Knotmeter / Depthsounder Combos - Opinions?

[davisr]

I am upgrading my electrical system and electronics for coastal cruising. The existing knotmeter and depth sounder are EMS (Electro Marine Systems) brand instruments. EMS is no longer in business. Moor Electronics in Buffalo, NY used to service EMS instruments and now makes similar replacement instruments. I could replace my EMS instruments with Moor instruments, but would end up spending more than I would if I purchased a combination instrument from another manufacturer.

From the research I have done, these appear to be my options:

1. Moor brand Knotmeter w/through-hull ($172) and Depth Sounder w/through-hull ($250). Thus, $422 total.

http://www.moorelectronics.com/sailing/sailing.html


2. Raymarine ST40 Bidata System w/thru-hull for for depth and thru-hull for speed/temp ($289)

http://www.defender.com/product.jsp?path=-1|344|295761|301233|320702|746013&id=743715


3. Simrad brand IS20 Combi w/single distance/speed/temperature thru-hull ($373).

http://www.simrad-yachting.com/en/Products/Leisure/Instruments/IS20-Instruments/IS20-Combi/

4. Northstar brand M310 Multi Display w/thru-hull for depth and thru-hull for speed/temp ($450)

http://www.northstarnav.com/Products/Instruments-Gauges/Explorer-310-Series/M310-Multi/Specifications/


5. Garmin GMI 10 Instrument Display ($500); Intelliducer depth/temp thru-hull ($178). Thus, $678 total.

http://www.defender.com/product.jsp?path=-1|344|302025|296556|321037&id=951825


6. Furuno F1-503 Display ($461); DST-800 Depth/Speed/Temperature Sensor ($283). Thus, $744 total.

http://www.defender.com/product.jsp?path=-1|344|295761|320704|320787&id=952533


7. Instead of replacing instruments install a GPS such as a GARMIN gpsmap 440s w/ US Coastal Marine Charts and thru-hull transducer for depth/temperature ($550 total) or GARMIN gpsmap 540s ($585), which is bigger with a 5 inch screen.

http://www.boatersworld.com/product/MP63499226.htm?utm_medium=cpa&utm_source=Shopping


Thanks for your help with this,
Roscoe

[Boracay]

I put the Bidata ST40 into Boracay and made the mistake of putting too much antifouling on the paddle wheel. Never been able to get a speed reading. I'll pull it out next time we haul, put in the plug, and take the time to clean it out totally.

Some thoughts:-
1) The BD40 depth works well.
2) The supplied cable in the speed unit was too short for my 44' aft cockpit boat.
3) Paddle wheels can be a total pain in the &#%*. I miss the VDO propeller/cable unit I put on my ferro boat near 40 years ago. A paddle wheel should work well on a fibreglass racing boat where it's pulled out after each race and the plug put in. I don't like any water (especially salt) inside my steel boat.
4) With GPS today speed though the water is nice but not necessary. A GPS that measures in tenths (or even hundredths) of a knot would be nice.
5) Rather than going for speed/depth if I was to do it again I'd check out those forward scanning sonars. Could be much nicer when moseying round a dicey anchorage. Given that most depth units are going to need some installation the difference in the end cost may not be that great.
6) I would have been happier with separate log and depth units.

[lancelot9898]

I was looking at your #6, but thought I might get by cheaper. Still haven't committed to a purchase yet and will probably put it off another year. I do have a functioning depth sounder, but it's 25 years old and reads just down to about 150 feet. My knotmeter quit working some 2 years ago, but I'm using a GPS for speed over ground. I liked the Furuno unit because it would fit into the instrument pod and would just take up one space rather than two. Plus the transducer would just require one hole and wire being run to the helm. I'm still unsure about that transducer housing both the depth and knot meter thinking that maybe a deciated depth finder might give more accurate results??? To me the depth finder is one of the most important instruments next to the compass aboard.

[davisr]

Boracay, I hear what you're saying about "wheels that don't paddle." My wheel is coated with thick layers of bottom paint. No telling how long it's been since it worked. The previous owner, an elderly gentleman, wasn't sure how long it had been out of service.

Lancelot, the point you make about the single transducer for speed, depth, and temperature is one that I have wondered about myself. While it is nice to have only one hole in the hull instead of two, it seems that you would get more accurate readings from independent transducers.The single transducers, however, don't appear to have wheels. Perhaps they are an improvement on the "wheels that don't paddle" problem?

In terms of the GPS . . . it seems that, as a cost-saving measure, the GPS alone (with the appropriate thru-hull transducer) would be the best choice. After all, it can provide the information that the combo instruments can provide, and, at the same time, show you your position on a chart.

Please correct me if I'm wrong here, but it seems that the primary benefit of the combo instruments is that they are easier to see/read in the cockpit, and, if they are independent of the GPS, i.e., not part of a network, they will provide redundant information (which is beneficial if the GPS should fail).

Would be grateful for additional guidance in this fellas.

Thanks,
Roscoe

[rustypirate]

The one thing that GPS cannot provide is depth information. For that you would need a networked depth module or seperate sounder.

The only real benefit I can see from an integrated depth/speed module is space savings. The power draw from the LCD units is not worth bothering over, and everything combined into one device makes for a single point of failure if the guage goes out.

In the cockpit, or at a helm station where space is a concern, they are great, but nothing beats having a backup system in the Nav station.

[forsailbyowner]

I use the furuno smartsensor triducer made by airmar. Cost $230, transmits nmea data speed depth and water temp can be dispayed on garmin gps and or furuno navpilot. Can pull it out inside for cleaning.

[Wotname]

Yes, I second the Furuno (Airmar) smartsensor - it provides depth and temp (and speed on some models) as a NMEA data stream. Connect it to what you will - I used the Furuno RD-30.

[lancelot9898]

It's good to hear that people are having good luck with that triducer that Airmar puts out for the furuno display unit. I was thinking that the paddle wheel might set up some turbulence so that the depth sensor would give errorious data at times. It's always nice to have your speed through water and compare that reading to the GPS over ground reading not to mention that there is some reduncy with two separate systems. I read some time ago about a sensor which did not use the paddle wheel to measure speed, but like with the forward looking sonar the price was too high for my budget. When I do get around to replacing the depth and speed instruments, I'll have to check to make sure that I don't need to replace the thru hull fitting too. Also need to make sure that what ever sensor is compatable with the read out instrument and that I get sufficient depth readings beyound my current max of 150 feet or so. Would like to go down to 1000 feet, but the Furuno unit falls well short of that spec. as most do.

[davisr]

So it sounds like it is indeed a good to have two separate systems: 1.) a GPS (with depth/temperature transducer) and 2.) other instruments (or a combination of instruments) that measure speed, depth/temperature. The redundancy is a desirable safety feature if one system should fail.

It also sounds like quite a few people have had good luck with the Furuno Airmar smartsensor. This is good to know. Just wondering . . . does anyone have some familiarity or experience with Simrad (option 3 in the original posting)? Sounds like the company has been around for many years. Their comb display with single thru-hull transducer is much more affordable compared to the Furuno display and single thru-hull transducer. $373 vs. $744.


3. Simrad brand IS20 Combi w/single distance/speed/temperature thru-hull ($373).

http://www.simrad-yachting.com/en/Products/Leisure/Instruments/IS20-Instruments/IS20-Combi/


Thanks for the help,
Roscoe

[davisr]

I found a helpful article by Ben Ellison, "Instruments, the New Generation," that compares some of the various multi-function instruments discussed above. Thought I'd share.

NMEA 2000 Instruments Gauges - Power & Motoryacht - Instruments, the New Generation

[Patrick_DeepPlaya]

Airmar is coming out with a solidstate (i.e. no log wheel) speed\depth\temp combo unit this year. The best answer I could out of them was 3-6 months when I asked in November 2009.

[tsampsel]

Anyone have experience with the TackTick wireless system?