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Author Topic:   AIRMAR P58 Transducer Placement
edgarop posted 09-15-2013 12:48 PM ET (US)   Profile for edgarop   Send Email to edgarop  
Hello all. I have had a [Raymarine A57d] for a couple years. I have yet to be able to adjust the Airmar P58 transducer correctly. It reads bottom decently at a slow salmon troll but loses bottom when going 5-knots. Bait doesn't show up in balls but in vertical streaks. I have a counter-rotating single HPDI. The transducer is mounted on the starboard side [of the transom of a Boston Whaler 22-foot hull]. I've tried anywhere from flush to bottom and down 3/4-inch below hull. I don't have shims installed. What do you guys think?
silentpardner posted 09-15-2013 04:10 PM ET (US)     Profile for silentpardner  Send Email to silentpardner     
I would move the transducer further away from the propwash. The heavily aerated in the direct vicinity of the prop could be making the transducer read through air bubbles where it is.
jimh posted 09-16-2013 12:01 AM ET (US)     Profile for jimh  Send Email to jimh     
How far off centerline is the transom-mount transducer mounted now?

Did you follow the Airmar instructions regarding distance from keel centerline? I do not recommend you move the transducer any farther away from the keel centerline than the distance recommended by Airmar, which should be about 12-inches. Moving the transducer outboard farther is going to make it tend to have more problems performing when the boat is on plane. This is because the hull tends to lift out of the water. If the the transducer is mounted too far outboard from keel center line it will become raised out of the water when the boat is on plane.

There is nothing particularly unusual about the transom of a Boston Whaler 22-foot hull in regard to SONAR transducer mounting. If a SONAR transducer works at rest but not underway, the usual problem is disturbed water coming off the hull. Make sure you have not mounted the transducer in-line with some hull strakes.

By the way, with a counter-rotating propeller, you should have the transducer on PORT side if following the AIRMAR recommendations. They like the propeller blade direction to be going downward on the side you mount the transducer. But I don't think that is the problem.

edgarop posted 09-19-2013 01:47 AM ET (US)     Profile for edgarop  Send Email to edgarop     
Thank you jim its about 15 inches from center line. It is mounted partially behind a strake that is about 8 ft forward. Im.gonna try mounting it closer to keel not inline of a strake.
jimh posted 09-19-2013 12:09 PM ET (US)     Profile for jimh  Send Email to jimh     
In the AIRMAR installation instructions they offer some excellent advice on assessing the transducer immersion. Let me try to summarize it:

Assuming the transducer is mounted on the Starboard side of the transom, if the transducer loses signal when the boat lists to Port, then the transducer needs to be immersed more deeply.

I am still in the process of finding the optimum location for my new SONAR transducer. I have it mounted too far off keel centerline. (I have two transducers on the transom, and the existing one is mounted closer to centerline. I mounted the new transducer farther off centerline, and also with a notion of perhaps covering up some existing old holes from another device--speedometer Pitot tube pick-up--that had been mounted on the transom. But that location has proved to be troublesome.) If the boat has any list or lean to Port, the transducer loses the bottom. I am going to move it more inboard (but not until next boating season--it is too late now for fiddling with this problem).

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