Martin,

Just last week I had my old knotmeter replaced with a new Speed/Log meter. I really wanted the convenience of a transom-mounted xducer, but was discouraged from it by, well, everyone, for the reasons you've cited--irregular flow, heeling, obstructions, stern-side hazards, etc. I don't like having holes in my hull, but the previous owner had come to the same conclusion about the best type and had already put a thru-hull in for the old, and I mean OLD, xducer.

The previous hole was larger than the new standard diameter, so I had it done at a nearby (two hours away) boatyard, along with some other work (at this point in my neophyte experience with boats, my philosophy is that I want to do the cosmetic, interior, and accessories stuff, but I let the pros handle things structural.) The old hole was epoxied over and back into the core some, then they drilled through the epoxy to the correct size (just like they say to do for laminate protection.)  He also told me that the old bedding had deteriorated so much he was surprised it hadn't leaked, but it had probably been untouched for over ten years. 

Speaking of plugs, that's where I got the shot ballast that is now immortalized as a picture on the MSOG site in "Flotsam and Jetsam" under "How-to".

The transducer is placed just forward of the battery about 8 inches and maybe a couple of inches off the battery's right side towards the centerline. It needs to be easily accessible for switching out the transducer unit with the blanking plug for trailering. And if it's out of the water at that location, I suspect boat speed will be the least of my worries. The previous owner told me the old knotmeter transducer kept going bad, then I sent it in for repairs and it lasted a year before dying, then I found out, duh, that one MUST remove the impeller unit while running down the road, which I should have known, but only suspected. They don't register 70 mph too well.

I assume it's standard on the 17s, but just in case, my battery's under the left side of the V-berth next to the v-berth bulkhead.

The previous owner also had a thru-hull for the depth sounder, a separate unit, which I had a repair guy take out and epoxy in the hole. It made a perfect place to mount the new fish finder transducer that signals from inside the hull, no hole needed, and I KNOW it's solid fiberglass (and works). Because it's in an area where stuff gets shoved back and could get roughed up, I stood a 3" length of 4" diameter PVC pipe up around it. It is mounted about halfway back between the companionway and the transom, under the cockpit just to the right of the keel/bilge, maybe 6 inches off. I'll get measurements if you want.

I think I've just about made myself believe that my distrust of thru-hulls is unfounded, if it's installed right and inspected every year. After all, the big boats have them as a matter of course.

For what it's worth.

Also, I just received some mast crutch pictures from Tod and Steve Parsons. I'll have them up in an hour.

Doug


At 09:13 PM 4/23/02 +0000, you wrote:

I'm planning on mounting a speed/depth sensor to my 1976 M17.   I'm concerned about the effect of heeling and potential for turbulence from the cockpit drain.  Any advice would be appreciated.

thanks, Martin

Duluth, MN


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Doug King
M-17 #404 "Vixen"

Montgomery Sailboats Owners Group Web site: http://msog.org
Email: mailto:msog@msog.org