Repairing Speedometer

[The Dog House]

I have a Standard Horizon Speedometer (Model SL30) that isn't working. I contacted Standard Horizon to try and purchase a replacement paddle wheel hoping that would fix the problem, but I received a reply that parts for the SL30 have been out of production for over 10 years. The unit turns on and seems fine but constantly reads "0". Any ideas where I can start troubleshooting?

[Flyboy]

Don't waste your time and money, buy a GPS Speedometer from Defender, www.defender.com. Will give you your actual speed across the water, has built in GPS antenna for 89.99. I put one in my boat and it works great!!

[The Dog House]

Don't waste your time and money, buy a GPS Speedometer from Defender, http://www.defender.com. Will give you your actual speed across the water, has built in GPS antenna for 89.99. I put one in my boat and it works great!!

I already have a GPS on the boat for ground speed. The problem is I boat on a tidal river with up to a 3 mph current. My ground speed will vary anywhere from 15 mph to 21 mph (18 mph + 3 mph). The boat seems to run best at 18 mph through the water, so it would be nice not to have to guess how much to add or subtract. I've been getting by without a through the water speedometer, but it would be nice to have one if I can get the one on the boat working for not much money.

[Big D]

It's important to note if it's actually spinning of course but it must also be clean for it to work properly. They contain a Hall Effect sensor in them and a magnet in every blade of the wheel. When a blade passes by the sensor, it creates a pulse that gets counted by the computer, the number of pulses counted over a specific time reference is used to calculate speed. If the unit is really dirty externally, the sensor may not generate a pulse.

These are voltage sensitive so any voltage drop in the supply and signal voltage will affect performance too. Check connections and plug pins for corrosion. Other than the above, there's not much else you can do short of getting a schematic and taking some measurements to see if pulses are actually being generated. The lack thereof though can be due to a failed computer or speed sensor.

[The Dog House]

It's important to note if it's actually spinning of course but it must also be clean for it to work properly. They contain a Hall Effect sensor in them and a magnet in every blade of the wheel. When a blade passes by the sensor, it creates a pulse that gets counted by the computer, the number of pulses counted over a specific time reference is used to calculate speed. If the unit is really dirty externally, the sensor may not generate a pulse.

These are voltage sensitive so any voltage drop in the supply and signal voltage will affect performance too. Check connections and plug pins for corrosion. Other than the above, there's not much else you can do short of getting a schematic and taking some measurements to see if pulses are actually being generated. The lack thereof though can be due to a failed computer or speed sensor.

Thanks Big D. That's the type of information I was looking for. The wheel is spinning freely but does have a layer of river mud coating it. I'll try cleaning the wheel and the housing and see if that helps. I'll also check all of the connections for corrosion and clean if necessary. It would be nice if I could get this working with just a little elbow grease.

[Big D]

Check eBay once in a while, you never know. Someone always trying to get rid of older gear which is good news for those of us that can't keep spending money on updating every 5 years.

[horhay1946]

I have a paddle wheel speedometer on a trailer boat. The spedo stopped working and I could not figure out why. When I looked under the boat I could see the wheel with one paddle hanging down. On further investigation I found that one paddle was broken off and the wheel would only turn 1/2 revolution and then stay there.

[Flyboy]

Have you looked inside the case the speedometer is in. It looks like something from the first mission to the moon, 3 layers of circuits, diods, transitors, and all kinds of top secrete stuff. If it is not the paddle wheel or power to the system, good luck. Keep us posted.

[The Dog House]

I checked out the speedometer and paddle wheel today. The electricity, etc. going to the speedometer seems good. I measured the dimensions of the paddle wheel and they were an exact match to the Airmar 33-110 speed paddle wheel ( https://shop.meob.com/products/airmar-3 ... 1936677447 ). I ordered one today. After I receive it I'll install it and test it on the trailer.

[The Dog House]

I installed the new paddle wheel today. I spun it by hand and quickly climbed the ladder to look at the speedometer readout, but the reading was zero. The engine was not running so it was just powered by the onboard battery. Hopefully either the wheel was slowing down before I could look at the readout or the voltage using just the battery was too low. If nothing else, I eliminated the paddle wheel as the possible source of the problem. Once I launch the boat in May I'll find out if I need to keep looking for the source of the problem.