Association Forum - Knotmeter repair or replacement?

Assn Members Area · Join

Home.

Association Forum

Ships Store

Cruising

Racing

Technical Tips

Photo Gallery - New

Boat Search - Updated

Manuals & Brochures

Swap Meet

Links

Officer Flag Line & Staff

Bylaws & Constitution

Members Area

Join the Association

Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.

Association Forum

Username:	Password:
Save Password
Forgot your Password?

All Forums

Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

Knotmeter repair or replacement?

New Topic

Topic Locked

Printer Friendly

Author

Topic

Voyager
Master Marine Consultant

Member Avatar

USA
5362 Posts

Initially Posted - 02/04/2018 : 08:38:40

Like many of you I have a 30+ year old DataMarine knotmeter mounted on my bulkhead and also have a through hull transducer that could become a concern in the future. The knotmeter and paddle wheel transducer still "work", however, the ancient LCD display does not appear clearly or have any contrast. In the past I was able to improve viewability using a polarizing glass filter but that fix no longer works.

Does anybody know whether there's a circuit component in the LCD driver circuit like a resistor or a capacitor that may have failed? If so, I can replace it. Or could there be an internal control like a contrast adjustment?

If I cannot repair the meter, I'm planning to remove it. I'll put it away for safekeeping if I decide to sell Passage.

Removing the gauge would then provide me options on what to replace it with. At the moment I have two or three options:

1. Add a waterproof VHF speaker to make communications more intelligible. I have an external speaker in the cockpit seat back storage cubby, but my aging ears cannot clearly hear that speaker. A speaker mounted in the 4" hole in the bulkhead will fill the hole and add a helpful tool, however the speaker magnet could adversely affect the compass mounted only 4 feet away.

2. Patch the hole using fiberglass and epoxy or cover it with some Starboard. I can add a Chartplotter or a Tablet computer and run a navigation application. The downside of a chartplotter is cost ($450 and up) while a Tablet has weather and viewability issues.

3. I "fixed" its companion depth meter by removing the guts of the meter and fitted a smaller round display inside of the old housing. That was a great solution since I was able to maintain at least the look of the original gear. It would be great if I could similarly replace the knotmeter with a speed indicator that could fit inside the old housing.

Any suggestions on any of these options?

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Edited by - Voyager on 02/04/2018 08:42:42

Stinkpotter
Master Marine Consultant

Members Avatar

Djibouti
9076 Posts

Response Posted - 02/04/2018 : 09:41:24

Something like this? That would tell you speed over the bottom instead of through the water, and rid you of the paddle-wheel.

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

Edited by - Stinkpotter on 02/04/2018 09:41:50

Steve Milby
Past Commodore

Members Avatar

USA
5897 Posts

Response Posted - 02/04/2018 : 10:04:03

I have a "new" (never installed) Datamarine S100-KL knotmeter. It's a complete kit which even includes the owner's manual. I'd like to keep the paddlewheel transducer and the round plastic instrument cover for my own use, but if what you need is the instrument, this should fill that need. I have never tested it, but if you hook it up and it doesn't work, I'll refund your money on your say-so. Ten minutes ago I took a photo of everything except those two items. If you'd like them, make an offer that you consider reasonable including shipping cost. It might take me 2-3 days to ship them because I'm struggling with the dreaded flu.

I'm waiting for the photo to download to dropbox and will post it here when I can.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Steve Milby
Past Commodore

Members Avatar

USA
5897 Posts

Response Posted - 02/04/2018 : 10:46:17

I just noticed that your transducer still works, but you want a transducer in case yours fails. That's why I also want the transducer, in case mine fails. I'll make you a deal. I'll include the transducer, but I'll keep it for now. If yours fails before mine, I'll send it to you for the shipping cost. If mine fails first, I'll keep it and use it.

I'm still waiting for the photo to download to dropbox. It must take a looong time!

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Steve Milby
Past Commodore

Members Avatar

USA
5897 Posts

Response Posted - 02/04/2018 : 14:22:19

Here's the photo.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Voyager
Master Marine Consultant

Members Avatar

USA
5362 Posts

Response Posted - 02/04/2018 : 18:57:14

Dave, I like the GPS speedomometer. You�re right it�ll give me my actual speed and it�ll let me get rid of that through-hull.

But Steve, is the DM knotmeter like a �fresh out of the box� 30 year-old unit? Looks good. I appreciate the offer on the spare transducer but mine works just fine so long as the slime doesn�t build up on the paddlewheel. It�s just the LCD in the head unit that�s gone.

Looking at the photo it looks like the right fit. Can you tell me what the back of the display looks like? Should be a BNC bayonet connector for the transducer cable, three power terminal screws, a cal adjuster gizmo, a toggle switch.

Regarding costs, Dave�s GPS option is about $80 and eBay full replacements are about $100 with the transducer. I could take it off your hands for $90 without the housing, without the transducer, but with the booklet or a photocopy of the booklet. You can email me at Bruce2Sail at aol.com

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Edited by - Voyager on 02/04/2018 19:58:36

Steve Milby
Past Commodore

Members Avatar

USA
5897 Posts

Response Posted - 02/04/2018 : 20:15:50

Here's the clearest photo I could take with my shaky hands. When I bought it, it wasn't in the original box, but everything about it makes me believe it has never been used or even hooked up. The stainless steel trim around it has a factory shine, there's not a speck of caulk on the casing, the wires are all coiled and wrapped as if from the factory, with no kinks. The rubber o-rings that go on the transducer haven't been put on the transducer. They're still packed in a separate envelope. I believe it's brand new, not in the original packaging.

If it's ok with you, I think I'll connect it to my Cal 25 battery that I brought home for the winter, just to be sure the screen numbers come on. I'd be embarrassed to send it to you and find it dead on arrival. I'm OK with your offer. Here's the photo.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

TCurran
Admiral

Members Avatar

USA
588 Posts

Response Posted - 02/05/2018 : 06:59:14

quote:
Originally posted by Stinkpotter

Something like this? That would tell you speed over the bottom instead of through the water, and rid you of the paddle-wheel.

I like that speedo, was wondering what to fill the holes where my paddle wheel display fits. This might work. I currently use a Velocitec SpeedPuck but I'm always knocking it off and into the cabin.

Tom Curran
1981 Capri 25 Hull #101 "Dirty Debbie"
1988 Watkins 30
PAFB, FL

Steve Milby
Past Commodore

Members Avatar

USA
5897 Posts

Response Posted - 02/05/2018 : 07:36:49

I just hooked it up and the numbers lit, the backlight lit, and, when I spun the paddlewheel with my finger, the numbers changed, so it appears to be working perfectly.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Voyager
Master Marine Consultant

Members Avatar

USA
5362 Posts

Response Posted - 02/05/2018 : 07:52:02

Tom, I�m not sure about the size and configuration on the knotmeter but I was able to remove the entire guts of the depth meter on Passage and saved the metal housing and the glass face. I removed the metal disc of the backing plate from the guts and had a pretty good enclosure for my replacement Hawkeye depthmeter. There was a small 1/4� or 3/8� hole in the front of the glass where a toggle switch was mounted, but I filled that with a dab of silicone or caulk.
I don�t know whether you could modify the existing enclosure to accommodate the speed puck. If so, you wouldn�t have to fill the hole.
Another approach is to take out the old unit and mount a piece of Starboard sheet over the hole. You could either mount the speedo to that or drill/cut a hole in it to accommodate the puck.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

TCurran
Admiral

Members Avatar

USA
588 Posts

Response Posted - 02/06/2018 : 07:02:05

quote:
Originally posted by Voyager

Tom, I�m not sure about the size and configuration on the knotmeter but I was able to remove the entire guts of the depth meter on Passage and saved the metal housing and the glass face. I removed the metal disc of the backing plate from the guts and had a pretty good enclosure for my replacement Hawkeye depthmeter.

Thanks Dave, that's a pretty good idea, will have to see if it's feasible with my setup. I have both a, old paddle wheel display and depth gauge. The depth gauge is pretty useless, the transducer is being the keel. I know the depth when the keel hits...hahah. They're both 4" Signet gauges and mounted in the step into the cabin. I use 3m dual lock tape to hold the speed puck on the cabin hatch, which I always seem to hit. But I do like it there, I can see it without looking down.

I might be interested in one of the GPS speedo like the one in the link if I can swap out with little modifications, if not, I'll continue abusing the speed puck till I kill it.

Tom Curran
1981 Capri 25 Hull #101 "Dirty Debbie"
1988 Watkins 30
PAFB, FL

Voyager
Master Marine Consultant

Members Avatar

USA
5362 Posts

Response Posted - 02/06/2018 : 20:59:10

Steve, ping me on email for snail mail addresses.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Steve Milby
Past Commodore

Members Avatar

USA
5897 Posts

Response Posted - 02/08/2018 : 14:32:27

quote:
Originally posted by Voyager

Steve, ping me on email for snail mail addresses.

Bruce, I sent you an email. I'm in Georgia at the moment. I'll be home late tomorrow or Saturday, and, after tonight, probably won't be online again until I get home.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Voyager
Master Marine Consultant

Members Avatar

USA
5362 Posts

Response Posted - 02/08/2018 : 14:57:24

Steve. Ok. I got your email through the forum that listed your snail mail address and your personal email address. I sent a response to your email account. I sent you my street address in the response. If you can, just email me again at Bruce2Sail at Aol dot com. I�ll email you again. I put the check in the envelope and it�s sitting in my mailbox with the flag up. I think we should be all good now.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Voyager
Master Marine Consultant

Members Avatar

USA
5362 Posts

Response Posted - 02/08/2018 : 15:07:34

Oops!!! Looks like my email failed to launch the other day. Copy/paste of email addresses apparently does not work on my iPhone. Live and loin!!

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Steve Milby
Past Commodore

Members Avatar

USA
5897 Posts

Response Posted - 02/08/2018 : 16:11:01

quote:
Originally posted by Voyager

Oops!!! Looks like my email failed to launch the other day. Copy/paste of email addresses apparently does not work on my iPhone. Live and loin!!

I just got your last email.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Voyager
Master Marine Consultant

Members Avatar

USA
5362 Posts

Response Posted - 07/01/2018 : 08:39:54

@ Steve,
Following up on the knotmeter you provided. I installed it in the bulkhead on Passage in place of the previous 32 year old unit. Old one came out easily enough and the �new� one fit like a glove. I gobbed it in with polysulfide caulk.
So now, the only problem is that the digits are so clear that I need to replace my depth meter right alongside!!!
I tried to calibrate it against my GPS passing up and down reversing my course (to negate the effects of current) and I�m tweaking it into cal over time. I think there might be some kind of settling that needs to occur.
All good. Thank you Steve!!!

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Steve Milby
Past Commodore

Members Avatar

USA
5897 Posts

Response Posted - 07/01/2018 : 10:46:23

You're welcome. I hope it lasts 32 years, like the one it replaced.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

RichardG
Admiral

Members Avatar

USA
990 Posts

Response Posted - 07/02/2018 : 11:53:11

While your problem is fixed, this is a reoccurring issue on older boats. As an alternative, years back I made a porthole by removing the guts of an old non-fitting dial knotmeter, cutting the housing to just under-flush inside, then gluing it back in. Then made a round teak molding piece for the inside. Still looks good.

RichardG 81 FK/SR #2657
Terminal Island, CA

Voyager
Master Marine Consultant

Members Avatar

USA
5362 Posts

Response Posted - 07/02/2018 : 18:21:47

Richard, that�s a great idea. Better than having an unsightly hole.
The unit looks great and works well except that the reading is about 25% shy of my GPS reading (irrespective of tidal current) and the adjustment knob cannot adjust the reading to be high enough. It�s possible that my paddle wheel speedo is not the matched unit for the instrument or the circuitry is old and may require an electronic part (electrolytic capacitor) to be replaced.

This circuit may work in one of two ways:
1. Analog - frequency counters relied on a simple RC circuit charging a capacitor. If the cap dried out (as is a common failure mode), then the meter will read low.
2. Digital - it the unit uses a TTL or CMOS flip flop circuit with a reset for each time the paddle wheel spins, then if it�s a wrong sensor, then the counter will mis-count.

Luckily I still have the old unit so should be able to compare their internal electronics.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Topic

New Topic

Topic Locked

Printer Friendly

Jump To:

Association Forum

Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.