees fish- we start out catching dabs for bait in 30-50ft of sandy slope (any deeper and they die in the well) to presenting our new bait along shelves that can drop 100's of feet down for toothy critters hiding in ambush holes. Anyway, I'm only worried about reading depth for structure and shelves but I'm looking forward to seeing how well it works the next time I launch in a lake to see how well I can dial it in.

 

[bashr52]

Re: Transducer mounted wrong?

I may be in a similar situation (Mines the 525). I noticed Monday when I had the boat out that I'm getting a decent amount of spray off the transducer when traveling. Looks like I need to relocate!