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Thread: Gauges!

  1. #1

    Default Gauges!

    Boat has lots of gauges, engine room, helm, Flybridge and a Maretron system that lets a PC or dedicated screen show gauges.

    Problem is some do not work at all. And some read inaccurate


    Engine room tachometer is mechanical and the cable is cut. helm and PC tachometer reading seems good.
    Engine room oil pressure is mechanical and seems to be the only accurate reading on boat, helms and PC read real low.
    Engine room water temp is accurate but rest of gauges read too low.

    There are several disconnected senders on the engine, would these be for me or a mechanic to check with an ohm meter? They seem to be on currently un-gauged items like fuel pressure. Wondering how I would know what a good or bad reading is, could possibly check one engine against the other if I am trouble shooting? Would like to label them with expected reading.

    How do I go from where I am now to having trust worthy results at each location?

  2. #2
    Join Date
    Nov 2009
    Location
    temecula, ca., usa
    Posts
    2,614

    Default Re: Gauges!

    Well........I thought about this for a while and then.....my head EXPLODED!

    No, really, I can tell you there is one thing I would NOT change and that is the mechanical gauge for the oil pressure in the engine room. In the shop TODAY the gold standard for verifying electronic gauge accuracy is to remove the electric sender and temporarily substitute with a mechanical gauge. Yes, they too can go bad and they aren't even as accurate as some modern transducers. But they are, for the most part, extremely reliable.
    For all others....

    The Maretron system I'm not familiar with.

    It will be difficult to troubleshoot any of the electrical stuff without a base knowledge of the values that the manufacturer set everything up with. The transducer (sender) and gauge are matched but not all manufacturers use the same strategy. The senders can be ohmed but without the resistance strategy for each gauge, you are shooting in the dark unless you have known, accurate, like gauges to compare to. Taking the guages out of their mounting, reading the manufacturer info on them and then contacting them would probably be the only RELIABLE way of sorting out what you have there. You could already have MIS-MATCHED gauges and senders and not know it.

    If you have the money and time, new sets with dual senders to feed helm and ER gauges might actually be the easiest way to go. And, all wiring to the helm should be LOAD TESTED to ensure that the information is reliably transmitted to the console. This is easier to do than it sounds and I will explain how to do it if you need me to.

    OHM testing wiring is NOT a reliable test for determining if a circuit is capable of carrying a usable signal. You could install all new gear and, if the wiring isn't up to snuff, you won't get good results. The sad truth is that most wiring jobs on boats are done with little care as to proper routing and stand off to prevent chafing and breakage and it can go bad in a short amount of time. Because, it is in constant motion even just sitting at the dock. I have read accounts of clothes, hung on hangers in a closet, rubbing holes through the shoulders on a bobbing boat.

    Time is money and many installers are just interested in the money. The wiring is mostly hidden so the job can look slick and clean without actually being so. Gotta check it!

  3. #3

    Default Re: Gauges!

    JGMO,

    "all wiring to the helm should be LOAD TESTED to ensure that the information is reliably transmitted to the console. This is easier to do than it sounds and I will explain how to do it if you need me to"

    Would appreciate it if you could give me the step by step, I am suspecting that this could be one of the issues as it seems the fly bridge readings are lower then the helm, which are lower then the engine room, so the farther from the engine the farther off the gauges....perhaps.

  4. #4
    Join Date
    Nov 2009
    Location
    temecula, ca., usa
    Posts
    2,614

    Default Re: Gauges!

    Oh....a fly bridge too?? OUCH! That is a LOT of wiring! I hope you have "under dash" access. Most newer boats are built with tilt up panels that allow you to get to the connections for the gauges. But, many older boats are like cars....you have to take things apart or crawl up under only to find a multi-colored "spaghetti plate" of wiring going every which way.

    Chances are, if the wires in the fly bridge are the same DIAMETER as the wires in the engine room....that alone could explain some signal loss. The longer a "run" wiring has to make, it needs to me "upsized" so as not to provide too much internal resistance.

    Here's an example of what I mean:
    The wiring in the engine room, say, is 16 AWG
    The wiring going to the helm might need to be 14 AWG
    And the wiring to the fly bridge might need to be 14 AWG or even 12 AWG

    Where 16 AWG is a smaller diameter wire and the wire size INCREASES as the number goes down.

    All that in order to keep wiring "run" resistance down and allow the signal to pass through undiluted.

    Ok, gotta run...that's today's "tutorial on wires"...It never hurts to know the basics about this stuff and I included it IN CASE you didn't already.

    Finding the wires and how they are routed...along with what sizes of wires were used will be helpful in getting to the next steps. IE: locating connection points on bus bars and cleaning each contact to "shiny bright".

    Load testing will require that you know where these connection points are and that you can get to them.

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