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watson524

Fuel gauge gone whacky and RPM surge/fall

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I'm not even sure where to start with this one.... Boat's been running great for the first 20 hours. Took it in, dealer did the 20 hour service, drove it back from marina 6/29 (about 11 miles down lake), picked up some friends went out for the nite, no issues at all. 7/7 went out to see the fireworks. No issues on the ride out (sans the nuts on jet skis). Coming back down the lake about midnite, things went wacky.

Before we left the dock on 7/7 the analog gas/trim/water gauge read 3/4 on the fuel. The smartcraft gauge read 60.4 gallons so those were in sync. 

Coming back, I had the tabs down because I was only going about 15mph due to it being dark and being on full alert with people coming in from fireworks. I noticed that rpm would suddenly start dropping as well as speed without touching the throttle. No odd engine noises at all, no alarms. I'd tap the throttle a bit, it would stay stead for a brief period, then start accelerating. Did this repeatedly but again, no odd noises or alarms or anything. I sort of wonder if it was just coming on and off plane that was "causing" all this and plan to take it out tomorrow or Wednesday and see what's what. Had no issues at idle speed while docking.

During all this, I happened to notice the analog trim/water/fuel gauge flicker. First I thought it was my eyes, then saw it again. This is when I noticed that the fuel gauge was at 7/8. Hey, check that out, my boat makes its own gas!! WTF?? So I flipped the smartcraft gauge from RPM to fuel (which reminds me I need to turn off a few screens I just don't need) and it was reading 70.8 gallons. And while that's in sync with the analog gauge obviously, boats don't make gas. The guage flickered probably 5 or 6 more times. When I got into the no wake zone, the digital and analog gauges started reading the right amount of fuel (in the 50+ gallon range, which would make sense since we left the dock with 60'ish). I know that the tank sensor, at least on my old boat, would be affected by bow rise but it never went HIGHER with the bow in the air. And even if it was an issue with the plane of the boat affecting the reading, it doesn't explain the flickering on the analog gauge.

Anyone want to take a stab at this? Like I said, I'm going to take it out this week and see what's what, especially on the RPM side. I may not be out late enough with enough dark to really see a gauge flicker but we'll see.

thanks!

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There is a plug set atop your engine that feed the helm and smart craft. This link needs to be broken in order to connect a service scan tool and I just had one here where the tech did not plug the harness back together all the way when he returned the boat to my friend. He had a warranty issue they fixed, but I cannot think of any reason for your dealer to use a scan tool for a standard 20 hour service. The reason I mention this is he had your same symptoms and I found the issue by accident as the plug is under the plastic engine cover. Pure luck. I do believe that you have a loose connection somewhere so I'd start atop the engine and work my way forward, but in your case she needs to revisit the dealer as it's warranty in any case. W

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Thanks Wingnut. Since there were no alarms, I can't imagine they'd scan preemptively but I suppose you never know. I'll try to get over there tonite to take a loo and see what's what. I'm honestly more concerned about the RPM surge/drop but hopefully that really was just a planing issue. Just couldn't believe how pronounced it was. Should have smoother water today now that the weekenders are gone home.

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1 hour ago, watson524 said:

Thanks Wingnut. Since there were no alarms, I can't imagine they'd scan preemptively but I suppose you never know. I'll try to get over there tonite to take a loo and see what's what. I'm honestly more concerned about the RPM surge/drop but hopefully that really was just a planing issue. Just couldn't believe how pronounced it was. Should have smoother water today now that the weekenders are gone home.

All speculation at this point but maybe he disturbed the top engine harness when he stretched back to grease the engine coupler. Several plugs in that mess both in the engine bay and at the helm station.  W

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1 hour ago, Wingnut said:

All speculation at this point but maybe he disturbed the top engine harness when he stretched back to grease the engine coupler. Several plugs in that mess both in the engine bay and at the helm station.  W

I can't even imagine the contortions they have to do just to get in the back there. I was screwing around with the floor drain valve on starboard side and almost fell in the engine bay

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1 hour ago, watson524 said:

I can't even imagine the contortions they have to do just to get in the back there. I was screwing around with the floor drain valve on starboard side and almost fell in the engine bay

Engine hatch needs to be lifted to 90 degrees or beyond. Opens up a whole new world. W

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28 minutes ago, Wingnut said:

Engine hatch needs to be lifted to 90 degrees or beyond. Opens up a whole new world. W

Well that seems like cheating LOL! Hopefully the storms hold up for this evening and I can get over there.

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Couldn't get to the boat until tonite given the nasty storms that rolled through last nite.... Anyway, checked all the plugs I could see in the engine bay before flipping the battery on. Read the gauges and the smartcraft was reading fuel as it should, within a tenth of what it was when we docked and logged it last. The analog gauge matched. Went out for a ride and experienced no weird RPM behavior and other than the expect fuel level changes on both gauges when not on plane vs up on plane, no weird gauge issues either. A little too bright out to notice any dimming/flashing of the gauge but readings were definitely right.

Thinking the RPM issue really was just when I was plowing the water vs being up on plane and the throttle is really sensitive but I was able to hold 25mph +/- 1mph and 40 rpm for a long stretch twice so.....

I guess I'll just have to keep an eye on things and see if it repeats. We may be out again tomorrow, if not definitely Sunday so I'll report back if I find anything else out.

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9 hours ago, watson524 said:

Couldn't get to the boat until tonite given the nasty storms that rolled through last nite.... Anyway, checked all the plugs I could see in the engine bay before flipping the battery on. Read the gauges and the smartcraft was reading fuel as it should, within a tenth of what it was when we docked and logged it last. The analog gauge matched. Went out for a ride and experienced no weird RPM behavior and other than the expect fuel level changes on both gauges when not on plane vs up on plane, no weird gauge issues either. A little too bright out to notice any dimming/flashing of the gauge but readings were definitely right.

Thinking the RPM issue really was just when I was plowing the water vs being up on plane and the throttle is really sensitive but I was able to hold 25mph +/- 1mph and 40 rpm for a long stretch twice so.....

I guess I'll just have to keep an eye on things and see if it repeats. We may be out again tomorrow, if not definitely Sunday so I'll report back if I find anything else out.

Is there any chance you were running with low battery voltage during your problem outing?  W

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12 minutes ago, Wingnut said:

Is there any chance you were running with low battery voltage during your problem outing?  W

Nope, not that I know of. I always do a full scroll through of the gauge (which is why I was again reminded I need to update and stop showing some like the break in hours) before I start and then periodically again while underway (call me paranoid, I prefer "thorough" LOL). 

On start, I always get the low battery warning on the garmin because of the quick draw (down to 10.8 - 11.2), no trouble starting and then as we go along it gets back up to 14.2'ish.

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4 minutes ago, watson524 said:

Nope, not that I know of. I always do a full scroll through of the gauge (which is why I was again reminded I need to update and stop showing some like the break in hours) before I start and then periodically again while underway (call me paranoid, I prefer "thorough" LOL). 

On start, I always get the low battery warning on the garmin because of the quick draw (down to 10.8 - 11.2), no trouble starting and then as we go along it gets back up to 14.2'ish.

Intermittent electrical gremlins are the worse.  Saw a soccer mom on the news pull her mini-van away with the gas pump still connected, and she set the fuel island and two Lamborghini's ablaze so I guess it can usually get worse. Hello State Farm.  

 

http://www.dailymail.co.uk/video/news/video-1724676/Video-400K-Lamborghini-torched-minivan-pulls-gas-pump.html

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That's what I'm afraid of. For now, I'm just going to have to keep an eye on it. Even tho we weren't out at dusk last nite, I put the nav and cockpit lights on trying to replicate exact conditions from that nite.

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