Suitable replacement for old 1976 thru-hull B&G speedo propeller? Ideally a depth sounder or combination speed and depth?

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leakysump

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I would like to use the thru hull fitting that takes a 1976 B&G speedo propeller, with a modern replacement ideally a depth sounder or combo depth /speed. All B&G electronics died long ago. I don't want to drill a new hole in the hull just use the existing housing. Any ideas?
 
When I replaced a 1984 B&G log the new B&G log and depth (Airmar) was smaller in diameter. I have some doubts that there are any large diameter ones out there. It was easy to mount the new one in the existing hole, just tape up the outside and fill with epoxy.
 
Thanks. So you just pulled the speedo propeller thing up out of the thru-hull housing (as one did for cleaning propeller) and then push back in an Airmar of close enough outer diameter and epoxy in? Sounds good. I take it best to leave the 2 B&G depth transducers glassed in to the hull untouched since the Airmar unit is dual purpose Speedo w/ Depth Sounder?
 
I wonder if Airmar do a speedo/depth combo that is compatible with my Standard Horizon CP300i chart plotter display - I will check with Airmar tomorrow. I think it may require me to buy the SH FF520 50/200kHz Black Box Fish Finder as an intermediary process to get depth signals to the CP300i display. It might be cheaper and simpler to get a stand alone dual display for Speed and Depth. My other system is a Raymarine SPX-30 controller (for a self steering ram) which I think can process Depth and Speed input/output but probably not a combo mode input?
 
leakysump said:
Thanks. So you just pulled the speedo propeller thing up out of the thru-hull housing (as one did for cleaning propeller) and then push back in an Airmar of close enough outer diameter and epoxy in? Sounds good. I take it best to leave the 2 B&G depth transducers glassed in to the hull untouched since the Airmar unit is dual purpose Speedo w/ Depth Sounder?
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I think the idea is to remove the entire unit including the housing then blank of and fill the hole with reinforced epoxy then drill a new hole for the smaller unit. Should you epoxy in a new transducer in the existing housing it will eventually foul and fail to read and you won't be able to extract it and clean it.
 
Ah well in that case it is not a solution I am looking for - if I have to drill a hole through the hull regardless , the existence of the old B&G fitting is irrelevant. I want to use the existing 1976 B&G cylindrical housing for their withdrawable speed log propeller, and fit a modern speed/depth combo transducer (or worst case just a depth transducer alone) to slot into that cylinder. I can make some mods as have workshop with lathe etc, and I would like to know if there is a preferred go-to solution. I mean there must be literally thousands of sailboats built in the 1970's with these B&G speed log fittings...
 
leakysump said:
Ah well in that case it is not a solution I am looking for - if I have to drill a hole through the hull regardless , the existence of the old B&G fitting is irrelevant. I want to use the existing 1976 B&G cylindrical housing for their withdrawable speed log propeller, and fit a modern speed/depth combo transducer (or worst case just a depth transducer alone) to slot into that cylinder. I can make some mods as have workshop with lathe etc, and I would like to know if there is a preferred go-to solution. I mean there must be literally thousands of sailboats built in the 1970's with these B&G speed log fittings...
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I suspect that the majority have been replaced by now. My boat is on its third through hull fitting now since the mid 70's. Luckily they have all been of a similar diameter.
 
Well it is obvious that B&G had their own agenda, having dominated the UK market in the 1970's , not to support retrofitting new technology to their existing thru-hull fittings. How easy would that be at design stage! Even in the 2000's they did not want to know about stuff 25 years old and I for one will never ever buy a B&G system again
 
leakysump said:
Ah well in that case it is not a solution I am looking for - if I have to drill a hole through the hull regardless , the existence of the old B&G fitting is irrelevant. I want to use the existing 1976 B&G cylindrical housing for their withdrawable speed log propeller, and fit a modern speed/depth combo transducer (or worst case just a depth transducer alone) to slot into that cylinder. I can make some mods as have workshop with lathe etc, and I would like to know if there is a preferred go-to solution. I mean there must be literally thousands of sailboats built in the 1970's with these B&G speed log fittings...
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It's very easy to enlarge the existing hole with an oops adapter, what's the problem?
 
Its very easy to drill holes in the hull with a proper hole saw too - what's your problem? As the OP I said I do not want to drill holes in the hull,
 
leakysump said:
Its very easy to drill holes in the hull with a proper hole saw too - what's your problem? As the OP I said I do not want to drill holes in the hull,
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You already have a hole in the hull you would just be enlarging it to take a current generation transducer.
 
And inner diameter of thru-hull fitting 40mm into which the paddle wheel sensor inserts - I wonder if the B&G fitting's inner diameter is close to that? I will take some measurements over the w/e. Thanks Tranona!
 
I would contact Airmar direct as they more than likely made the B and G unit and have a direct replacement available.
I had to do this for our 1999 B and G log which was damaged by a lifting strop and identical spares were unavailable.
 
Sadly Airmar was only started in 1982 and have nothing to fit easily - they think B&G probably made their own in the 1970's.
 
leakysump said:
Well it is obvious that B&G had their own agenda, having dominated the UK market in the 1970's , not to support retrofitting new technology to their existing thru-hull fittings. How easy would that be at design stage! Even in the 2000's they did not want to know about stuff 25 years old and I for one will never ever buy a B&G system again
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And what about the companies that went bust. Seafarer and Stowe with their own design hull fittings, etc come to mind.
 
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