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  HDS-7 with AIRMAR P66

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Author Topic:   HDS-7 with AIRMAR P66
floater88 posted 08-16-2011 09:15 PM ET (US)   Profile for floater88   Send Email to floater88  
I have a REVENGE 20 W-T. I have installed a Lowrance HDS-7, and I can't keep the depth locked in at planing speeds. I've mounted the transducer according to the manual and adjusted it up and down, and still no luck. Has anyone used the Airmar P66 transducer? How has it worked out? Thanks
jimh posted 08-16-2011 09:44 PM ET (US)     Profile for jimh  Send Email to jimh     
With my HDS SONAR, I have had good results with the GAIN in the AUTO mode. I can maintain bottom echoes at planing speeds up to over 700-feet of depth. The immersion depth of the transducer is critical. A change as little as a 1/4-inch can make a difference. I am not using a P66, but rather the stock Lowrance SKIMMER 83-200-KHz transducer. The P66 looks like a larger device. It may be more sensitive to water disturbances from water flow across it.
Fishmore posted 08-17-2011 01:46 AM ET (US)     Profile for Fishmore  Send Email to Fishmore     
I have a Montauk with a P66 transducer. It reads bottom right up to full throttle.

It sounds like you either need to increase the ping speed of your depth finder or you need to move the transducer to a better location on your transom. You might also ensure that the bottom of the transducer is level by ensuring the boat is level and then placing a level on the transducer and then adjust it accordingly.

jimh posted 08-17-2011 08:09 AM ET (US)     Profile for jimh  Send Email to jimh     
In another article on this topic (now deleted), it was mentioned that the location of the AIRMAR P66 on the transom was "near the [first bottom strake] away from the motor on the starboard side." In general you do not want to mount a SONAR transducer directly downstream of a strake on the hull bottom. When the hull is running on plane, water coming off the hull in the area of the strake will be disturbed and aerated. Such water will interfere with SONAR operation.
floater88 posted 08-17-2011 08:12 AM ET (US)     Profile for floater88  Send Email to floater88     
I took some pics of the transducers location so you guys can suggest a better location.

http://i123.photobucket.com/albums/o316/sterios/DSCN0470.jpg

http://i123.photobucket.com/albums/o316/sterios/DSCN0469.jpg

http://i123.photobucket.com/albums/o316/sterios/DSCN0471.jpg

I adjusted it down a little and i'm going out now to give it another test. Thanks

Fishmore posted 08-17-2011 09:00 AM ET (US)     Profile for Fishmore  Send Email to Fishmore     
Floater, that is not an Airmar P66 transducer it is a LEI (Lowrance) Skimmer transducer. That is the same one Jim has.

As far as placement and alignment I will defer to Jim so he can supply his mounting location as he seems to get excellent performance with the same set up that you have.

floater88 posted 08-17-2011 05:51 PM ET (US)     Profile for floater88  Send Email to floater88     
Yes I know it's not an Airmar P66 as i'm looking at getting one to replace the original Lowrance unit. I took the boat out today and fiddled with the transducer. It works great when i'm turning to either port or starboard on plane but when I straighten out I lose the bottom. What could cause this?
jimh posted 08-17-2011 08:06 PM ET (US)     Profile for jimh  Send Email to jimh     
The initial question was not particularly clear. There was a reasonable inference to be made that the transducer being discussed was the AIRMAR P66, as it was the only one mentioned.

The Lowrance Skimmer transducer--actually being discussed--has been found to give very good results for SONAR echoes at high speed. This transducer works very well at speed. I don't have any good images to show of the mounting location on my boat. Because my transducer is on a Whaler Drive, not on the hull transom, its position would not be significant to this discussion. You just need clear, undisturbed water flowing into the transducer to get good results.

Fishmore posted 08-17-2011 09:12 PM ET (US)     Profile for Fishmore  Send Email to Fishmore     
Floater,

Because it works well while turning to either side that is an indication that the transducer is not in clean water when going straight.

Therefore you need to find a location on the transom where there is clear water while running straight. Best bet is to get the boat on plane and snap a couple of pictures of each side of the transom looking down from above (you might do the same while the boat is turning so you can compare) then analyze the water coming off the transom to see where the cleanest water is, place the transducer at that point.

The best point on my Montauk was originally on the starboard side but after installing a kicker on the starboard side the best place became just below the all around light mount on the port side.

floater88 posted 08-18-2011 07:46 AM ET (US)     Profile for floater88  Send Email to floater88     
Ok thanks for the tips guys. I'm going to remount it in a different location a little closer to the keel and see what happens. I guess drilling a couple more holes is cheaper than buying another transducer!
jimh posted 08-18-2011 08:00 AM ET (US)     Profile for jimh  Send Email to jimh     
To test for a good location, mount the transducer bracket to a short length of wood board, say a 1 x 3. Use a C-Clamp to clamp the board to the transom of the boat and orient the transducer to the test position. If the test location proves to be a good place, you can install the bracket on the transom directly.
floater88 posted 08-18-2011 06:19 PM ET (US)     Profile for floater88  Send Email to floater88     
I wish I'd read your post earler, jimh. I filled the other five holes with two-part marine epoxy today and re-drilled two new holes closer to the keel, but about a foot away from the path of the motor. Looking underneath I noticed a strake further up the hull that ends well before the transom and it was in line with the transducer mounting. When I drilled the new holes all this water came pouring out!!!! I thought those transoms were all sealed up?? I put an air hose on one of the holes and blew out all the water and i'm going to leave it like that for a few days in the hopes all the water leaves. Thanks
Fishmore posted 08-18-2011 09:20 PM ET (US)     Profile for Fishmore  Send Email to Fishmore     
Floater, your best water is usually farther away from the keel not closer to it. Definitely check the underside for any protrusions that might lead to disturbed water. Usually a couple inches one way or the other is enough to get you in to clean water.

Jim's idea on the board is an interesting idea but, make sure that the board is very secure and does not extend below the transom or your transducer might go flying off along with the board and cable with the whole mess wrapped around your prop. Maybe you should add a short leash to the board just in case.

By the way you might want to check your drain tubes for rot if you had water in the transom.

floater88 posted 08-18-2011 09:34 PM ET (US)     Profile for floater88  Send Email to floater88     
Thanks Fishmore. Where are these drain tubes? Would that be the two holes in the transom that let the water in and out of the splashwell? If it is those holes how do I get the metal off to check for rot? Thanks
jimh posted 08-18-2011 11:02 PM ET (US)     Profile for jimh  Send Email to jimh     
Please move discussion of hull repairs to REPAIRS/MODS. Thanks.
floater88 posted 08-19-2011 05:16 PM ET (US)     Profile for floater88  Send Email to floater88     
Thanks for all the help guys. I moved the trasnducer to withing 10 inches of the keel right at the bottom of the transom and it works great at all speeds now.
jimh posted 08-19-2011 08:45 PM ET (US)     Profile for jimh  Send Email to jimh     
Thanks very much for the update and additional information on the placement of your Lowrance Skimmer transducer for an HDS-7 on your Boston Whaler boat transom. I have been very pleased with the performance of my Lowrance Skimmer transducer mounted on the transom of (the Whaler Drive attached to the) transom of my Boston Whaler boat.

I have also been giving some thought to getting an AIRMAR P66 50-kHz and 200-kHz transducer for my HDS SONAR, on the basis that at 50-kHz I would be able to get stronger bottom echoes in deep water. I have a continuing interest in looking for a particular ship wreck which lies in 530-feet of water, and I think the AIRMAR P66 transducer might be better suited to give me good SONAR echoes from that depth. However, I have to say that I am very impressed with the Lowrance HDS-8 unit's ability to give strong bottom echoes in very deep water using the stock 83-kHz and 200-kHz transducer.

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