Through-Hull Transducer Questions

[smallie.huntin]

I just purchased a Hummingbird 587ci Fishfinder and GPS.  I'd like to mount the transducer in the hull (to avoid drilling anything into my fiberglass hull).  The owners manual is telling me before I mount the 'ducer with epoxy that I should flood the bottom of my boat with enough water to cover it then weigh it down in the spot I am thinking of mounting it.  This should give me a good idea of the best spot in the hull to mount the 'ducer. 

There is really only 2 spots that I can find a clear area in the bottom of my boat to mount the ducer. 

Has anyone flooded there boat to test out mounting spots?  Is there a better way to go about this?  Should I really consider mounting on the outside of the hull to get better picture or is it not worth it?

If flooding the hull is really the best way..how do you go about that? 

Thanks for the help!

[Wayne P.]

You won't know exactly were in the hull to get the best performance without doing that procedure. That is why it is recommended. All you need is enough water in the bilge to cover most of the transducer ( a couple of gallons may be enough). You need to put weight on the transducer so it will vibrate the hull at the same frequency as the tranducer transmit/receive.

Lots of boats, especially fiberglass bass boats, have a thin smooth area in the hull near the drain plug that is prepared for that purpose.

Shoot thru mounting does result in some sensitivity loss as compared to a transom mount, but a quality unit will perform very well with a properly installed transducer. The flat faced trolling motor type transducer is easier to install correctly rather than the torpedo shaped transom type although either will do well IF properly placed and installed.

Mounting one on the transom is problematic for consistant high speed performance and it is subject to damage. Mounting a shoot-thru will have the transducer in the least disturbed flow of water you may ever get.

[Al Wolbach]

I have used epoxy to mount several transducers without ever flooding the hull. Make sure to locate a flat level area on the hull bottom as near the transom as possible. This will allow the unit to work while running on the pad. After selecting a location lightly sand the hull and transducer with about 60 grit paper to allow the epoxy to adhere. Wipe down the sanded area with rag wet with acetone to remove any oily substances and allow to dry. Mix the epoxy( I use a popsicle stick) and spread it over the transducer bottom. Push the transducer to the hull with a twist to remove any air bubbles. Place a weight on the transducer to hold in place for 24 hours and you are done.

I would say the two most important steps are selecting the location and making sure there is no air in the epoxy. On the location make sure it is the very bottom of the boat and the other side of the hull is as smooth as possible(no chines). Mix the epoxy trying to be as smooth as possible, but mix entirely while trying not to allow any bubbles. And be sure to twist the transducer, as it comes in contact with the hull, during installation and push down hard.

This sounds a like it may be hard to do but it is very easy. Location, location, location.

If you are not sure you want to tackle this a dealer will install it fairly cheap. Let them do the epoxy work and you do the rest.............Al

[Al Wolbach]

One possible problem not mentioned is a built in temp probe. If your transducer has a built in temp sensor and you mount it to shoot through the hull it will read the bilge temp not the water temp.

On one unit I installed I had to order a different transducer from Lowrance with an external temp probe in order to read the actual water temp.

Wayne is right. The puck type are easier than the torpedo type to install....................Al

[Wayne P.]

Another note, only use the slow cure epoxy and mix it slowly to prevent bubbles. The 5-minute type gets lots of bubbles in it when mixing

[smallie.huntin]

Thanks for the responses!  I will be doing the on-the-water test Friday...can't wait to get the boat out.