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post #1 of 3 Old 03-10-2010 Thread Starter
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Replacing Standard Horizon SL1

I need to replace my Standard Horizon SL1 knot meter and I have two questions I was wondering if anyone had some ideas:

1) I would like to keep the current housing for the transducer and not drill a new hole in the hull if possible. I believe the housing for the transducer used for the SL1 is an Airmar ST650; are the specs for either the Airmar ST850 or ST800 the same as the ST650? Are either of these transducers compatible with a Raymarine ST60?

2) Along the same lines, the SL1 was mounted with a 4" round hole, can the Raymarine ST60 be adapted to this existing hole? It looks as though the ST60 is 4-1/2 x 4-1/4 rectangle. Anyone have any experience trying to fit a rectangle into a circle?
Thanks for any suggestions!
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post #2 of 3 Old 03-11-2010
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retrofit ST60

You can download the ST60 manuals from Raymarine's website; they include the mounting template and dimensions.

While the front of the instrument is (sort of) square, the rear is round. Surface mounting the ST60 is done in a 3.54 inch diameter ROUND hole. I just measured the spare ST60 sitting on my desk (don't ask) and it would just cover a 4" round hole if you're careful about centering the gasket. The mounting screws are on 4.25" centers so they will be sitting just inside the edge of your hole. At worst you may need washers.

On a previous boat I went from SR Mariner 4" instruments to Standard Horizon which only needed a ~1.5" hole... I fit a disk and epoxied it into place; did not need any gelcoat work as it was covered by the new instrument anyway.

Another approach would be to flush-mount the ST60. You need a fllush-mount version, or a conversion kit. It then fits a 4.47"h x 4.3"w rectangular hole (with a curved bottom). That would more than cover your old opening, but personally I'd go with surface mounting the round 3.5 instrument into the round 4" hole.

Last edited by redline; 03-11-2010 at 10:17 PM. Reason: typo, add flush-mount info
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post #3 of 3 Old 03-11-2010
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Why not just call airmar or go to their website and download the specifications for the St650, ST800 and ST850 transducers.


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