Boat speed gauge or sending unit?

[Clydo]

Anyone had a problem with these? Have 2003 Catalina C310 M25 XPB engine 590 hours. Did
not use boat for about four months. Went out couple weeks ago boat speed gauge blank.
All other instruments worked. Had guy pull paddle wheel said some gunk on it but cleaned.
Went out again no movement on boat speed gauge for about two minutes then registered
.2 then went blank.

Went out last week no movement for about ten minutes then started showing numbers
decimal point first then at steady 2,000 RPM read .35, .34, .22, .37, .28. Trip reading from 10, 11,12, 13 14,
about every 200 feet. Shows total trip around 25, 000 NM. Appears getting signal from sender. Wondering if sender and not
gauge? Original instruments. Fresh water so no critters.

Appreciate thoughts.

Clyde Thorington
C310 # 245
I LEAN TOO
San Jose, CA

 

[Davidasailor26]

It’s pretty common for those paddle wheels to get fouled or slime growth that slows them down. I’d pull it again and try spinning it while you watch the display. My bet is on either some slime inside the paddle wheel housing, or maybe enough growth on the bottom around that area to slow the water in the boundary layer.

 

[SJN]

Hello! Dvaidsailor26 is correct. The transducer wheel must be cleaned at the bearing as well as within the unit. Pull the transducer, take it apart, clean all wheel, bearing and housing surfaces, and it should be fine for a few months. You will need a small punch to take the "axle" out.

Using your boat as much as possible will lessen frequency to clean the unit when it has been sitting. What a nice problem!

 

[JRT]

First time I cleared mine was pretty nerve-wracking with water immediately shutting in! Have that cap ready to screw on and be sure to not force or cross thread it.

 

[PlaneTom]

Clydo, when you say speed gauge was blank, was there nothing at all on the display? I'll be honest, it's been a long time since I checked it without the boat moving, I can't remember if it reads 0.0 or goes blank.
Cleaning the transducer is a good first step, and as mentioned spin the wheel by hand and see if you get a reading on the display. I did find some brush on antifouling paint made for transducers, it hasn't been on long enough to report on results.
Raymarine tech support did give info on readings to take from the instrument through the transducer, mine was faulty. On my transducer, the wires are solidly mounted into the transducer body, the new one comes with a long wire harness to reach back to the instrument in the cockpit. Stringing it through the bilges was the easy part, getting it up through the tubes into the binnacle was tough. I imagine they build it that way to avoid wire connections in the bilge.

 

[Clydo]

Clydo, when you say speed gauge was blank, was there nothing at all on the display? I'll be honest, it's been a long time since I checked it without the boat moving, I can't remember if it reads 0.0 or goes blank.
Cleaning the transducer is a good first step, and as mentioned spin the wheel by hand and see if you get a reading on the display. I did find some brush on antifouling paint made for transducers, it hasn't been on long enough to report on results.
Raymarine tech support did give info on readings to take from the instrument through the transducer, mine was faulty. On my transducer, the wires are solidly mounted into the transducer body, the new one comes with a long wire harness to reach back to the instrument in the cockpit. Stringing it through the bilges was the easy part, getting it up through the tubes into the binnacle was tough. I imagine they build it that way to avoid wire connections in the bilge.

On first trip when boat moving screen blank. Nothing on display for speed.l When switched to other readings did show miles
traveled to date. Haven't had chance yet to pull paddle wheel again take apart and clean. Good idea to check
with RayMarine. Thanks all for your thoughts.

Clyde Thorington
C30 # 145
ILEAN TOO
San Jose, CA