Sundancer370On my 1995 Sundancer...

[kimo]

Sundancer370

On my 1995 Sundancer the Fuel & Tach gauges are unreliable.

Fuel gauges; Always show low fuel level & show different to each other even when I know physically that Iv'e just filled both tanks.  

Can anyone advise a simple way to determine if its the Tank Sending units or the gauges which are at fault, I took out the Stb'd sender and its just a cork float on a rod with the sensor unit on the top connecting to the tank closing plate. I clamped it to to the side of my workshop water tub and filled the tub, the rod lifted with the rising water so that doesn't seem to be the problem but I'm not sure if the sensor is working properly because it doesn't make any kind of noise or clicking to indicate it is sensing the rising or lowering water level.

Ref the gauges themselves, I removed the dash bezel cover to expose all the gauges backsides then disconnected "all" gauges wiring one by one and cleaned all connections best as I could with a small wire brush and emery cloth etc and reconnected them again.                      All gauges appear in good order physically and visually etc but am not sure about actual performance, I am suspecting that it is the gauges at fault (possibly just the age factor) as the sending unit is a simple cork float on a rod but need to know how to test one against the other to find if its the sender sensor or the gauges themselves. Iv'e read on different sites that Searay gauges are notorious for being inaccurate.

Tachometers; Similar as above for Tach's, they never show same rpm when both engines equalized on center paralleling guage so difficult to know which one is correct or even if one of them is correct that is. Big discrepancy in rpm's showing btw'n port & stb'd guages and stb'd gauge flicks around heavily when gauge bezel is tapped.  

Ref both above, if these gauges were even reasonably close to each other I wouldn't be too concerned "especially the fuel gauges" but there is a wide discrepancy between them which doesn't give a good comfort feeling when one is showing almost empty and one is showing just a third full !!  when I was sure I had more gas than that out in middle of Lake Ontario with still about 5hrs to go to get home.

I'm sure these situations have been experienced by many boaters so am hopeful to receive comments to determine how to test whether its gauges or sending units at fault to be able to source the correct replacement items. 

Cheers;

[wingless]

Welcome to the forum.

There are many sites showing how to test the gauges. Here is one.

https://www.stewartwarnercanada.com/media/pdf/install_instructions/Service%20instructions%20for%20electrical%20gauges.PDF

[kimo]

Many thanks for the heads up on this site, will study it and then try to see what I can determine.

Rgd’s; John.

[Shark]

My tach's on my 1989 34 sea ray and 1992 400 express would do the same. One would read more so I would tap them and then they would be okay for a while and then do it again. There is an adjustment on the back of the tachs that sea ray told me about. You would turn the setting knob from 4 cly. to 6 cyl. and then to 8 cly. and they would be okay for awhile. The best bet is to buy better tachs!. My gas gauges on all my boats would always show less then what I would have in the tank.

[kimo]

Thanks Shark; Will check for that adjustment on the back of Tach's and see what its about but won't adjust anything until boat is back in water springtime so can see any immediate result. I'm leaning towards getting new fuel & tach gauges, what kind did you buy were they direct Searay replacements or other brand.

Rgd's John.

[Fat_Cat]

See if the float works in your fuel. I assume you have gas. I had senders that would read empty on one side and slow to show full on the other. They would float perfectly when tested in water but sink like a stone when I observed them in the tank looking through the top of the tank where they are bolted to the tank. I bought KUS units on eBay and they now work properly.

[zozzimus]

An airline pilot friend once told me "the only time to trust s fuel gauge is when it's showing empty" They are not very reliable the float in the tank can get full of fuel and give weird readings or the gauge can be defective, but your mechanic should be able to replace it, as for the tach it could be the sender or the gauge, borrow a tachometer and try it first!

[zozzimus]

You could switch the tach gauge port to stbd see if either on is defective if the same gauge is acting up that will eliminate one gauge problem!

[BigTuna]

I don’t think that you should be spending a lot of time trying to troubleshoot. The cost of the sending unit is anywhere between 28.00-$51.00. I would replace both and and if you are still getting a wrong indication, then move to the instrument.

[Alumofcu]

Sending units are easy to test

[kimo]

Thanks all you guys for all the great comments/advice rec'd to date, much appct'd. Will be following up on all options to resolve the situations I have. Cheers; John.