Demonick's Kayak Fishing Pages: Hobie Mirage Revolution Transducer in Foam Installation

For the general features, advantages, and disadvantages of the Hobie Mirage Revolution see the general features page.

Transducer

As described on the Hobie Mirage Revolution general features page the mirage drive drops through the boat and the flippers extend into the water. When mounting a transducer it is important to place the transducer such that the when extended the mirage drive flippers do not impinge on the transducer sound cone.

A typical transducer sound cone is 60 degrees. The turbo flippers extend 16" below the hull. With basic trigonometry we can calculate that the transducer must be at least 9.25" from the edge of the flippers. If the transducer is mounted just forward or just aft of the mirage drive hull cut out, when the flippers are extended they will be in the transducer cone. To clear the flippers I chose to mount the transducer just aft of the crotch hatch. This places the transducer under the seat, near the center of the boat.

The basic design of this type of transducer mount is a closed-cell foam "doughnut" roughly the shape of the transducer. This "doughnut" is glued to the inside bottom of the hull with a generous, contiguous bead of Marine Goop. The foam doughnut is then filled with fresh or salt water and the transducer press-fit into the center of the foam doughnut until contact is made with the hull. This creates a continuous acoustic connection from the transducer to the water outside the hull.

The water surrounding the transducer will need to be replaced at the start of each trip, and perhaps more often depending on boat handling, tightness of press-fit, sea conditions, and evaporation. Because of this, various substances are occasionally used as a substitute for water, including petroleum jelly and grease. This installation will employ grease.

For the installation you will require:

• A transducer - generally a transom mount model
• A block of closed-cell foam - a large diameter pool noodle works well
• A very sharp, thin knife, like a boning knife
• Marine Goop
• Water or grease or petroleum jelly

1. Note that the block of closed cell foam is thicker than the transducer.
   

   
   

2. Marine Goop, the type of grease, and a knife. The grease is a water-resistant, high-temp calcium sulfonate complex and recommended for corrosive marine applications.
   

   
   

3. Cut foam installed on hull. A nice oozed bead of Marine Goop can be seen around the foam.
   

   
   

4. Transducer grease mounted with cable neatly coiled. The final step was to put about an 1/8" layer of grease in the foam cup and press fit the transducer into the foam until it contacted the hull. I may cut a foam plug to fit into and over the foam cup to keep the transducer secure through boat handling. DO NOT USE TOO MUCH GREASE. Unlike water the grease is very viscous and nearly impossible to squish out the excess without blowing out the seal on the foam reservoir. Also floating the transducer on a layer of grease above the hull will GREATLY affect transducer performance. I had to remount the transducer 3 times, with less and less grease each time.
   

   
   
   

   
   

5. Performance: For over a year the grease and foam mount worked well. While the original foam and water provided a good bottom return down to about 800 FOW, the foam and grease mount provided a good bottom return down to about 500 FOW.

   However, after about a year the preformance became flakey, providing a good bottom return with bouts of virutally no bottom return. Remounting with new grease provided performance for a while then succumbed to same problem.

   Remounted with Duct Seal. See: Transducer in putty