Ask JackRabbit

Odd Readings on P79 In-Hull Transducer

Bob: I recently purchased an in-hull P79 depth transducer from you and it works quite well with one exception.  It seems that quite often when I am in shallow water, for example a channel into a marina, the transducer indicates a dept of 1.2 feet.  Sometimes this reading is for a very short, momentary, time and it goes back to the actual reading right away.  Other times it reads 1.2 or 1 until I get out of the channel and increase my speed.  Since there are no under-water appendages that could pick up debris and block the signal, I was wondering what would cause this mis-reading of the depth?

JackRabbit: Does it do this when you are stationary in a channel, or only underway?

If it is only when underway then what is probably happening is that the transducer is reading a return signal from turbulence under the hull. It may be that the location that you have chosen is one that is subject to turbulence from some hull projection or shape. When you accelerate, that cleans up the water flow.

You could try relocating the transducer. You can try out new locations by sealing the transducer to the hull using KY Jelly and having someone hold it there while you move down the channel. The best location is going to be, in general, somewhere near the centerline but just a short distance either side.

Your transducer is a smart NMEA 0183 model and they have good noise filters built into the software. In deep water it's easy to tell the difference between the main signal and reflections from turbulence as they come back at very different times. But in shallow water, the return signal from turbulence can come at almost the same time as the 'real' return from the bottom, and it's not so easy to filter that out.

P79 Fishfinder Transducer for Garmin

Gerry: I am looking to get a P79 transducer that is compatible with Garmin.  Is Garmin's in hull transducer the same as the P79?  If not, what is specific to the P79 and how do I specify the one I need?

Thanks!

JackRabbit: The P79 is an in-hull fishfinder dual-frequency transducer rated at 600W. It's made by Airmar. As with all Airmar transducers, there are multiple models produced, each one with an interface cable and connector which is specific to a manufacturer. The P79 can be ordered with a 10-pin Furuno connector, a 6-pin Garmin, 7-pin JRC/Simrad, 10-pin Northstar, 6-pin Navman/Northstar, 6-pin Raymarine, or just spade connectors.

Just to make things even simpler, the P79 is also sold as a depthsounder with standard NMEA 0183 or NMEA 2000 output. Remember, depthsounders just measure depth and put out numeric values at regular intervals. Fishfinder transducers output a continuous stream of analog data that has be be interpreted by a sounder module.

Garmin part number 010-10327-00 is the P79 fishfinder transducer with a Garmin 6-pin connector.

NMEA 2000 Data from Small Yamaha Outboard

John: I have a question that I was unable to find an answer to on your website, maybe I missed it?

I have a Nimble Kodiak motorsailor with a 2008 Yamaha F20 ELR (20 HP four stroke, electric start, remote control) in the motorwell.  I am wondering if there is any way to get engine rpm data (tachometer) or the low oil pressure & overheat lights to work on my Lowrance LCX 27C with the “red connector” NMEA 2000 network.    Also, are you aware of any NMEA 2000 fuel level gages that would work in a portable 6-gallon fuel tank?

Thanks in advance for any help!

JackRabbit: There are two ways to get data out of a Yamaha outboard. If the boat has a CommandLink network  installed, you can tap into that. If not, you can install the Lowrance engine interface on those engines capable of handling it. The F20 is not on that list - the F50 is the smallest engine listed.

For the fuel gauge, if you can find a conventional sender that would fit there are adapters that would convert the output from the sender into an NMEA 2000 message. The problem with a portable fuel tank is that it is, well, portable... You are going to have to undo connections each time you fill it. You might be better off just picking up the tank and judging the weight like the rest of us do.

Airmar PB200G Availability

John: OK, so July has come and gone and Airmar ‘s PG200G N2K-capable weather station is still listed as  “…expected to ship at the end of July….”.

Not that I fault the Jackrabbit website; at least one may infer that the product remains unobtainable. Heck, Airmar’s own website doesn’t even list the product yet….

The situation with this product seems to give a whole new (and apt) meaning for the popular and pejorative description of an announced but phantom (software) product: “airware”…

But hope springs eternal. Any update on the new availability schedule for this line of products?

JackRabbit: Gemeco, the Airmar distributor, tells me that they expect the first delivery when it arrives. That has been expected to be in a 'couple of weeks' for some months now. It's a complex device and there's a lot of hardware and software to integrate. Bottom line : no-one knows.

The JackRabbit website has been updated to reflect this.

Yamaha Engine Interface to Lowrance LCX-111C HD

Ryan : I have a Lowrance LCX 111c HD and recently integrated the Yamaha Engine Interface Cable.  Where do I navigate to see the information from the engine?  Is there a set-up involved...etc???   Thanks in advance! Have a great day!

JackRabbit: My first thought on reading this question was that the answer was a simple one that's immensely popular among technical support personnel, though rarely voiced to customers: RTFM! Which of course stands for 'Read The Effing Manual'. Open the manual to the index page, run your finger down until you get to what looks like a likely entry, turn to that page...etc.

But for Ryan that's not the right response. I did download the manual, and ran my virtual finger through the whole document using Adobe Acrobat's search feature - and nothing. The LCX 111C HD does not display engine data. It has an NMEA 2000 interface but does not seem to do much with it. It's a discontinued model and I guess it was launched before Lowrance started offering that capability.

But the display of engine data is not a hardware function, it's a software function. As the LCX-111C HD has an NMEA 2000 interface then making it capable of reading engine data is just a question of upgrading the software. Could it be, I asked myself, that Lowrance has released a software upgrade? Has Ryan perhaps been a little lazy and not checked for this? So I went to the Lowrance site and clicked on 'Downloads' and there it is - version 2.1.0 has what he needs.

Get a blank SD card from just about any store (even CVS has them), download the file from the Lowrance site to this card, put the card in the display, boot it up and the software will upgrade automatically. Lowrance has not posted an updated manual so you'll have to poke around in the system menu or networking menu to find the right setup screens.

SmartCraft on Cummins QSC8.3 Engines

Don: I tried to subscribe to the Ask Jack Rabbit system but every time I typed in the text on the screen it said it was invalid and displayed a new text box for me to enter.  I am sure I was typing in the right letters.

My question has to do with Cummins QSC8.3 engines on a Sea Ray boat.  We are trying to develop a system to remotely monitor the boat's on board systems including engine parameters.  I am an electrical engineer but very new to the marine industry and its standards and proprietary systems. This engine is monitored by the Smartcraft system. Is there any way to get at the engine data?  I take it that it is all coming from the engine as a smartcraft specific data protocol but I wanted to check.  Is there any other way to monitor these engines parameters so we could send them by a datalink to a remote location?

Thank you.

JackRabbit: The e-mail subscription service is from a company called Feedburner that works with a lot of different blogs. It's owned by Google.  I've only had one other person complain about this issue and he was a lot less polite than you. Downright nasty, in fact. I'll see what Feedburner can advise to make this easier to use.

SmartCraft is a proprietary network protocol managed by the Mototron division of the Brunswick Corporation, a boatbuilder and engine manufacturer. The engine data can only be read by instruments that have been approved by SmartCraft. You can see a list here on the SmartCraft site. SmartCraft does not publish its protocols, and I don't know of any way to export this data from instruments that will read it.

I'll send you a personal e-mail with the contact information for the product manager for the network, and you can ask him if he has any suggestions.

Saving Power on a SeaTalk Network

Chris: Thank you for answering questions for us on your site, makes me feel better. I have three ST60 Graphic displays I was hoping to connect to a Airmar NMEA tri-ducer and a Raystar GPS. I wanted to have a system to run when I conserve power. Can I get it to show wind with the chart plotter off? What will work with the chart plotter off?

I've been trying to tackle this for a while and I'm stuck.

JackRabbit: The ST60s are powered from the SeaTalk cable. That cable contains three conductors: red is power, yellow is signal and bare is ground. In most installations, the SeaTalk bus is connected to a chartplotter or autopilot, and the power to the network and all the instruments on it comes from that chartplotter or autopilot.

What you need to do is take the SeaTalk cable that goes into the chartplotter, cut it and then splice together just the yellow and bare wires. Don't connect the red wire. Then extend the red wire (on the side of the cut away from the chartplotter) and run that to a DC breaker somewhere. Turning on that breaker will power up your instruments without using the chartplotter.The yellow and bare wires preserve the data connection to the chartplotter for when it is switched on.

Make sure that the Raystar GPS is wired up in SeaTalk mode and connected in to the Seatalk bus (not directly to the chartplotter) so that GPS data is available with the chartplotter off.

Spark Prevention for Diesel Engines?

Alan: after reading your 7/9/08 posting regarding alternator size, it brught a question to my mind. is spark prevention required with diesel power and no gasoline equiptment on board?  the cfr's only address gasoline power. am i missing something?

thanking you in advance,

JackRabbit: Diesel is not flammable at normal temperatures. It's combustible, but diesel engines have to compress it to a high pressure to get it to burn. So ignition-protected devices are not required in diesel engine rooms.

That does not mean that you can't set diesel alight if you try hard enough (the image shows a diesel fire). But a few sparks won't do it. At normal temperatures, there's no cloud of flammable vapor as there can be in a gasoline environment.

To quote Wikipedia:

"The flash point of a flammable liquid is the lowest temperature at which it can form an ignitable mixture in air. At this temperature the vapor may cease to burn when the source of ignition is removed. A slightly higher temperature, the fire point, is defined as the temperature at which the vapor continues to burn after being ignited. Neither of these parameters is related to the temperatures of the ignition source or of the burning liquid, which are much higher."

The flash point of gasoline is below -40 deg F so it is always ignitable at normal temperatures. The flash point of diesel is above 143 deg F.

I keep meaning to put some bigger inspection ports in my diesel tanks, and I keep telling myself that I can cut a hole in the top of the aluminum tanks even with fuel in there. There's really no danger. I just haven't actually been able to bring myself to do it yet.