I am replacing my depthsounder and speed/log and the new thru-hull transducers are over 1/2" smaller in diameter. Any ideas out there on technique?? I could cut new holes and leave the old ones there - but there must be a better solution?? Thanks!
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Jon Bastien (H25 'Adagio')
Put depth transducer inside hull?
I've read several posts in these forums that suggest you don't need to drill a hole through your hull at all- If there's no coring material, you can use epoxy or silicone sealant to attach the transducer to the inside of the hull and it should work fine. You can even test this theory temporarily by using KY jelly first, to ensure it works, before permanently attaching the 'ducer. After that, I'd just leave the old one in place as long as it doesn't leak... Not sure how to help with your knotlog transducer, though. --Jon Bastien
I've read several posts in these forums that suggest you don't need to drill a hole through your hull at all- If there's no coring material, you can use epoxy or silicone sealant to attach the transducer to the inside of the hull and it should work fine. You can even test this theory temporarily by using KY jelly first, to ensure it works, before permanently attaching the 'ducer. After that, I'd just leave the old one in place as long as it doesn't leak... Not sure how to help with your knotlog transducer, though. --Jon Bastien
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david lewis
transducer ideas
I had a 25 catalina and the depth transducer was in a "water box" inside the hull. basically a plastic box bonded to the hull inside and filled with water and the transducer was mounted to the cover of the box and adjusted to be up against the hull. It worked ok for about 10 years. When I replaced the unit I just epoxy bonded it to the inside of the hull and it worked just as well. I think the manufacturer's literature said they wouldn't guarantee this method due to boats being different but for me it worked. For your knot/log if it is a half inch smaller why not make a sleeve with two o-seal grooves to fit the existing hole? This sleeve would have a 1/4 inch wall thickness and the depth of a seal groove could be as small as 1/16 or less. If your old transducer came with a plug to allow you to pull out the transducer and plug the hole then it could be as simple as drill out the plug to the size to fit your new transducer, this way you already have a seal system designed for the existing hole. Do this on a lathe to make the hole concentric to the O.D. Retention of the transducer is another issue as the cross hole needs to be at the right height.
I had a 25 catalina and the depth transducer was in a "water box" inside the hull. basically a plastic box bonded to the hull inside and filled with water and the transducer was mounted to the cover of the box and adjusted to be up against the hull. It worked ok for about 10 years. When I replaced the unit I just epoxy bonded it to the inside of the hull and it worked just as well. I think the manufacturer's literature said they wouldn't guarantee this method due to boats being different but for me it worked. For your knot/log if it is a half inch smaller why not make a sleeve with two o-seal grooves to fit the existing hole? This sleeve would have a 1/4 inch wall thickness and the depth of a seal groove could be as small as 1/16 or less. If your old transducer came with a plug to allow you to pull out the transducer and plug the hole then it could be as simple as drill out the plug to the size to fit your new transducer, this way you already have a seal system designed for the existing hole. Do this on a lathe to make the hole concentric to the O.D. Retention of the transducer is another issue as the cross hole needs to be at the right height.
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Jack Gilmour
Epoxy works for depth
For several years I used a "transom mount" transducer epoxied to the inside of the hull on a Sun 27. It was good up to at least 200 feet whch was the max depth that my depthsounder could record. This will not work on a cored hull but few boats have them.
For several years I used a "transom mount" transducer epoxied to the inside of the hull on a Sun 27. It was good up to at least 200 feet whch was the max depth that my depthsounder could record. This will not work on a cored hull but few boats have them.
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Edmund Shanahan
Changing manufacturors
How about taking back the new ones and finding a model that has a transducer the right size for the existing hole. I assume you have contacted the manufactor and presented the problem to them to see if they offered a larger diameter thru-hull fitting, or adaptor? Sure would save a lot of work and get the job done as designed for.
How about taking back the new ones and finding a model that has a transducer the right size for the existing hole. I assume you have contacted the manufactor and presented the problem to them to see if they offered a larger diameter thru-hull fitting, or adaptor? Sure would save a lot of work and get the job done as designed for.
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Tom
Cover the existing hole
Maybe fill the entire existing hole with fiberglass & epoxy resin. Then when cured, cut a new hole just the exact size you need. Would look the best from the outside, minimizes the number of transducers penetrating the hull, as well as allowing you to keep the transducer in the same location on the hull.
Maybe fill the entire existing hole with fiberglass & epoxy resin. Then when cured, cut a new hole just the exact size you need. Would look the best from the outside, minimizes the number of transducers penetrating the hull, as well as allowing you to keep the transducer in the same location on the hull.
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Brian Ranniger
raytheon or signet
I had a similar problem when I replaced the signet tranducers in my C-30 with a Raytheon setup (actually Airmar transducers) The Raytheon was about 1/8" smaller in dia. which wasn't too bad. I just filled it in with extra 4200. Anyway, they are about 2" dia., so maybe they would work better for you. I paid 320.00 for the Raytheon ST-40 Bidata (knot/depth) with transducers at pyacht.com. Good luck.
I had a similar problem when I replaced the signet tranducers in my C-30 with a Raytheon setup (actually Airmar transducers) The Raytheon was about 1/8" smaller in dia. which wasn't too bad. I just filled it in with extra 4200. Anyway, they are about 2" dia., so maybe they would work better for you. I paid 320.00 for the Raytheon ST-40 Bidata (knot/depth) with transducers at pyacht.com. Good luck.
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