posted 07-22-2013 01:57 PM ET (US)        

The P66 is significantly larger than the Lowrance Skimmer 83/200-kHz transducer that was supplied with my Lowrance HDS-8. This is a large hunk of molded plastic! The area of the transducer active element surface that is in the water is many times larger than the Skimmer.

The AIRMAR mount is a complicated assembly of molded plastic with several retaining levers or arms that once locked in place depend on the flexibility of the plastic to be released. The transducer snaps into the plastic mounting bracket, a cover swings up to retain the pivot point, the transducer can then lower into operating position, where another plastic lock retains it in position. A strike with an underwater object should create enough force to bend the plastic of the position lock, allowing the transducer to swing up, while still being retained by the pivot lock.

The cable is integral with the transducer and is sealed in place. The cable is made with a nice insulating jacket. The feel and flexibility of this cable is better than the cable used by Lowrance in their Skimmer. The supplied cable is quite long, much longer than the Lowrance Skimmer. The longer cable was a nice benefit. On my boat, I had to extend the Skimmer with a $40 extension cable. The P66 cable was long enough to reach my helm position and have about ten feet left over. Clearly AIRMAR intends that this device may be used on larger boats.

I selected a mounting location on my transom on the Starboard side. The Skimmer is already mounted there about 13-inches from keel center line. I put the P66 about 5.5-inches farther outboard. AIRMAR provides a hole template with marks indicating where to align to the transom. Three holes are needed. The mounting holes are in a horizontal line of three. The plastic bracket has three vertical slots. There is about 0.4-inch of adjustment room in the slots.

My initial positioning of the mounting bracket was to orient the bracket almost to the bottom of the slots, that is, to begin with almost the highest possible mounting location for the transducer. This proved to be (what I hope will be only slightly) too high.

AIRMAR gives a valuable method to determine if the transducer is too high or too low. They suggest watching the echoes while making a turn to the left and right. If the transducer is mounted on Starboard, and you turn to the right, the Starboard side of the transom will lower into the water. If the SONAR echoes improve in a right turn, the transducer is mounted too high and should be lowered. If echoes improve in a left turn, the transducer is too low and should be raised. Using this method, I saw the echoes improve in right turns.

I have lowered the transducer to near the top of the slots, that is, made it run deeper. I have not re-tested since this change.

The first few days of testing were a bit disappointing. The sea was exceptionally calm. I think this resulted in the boat running on plane with very low bow rise, making the immersion of the transducer less than normal. The P66 was not getting good results when on plane. However, later in the week, we had to run into some typical head seas, with the bow running higher than in calm water. This helped get more transducer into the water, and the results on plane were better.

The temperature sensor seems accurate. I did not make any tests of it other than to go swimming when it said the water temperature was 76-degrees.

The paddlewheel sensor tended to show speed through the water that was lower than the speed over ground deduced by the chart plotter using its GPS receiver. I applied a correction factor of 120-percent; that is the maximum compensation available. My impression is the paddlewheel might need more immersion, too. It may have been operating in foamy, airy water.

posted 07-22-2013 10:31 PM ET (US)            

The HDS 7 internal antenna has exceeded the performance tracking of my previous Lowrance unit that was equipped with an external antenna.

I keep my Whaler in a metal boat shed here in Jacksonville, Florida, and the new HDS 7 internal antenna actually tracks and locks in GPS satellites while inside the shed. It takes longer to lock in three satellites than outside the shed, but it eventually gets there.

While offshore trolling in various areas in Florida, I frequently see depths ranging from 100 feet to 1200 feet. So far, the P66 unit has provided consistent readings/markings in all depth ranges.

I normally use the 200 kz mode until I reach depths exceeding 500 feet. I then switch to the 50 kz mode.

The only minor issue that I have experienced, is that when running in very rough water, the transducer's mounting bracket pop up mechanism will activate if the face of the transducer lands just right creating the right amount of upward pressure. It is a simple fix to push the transducer down to lock it back in place. A tell tale sign has been an immediate loss of bottom readings.