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Tach-Engine Hours

One of my winter projects is to replace my erratic tachometer that also has the engine hour display on it,  on my 2004 250FV. I have found a brand new identical tach, but my question is,  does anyone know if the engine hours are stored in the tach or in the PCM (computer)? Hence with a new tach, will I read 0 hours or will my accurate engine time still be displayed?
  Thanks in advance 
2004 250 FV 

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    212rowboat212rowboat Member Posts: 2,591 ✭✭✭✭✭
    edited January 2014
    Technically, its stored on both, but separately.. trust the pcm..

    You can overdrive the meter on the tach with an oscilloscope.. its easier to do with one smart enough to set a timer.
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    BruceBruce Member Posts: 167 ✭✭
    Thanks for the input, but I'm still confused, do you know if when I install the new tach if it will read the 0 hours or the actually hours on the boat?
      Thank you
    2004 250 FV 
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    212rowboat212rowboat Member Posts: 2,591 ✭✭✭✭✭
    it will read 0.... the tach, that is...

    the PCM will know the true hours... the PCM doesn't converse with the hour meter, at all. It just ends a pulse through the tach wire representing firing cycles.

    the Tach, if you order it (assuming Faria, but it doesn't matter either way) directly from the factory ~can~ be calibrated by them to read hours, making them match.. or.. you can hook an oscilloscope to it and send a slightly higher voltage to the meter than it is expecting- you may have to jump past the first capacitor to do so... the slightly higher voltage 'overdrives' the meter, logging more hours quicker... or.. you can send the proper voltage to it (safer, no need for surgery) and use the scopes timing feature...

    I thought about this long and hard when I installed my new tach/meter, and then said to myself "if I was to be in the market for a boat, I wouldn't look at the hour meter on the dash except to see if it had been replaced"... the PCM stores the number you will be most interested in seeing- and a whole lot more.. If I were to survey, that is the # that matters...

    my recommendation to you, for whatever value it has, is to service your boat completely in this offseason, install the new tach/meter, and amend your maintenance log book accordingly- it'll be easier to track starting fresh, and so long as you don't overshoot an interval, you'll never guess again about what time it is for what maintenance procedure..
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    SerenitySerenity Member Posts: 162 ✭✭✭

    I just replaced all my gauges as well. The new tachs will still read 0 hours. My dealer told me the hours are stored in the engine computers and he as a Mercruiser Certified dealer is also noting the hours. I also took a picture of the old tachs as well as have the old tachs still in my possession. There really is not anything else we can do that I know of.

    Good Luck with the new gauges. I had the Faria gauges and am excited to get out from under them.

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    BruceBruce Member Posts: 167 ✭✭
    Thanks very much, that really does answer my question. I just didn't want someone down the road thinking I was trying to turn back the hours.  But now knowing the actual time is stored in the pcm, I feel better and I will take a picture of the old tach before I remove it and will hang on to it for a future buyer (if I ever sell this boat, the wife and I love it)
      Thanks again for the quick responses and help
    2004 250 FV 
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    TikiHut2TikiHut2 Member Posts: 1,431 ✭✭✭✭✭
    edited January 2014
    I pitched my Faria tach last year and just replaced it with a $30 Teledyne tach that didn't have an hr gauge. There's no question that the engine computer has the most reliable info so I saw no need to keep the old tach (which was probably wrong anyway).

    Now I wish I could find a reasonably priced code reader to plug into the interface socket for my Merc 5.7
    2004 FV270, 300hp 5.7 350mag MPI Merc 305hrs, 2:20 Bravo3 OD w.22p props, 12v Lenco tabs, Kohler 5kw genset, A/C, etc.etc...
    Regular weekender, Trailer stored indoors, M/V TikiHut, Sarasota, Fl
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    Dream_InnDream_Inn Member, Moderator Posts: 7,589 mod

     

    RinkerYan said:
    I have no computer on my Yanmars. So I would keep the old ones.


    Geez, what good is diesel anyways! :P

    ....just another reason to have vesselview.  It gives you the hours right from the PCM.

    Dream 'Inn III -- 2008 400 Express

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    Black_DiamondBlack_Diamond Member Posts: 5,439 ✭✭✭✭✭
    I added hour meters where the OEM chart plotter was when my new tach was installed.  Just added a label under the meter to reference the hours to add to the meter so I don't forget when making notes on maintenance, etc.

    Past owner of a 2003 342FV
    PC BYC, Holland, MI
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    floater212floater212 Confirm Email, Member Posts: 121 ✭✭
    I had to change mine out twice... I just wrote the hours from the old tach onto the new one's back,so it would last. if some one asks I know the hours and then i'll tell them the story so they could check the back and add it to the hours seen on meter now, if they buy it when it's time to sell.
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    BruceBruce Member Posts: 167 ✭✭
    That's a great idea, I too will write the existing hours on the back of the new tach with a paint pen, thanks for the idea.   PS: my gauges are Teleflex. don't know if that's better or worse than Faria's??
    2004 250 FV 
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    BluescreenBluescreen Member Posts: 1
    edited January 2014
    I had the same situation, e.g. new tach with digital hour meter. My tach / hour meter is a Teleflex model 63474P.
    The hour meter has the hour glass symbol in the left hand side of the hour meter display. Simply applying power to the gauge would not clock hours without a pulse to the Sig. post of the gauge. What I found that will work (at least for the gauge model described) is a Sho-Me LED flasher Model

    SHO-ME LED FLASHER 11.1005.SF

    I connected my gauge to my power supply, along with the sho-me flasher (it's 12VDC as well). I then connected one of the led flash output wires to the sig wire of the tach. My hour glass symbol started to flash and my tach needle started to pulse between 0 and 200 RPM, some what of an erratic pattern on the hour glass symbol flash, so I momentarily touched the white wire of the show-me flasher to 12VDC (doing this cycles the led flashed output to different flash patterns). While changing the flash pattern I would watch the hour glass symbol on the tach and look for a stable cycle of the hour glass symbol, i.e. 1 second on, 1 second off, etc.. After changing the led flash cycle on the sho-me unit a couple of times I found a stable cycle. so far my new gauge has clocked to 0.9 since hooking it up this morning. As luck would have it, which is rare for me, I had one of the sho-me flashers in my parts bin so I didn't have to buy it for this project. However the sho-me unit can be found on the internet for ~$25 - $30. If getting your hours on your new tach / hour meter is important to you then what I described above should work for you if it's the standard tach / digital hour meter gauge that requires a pulse on the sig. connection of the tach to start the hour clock.

    The wiring hook-up is very straight forward.

    +12VDC to Ign of gauge and red wire of show-me flasher
    Ground to Gnd of gauge and black wire of sho-me flasher

    Use either led output wire of the show-me flasher (yellow or blue, makes no difference) it's a 2 channel unit and connect to the sig post of the tach..

    Momentarily touch the white wire of the show-me flasher to +12VDC to change the flash pattern if necessary.

    As always pay attention to your connections, no short circuits, etc. I used a variable voltage current limiting bench power supply, however you can using any 12VDC capable of supplying at least 250mA+. My current (Amps) display on my power supply is showing 90mA to 100mA with this rig hooked up @ 13.8VDC..If you use an unregulated power supply, e.g. a car battery, wall transformer, etc. make sure to wire an in line fuse with the positive lead of of the supply, I would use 250mA fuse max.

    Hope this helps.

    It appears to be a thorn in the side of several folks replacing this type of unit, talking about taking the gauge to a TV repair shop to have a square wave signal generator hooked up, coming back days later to pick it up and hope the hours are correct and so on.

    Disclaimer - I assume no responsibility for any damage that may occur as a result of following this advice. I have described my solution as accurately as possible, this may or may not work for your situation.

    Edit: I was looking at my power supply display with my bad eye. :-) The modified values listed above (mA) are the correct values not the originally posted 900ma / 1A values.

    Still clocking with no smoke @ 7 hours now.
    Post edited by Bluescreen on
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    212rowboat212rowboat Member Posts: 2,591 ✭✭✭✭✭
    Heckuva first post, man... Congrats, and thanks!!
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    BruceBruce Member Posts: 167 ✭✭
    Wow a lot of good info, thanks!
    2004 250 FV 
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    Dream_InnDream_Inn Member, Moderator Posts: 7,589 mod
    Welcome to the site Blue! Looks like your knowledge is already very helpful.

    Dream 'Inn III -- 2008 400 Express

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    BruceBruce Member Posts: 167 ✭✭
    Hey guys I need a little more help here if possible. I got the new tach installed and splashed the boat for the first time this year, this past weekend. Well the new tach is doing the exact same thing as the old one, it shows very erratic readings, and they change drastically when the tilt/trim switch is used??? I'm thinking probably a poor power or ground connection somewhere ( the connection on the back of the tach is clean and tight). Any suggestions on where to start looking next? Engine compartment or behind dash?? I'm hoping someone else has run across this type of problem before.
     Thanks in advance, Bruce
    2004 250 FV 
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