gauges bouncing

Discussion in 'Sport Cruisers' started by AFD, Aug 6, 2018.

  1. AFD

    AFD Active Member

    Jul 29, 2012
    Boston Harbor/Falmouth Ma
    1997 Sundancer 290 The fat beam version
    twins.
    Starboard 5.0 alpha 220HP
    Port 357 alpha 275hp
    4HP Yamaha for Dinghy
    I left the dock yesterday morning, boat packed with everything we own (it felt like), dinghy on the back, outboard in the cabin, cooler packed for the day, kids in pfd's, overnight stuff for the kids, and a plan for an actual fun day. we were going to travel about 45 miles and my mother was going to meet us and grab the kids for an overnight without kids for my wife and I. plan to party at the beach for the day then travel back 45 miles, dock and just relax. we got about 5 minutes in and a very minor bouncing in one gauge turned into all the gauges bouncing in sync except (ironically) the sync gauge.
    the volt meters were both reading the same between 8-10 volts (bouncing), in the cabin on the 12 volt panel it was reading about 12.5 volts, 14 volts when it was on the charger at the dock.
    I checked all the battery cables and they look fine and snug, no movement. all batteries were topped off 2 weeks ago but they were not very low at all they have also been on shore power the whole time except for when the boat is running or for a couple hours when we stopped for dinner.
    Nothing has changed in the boat in the past week, we went out last weekend for an evening with some friends and everything was fine when we got back.

    Now i assume that since all the gauges were bouncing that it is probably just a bad ground behind the gauge panel and that will be my first stop to look at tomorrow morning. i'm just looking for other suggestions. also, how do you check that your alternators are working without pulling them for testing?
    my boat day lasted about 12 minutes and we had to turn around and unload the boat, reload the truck and drive down to my mother's house to drop the kids off and we still had a great day out with a friend of mine but did miss out on one of the best boat days in the summer
     
  2. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    I think you're on the right track - at least a good first step - to check the ground bus bar behind your dash and each gauge's ground... might as well do all of them while you're there as it's quick and easy.

    Using a voltmeter, directly at the battery to begin with, measure volts with one engine running, then the other. You should see high 13's to low 14's. You could also use the alt's output post for a spot to measure.
     
  3. AFD

    AFD Active Member

    Jul 29, 2012
    Boston Harbor/Falmouth Ma
    1997 Sundancer 290 The fat beam version
    twins.
    Starboard 5.0 alpha 220HP
    Port 357 alpha 275hp
    4HP Yamaha for Dinghy
    will the alternators put out that voltage at idle?
     
  4. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    Maybe 13 and half-ish - but should be pretty close. Definitely higher than normal battery voltage of 12.5 to 12.8.
     
  5. AFD

    AFD Active Member

    Jul 29, 2012
    Boston Harbor/Falmouth Ma
    1997 Sundancer 290 The fat beam version
    twins.
    Starboard 5.0 alpha 220HP
    Port 357 alpha 275hp
    4HP Yamaha for Dinghy
    Ok, 14.6 on starboard alternator
    Nut on port alternator post was loose and must have been for awhile because the post was corroded and the motor is only 2 years old. Tightened and snapped. Removed nut at base and put the ring terminal on the base of post. Now reading 14.5 on port alternator.
    Think that explains the bouncing. All gauges are stable now.
    Problem still with low voltage at gauges though. Gauges showing 10volts at dash. Voltage drops to around 8 when revving above 1500rpms...more to come with pictures when I get home
     
  6. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    Dealing with corrosion... normal, but bad. Making progress... good. :)

    Does the voltage stay relatively stable at the alternator and/or batteries when you rev above 1500?

    Put your meter on the backside of the gauge. See if it reads the same as the gauge.
     
  7. AFD

    AFD Active Member

    Jul 29, 2012
    Boston Harbor/Falmouth Ma
    1997 Sundancer 290 The fat beam version
    twins.
    Starboard 5.0 alpha 220HP
    Port 357 alpha 275hp
    4HP Yamaha for Dinghy
    ok, i didn't get home until late, non boat issue.
    starboard alternator 14.6 volts
    port alternator was making 15.9-16.1 volts. this alternator is also showing some wobbling at the pulley so it may need to be replaced. its very minor and only noticeable while looking straight down on top of it. probably a bearing issue but its just out of warranty and only 2 years old.
    i wasn't able to measure the voltage while revving as i was alone and it was difficult to access the port alternator safely while the engine was running.

    The gauges which were reading about 10 volts at idle, and 9 volts while revving,
    measured at the back of the gauges i was getting

    Port gauge 11.4 idle and 10.1 revving
    Strbd gauge 10.9 idle and 9.6 revving

    measured at the batteries ( i was not able to measeure them all individually, safety and only having normal length arms)
    with engines running
    12.2 volts at the battery that has one starting and the house battery
    12.6 volts the other bank that is a dedicated starting battery
     
  8. ZZ13

    ZZ13 Well-Known Member GOLD Sponsor

    Nov 25, 2009
    Lady's Island, SC
    2001 400 Sedan Bridge
    Cummins 450 Diamond
    Power to the gauges goes through the engine start rocker switches (if your boat has rocker switches). I had similar low voltage gauge reading and after forever, finally found the connections on the back of the rocker switch were loose and one was actually installed wrong, with the male blade connector wedged between the female connector and the connector insulator rather than into the female connector.
     
    AFD likes this.
  9. AFD

    AFD Active Member

    Jul 29, 2012
    Boston Harbor/Falmouth Ma
    1997 Sundancer 290 The fat beam version
    twins.
    Starboard 5.0 alpha 220HP
    Port 357 alpha 275hp
    4HP Yamaha for Dinghy
    I took every wire off the back of every gauge, cleaned and put back and they were remarkably clean and still all tight but it still made a difference once reassembled as all the gauges are reading better ( had a starboard tach wandering issue and oil pressure gauge port side bounce on occasion that are completely gone). by better, i mean they don't wander at all but still low voltage on gauge. Also, I turned the 4cyl, 6cyl, 8cyl knob on the back of both tachs all the way back and forth and put them back on 8cy and that seems to have really smoothed out the wander of the starboard tach ( read that in another thread this week).

    as far as I can tell, it looks like the alternator output wire on the port engine was the cause of the entire gauge panel bouncing as it stopped as soon as i tightened the nut. I will monitor that alternator throughout the rest of the season and if it needs replacing i'll just do that. it will probably go anyway this winter once hauled.

    it looks now like the batteries are on their last legs but should hold out for the season. the starting batteries were bought last July from Advance auto because it was the closest place that had them on a saturday. The house is 4years old and an interstate. It looks like the starting ones only lasted the year. on AC power, they read 14 volts at the interior gauge but once off shore power, it drops to 12.6 on the panel and stays there. strange that the alternators don't keep the interior panel above 12.6 volts as they are putting out above 14 each
     
  10. AFD

    AFD Active Member

    Jul 29, 2012
    Boston Harbor/Falmouth Ma
    1997 Sundancer 290 The fat beam version
    twins.
    Starboard 5.0 alpha 220HP
    Port 357 alpha 275hp
    4HP Yamaha for Dinghy
    good to know, i'll check for corrosion there tomorrow morning when i get out of work. i didn't realize that the lead ran through the starting rockers first.
     
  11. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    16V is too high. Can kill a battery. Probably a bad voltage regulator in the alternator. However, sometimes a bad battery can cause weird issues, as well. I know this is a bit of work, but I would pull each battery and fully charge it, then get it load tested. If we're not starting off with good, clean power, then the rest is sometimes misleading. But that's good that you got some headway by cleaning/tightening connections.
     
  12. AFD

    AFD Active Member

    Jul 29, 2012
    Boston Harbor/Falmouth Ma
    1997 Sundancer 290 The fat beam version
    twins.
    Starboard 5.0 alpha 220HP
    Port 357 alpha 275hp
    4HP Yamaha for Dinghy

    that's what i was thinking. the boat has been sitting for extended periods of time as the weather is just unbearable for the wife and kids. we have only really run the engines for an hour or two here and there for short trips to a restaurant or just to go for a ride "to clean the bottom" in the later parts of summer, we tend to use the boat for longer trips when the humidity backs off and we can stand being on it for hours at a time. so wouldn't the battery charger take care of maintaining the batteries especially because they read 14 volts within seconds of activating the shore power? I understand the regulator would wreak havock on a battery but with such limited time on that alternator...would it be that bad? again, shouldn't the gauges be reading better especially if the alternator was putting out so much?
     
  13. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    The "14 volts within seconds of activating the shore power?"... What you're seeing on the gauges is what the battery charger is putting out, not the actual health of the batteries (that's what a load test will do).

    I'm not saying, for sure, that the regulator is bad - but things can go bad for no reason, sometimes - even relatively new items. But it's hard to fully/correctly diagnose things, especially 12V related things, if the battery is bad. I think fully checking out your batteries is the next step. There could still be another issue - another bad connection somewhere along the line to the gauge or corrosion in a wire or even a belt slipping - but tackle one thing at a time. Autozone (or similar) can load test batteries.

    One other quick thing is to check that the alternator is grounded properly/well (again, checking out the basics before proceeding). You can do this by grounding the alternator with a separate, heavy, wire (battery jumper cables can work if you can fit them in) directly to the engine - a bolt/nut/whatever - even the bolts at the top of the manifold risers. You can also ground directly to the alt's case.
     
  14. AFD

    AFD Active Member

    Jul 29, 2012
    Boston Harbor/Falmouth Ma
    1997 Sundancer 290 The fat beam version
    twins.
    Starboard 5.0 alpha 220HP
    Port 357 alpha 275hp
    4HP Yamaha for Dinghy
    i know that i'm seeing what the charger is putting out, what i don't understand is that if the charger is putting out 14 volts and i see that on the gauge...why am i not seeing that when the engines are running if my alternators are putting out 14.6 and 15.9 respectively?

    I actually did check this first and grounded to the bolts of the manifold risers while i was testing them with the voltmeter
     
  15. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    Correct me if I'm wrong, but you weren't yet able to check voltage AT the batteries, right? Let's get that done, first, before trying to guess... what makes the most logical sense is simply a corrosion/wiring issue from the alternator to the battery, or the connection at the battery. If it's X-volts at one end, but not the other...

    Hook up your meter, put it in a good spot, route the wires so they don't get caught in the belt, then go and start the engine. Use longer leads/extra wire if needed.
     
  16. AFD

    AFD Active Member

    Jul 29, 2012
    Boston Harbor/Falmouth Ma
    1997 Sundancer 290 The fat beam version
    twins.
    Starboard 5.0 alpha 220HP
    Port 357 alpha 275hp
    4HP Yamaha for Dinghy
    correct, i was not able to get to all the batteries with the engines running, specifically the port/newer engine which is the one with the 15.9+ volts coming from the alternator. It was also very hot and humid and i was alone and slightly frustrated, and ran out of time. I will be back on the boat on friday so i can spend some more time with it then.

    What i meant was the gauge on the interior 12 volt panel (not the dash gauges) goes directly to 14volts on the 120volt ac charger. when the engines are running it reads 12.6 volts on the same gauge.
     
  17. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    Hot, humid, alone, frustrated, no time... Yeah, I understand that!

    We'll know more once you check at the batteries. But... 12.6V is right in line with what a battery would read just sitting there. The boats I have personally owned never had a cabin 12V gauge, so I'm just taking a stab here, but... Isn't there some kind of selector switch for the cabin gauge to select which bank of batteries it shows? And... it may default to house battery/ies? There may also be some correlation with what position/s you have your main battery selector switch on, as well. Again, though, this is just a guess.
     
  18. AFD

    AFD Active Member

    Jul 29, 2012
    Boston Harbor/Falmouth Ma
    1997 Sundancer 290 The fat beam version
    twins.
    Starboard 5.0 alpha 220HP
    Port 357 alpha 275hp
    4HP Yamaha for Dinghy
    I have 2 individual battery switches but they remain on all year. I'm on shore power and sometimes just pop down to the boat for whatever. So the switches are always on. The only circuits that remain on at the 12 volt panel are the cabin lighting and stereo but the switches for lights are off and the stereo has power but gets turned off. Its left with power so the stereo doesn't take 3 minutes to load up (it's an old Sony and its annoying).
    The problem with the 12.6 reading is that was while the engines are running and should be in the 13.5-14v area if memory serves me, which it usually doesnt.
     
  19. AFD

    AFD Active Member

    Jul 29, 2012
    Boston Harbor/Falmouth Ma
    1997 Sundancer 290 The fat beam version
    twins.
    Starboard 5.0 alpha 220HP
    Port 357 alpha 275hp
    4HP Yamaha for Dinghy
    ok, must have just been the alternator wiring and some dirty contacts behind the gauages. all reading normal now after a good charge on the shore power and a good 1 hour run yesterday and an hour back.
     

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