Gas Gage question.. 215 explorer

[MTBfish]

So short version, since i'm at work and I just spent 20 min on the long version and it never posted.
2002, 215 explorer, 200 Yamaha

Gas gage shows empty all the time.   Thought it was empty, so added 25 gall (100 gall tank), still shows empty.  

How can I test the sending unit?

How easy is it to replace using the existing TINY access hole?

Is the sending unit a standard replacement?  Avaialblility and expected cost?

Bob, need your help/experirnce... anyone else as well.   When i bought the project it showed empty and still does...

Thanks

[seabob4]

Boy, I tell ya, this is the year of sending units!  You've got the Yam digital gauges with the fuel gauge in the face of the tach.  Works the same way as a normal dial gauge, on resistance.  First check, take the ground off the sender and touch it on the sending wire (pink).  It should peg the gauge to full (all bars).  If not, then check for continuity between the ground and a "known" good ground, and also check for continuity between the sending wire at the sender and the sending wire under the helm (white, I believe).  Report back your findings...

[MTBfish]

Thanks Bob, so here is what i found.  Went to take a better look at the sending unit (i'm guessing that is what it is) the round thing with the wires.  The pink wire to the middle is on still, the black wire was there, but looks like the only thing keeping it in place was rust.  As soon as I touched it it broke off.  BTW the sending uniit looks like a coffee filter full of used coffee by the amount of rust on the thing.  It appears to also be separating in layers like flaking apart.  I did try grounding the unit, since I had the black wire loose I touched the center peg.   Nothing on the gage.   Didn't take it any further based on frustration and realization I have no way to fix unless I remove the rusted to hell sending unit.  
It seems like no good way to get the sending unit out, of the 5 screws holding it in place, only one seems to be accessble with a screwdriver...
Any suggestions would be appreciated.

[seabob4]

Thanks Bob, so here is what i found.  Went to take a better look at the sending unit (i'm guessing that is what it is) the round thing with the wires.  The pink wire to the middle is on still, the black wire was there, but looks like the only thing keeping it in place was rust.  As soon as I touched it it broke off.  BTW the sending uniit looks like a coffee filter full of used coffee by the amount of rust on the thing.  It appears to also be separating in layers like flaking apart.  I did try grounding the unit, since I had the black wire loose I touched the center peg.   Nothing on the gage.   Didn't take it any further based on frustration and realization I have no way to fix unless I remove the rusted to hell sending unit.  
It seems like no good way to get the sending unit out, of the 5 screws holding it in place, only one seems to be accessble with a screwdriver...
Any suggestions would be appreciated.

You'd swear the hull prep guys would have centered the tank do the sender was under the pie! :x  :x

Anyway, those screws should have 5/16" heads on them, short 5/16" socket or a 5/16" conbination wrench will get them out.  Spray with penetrant before trying to remove, as with all that rust, the heads will have a tendency to break off, and then you are SOL.  Once you get the sender base loose, lift it up a little, and you'll be able to tilt it towards the pie opening to get it out.  Verify that the ground is good, but from what you describe, I'd say the sender is shot...

[MTBfish]

Thanks Bob... guess no one asked you where to put the pie hole???  
So, from what I remember, the screws are Philips heads, I'm not that technically versed, but is 5/16 a ref to a socket that would fit the screw would the screw be a hex nut instaed od Phillips?  or is the a 5/16 phillips head ref?   Anyway, I'll work at removing the sending unit see how much I can get out or destroy...  Whats my chances of getting all that rust down the tank and making a mess of my 20+ gall of gas?  I'll try to blow away all the loose rust, but think it will be messies getting it out.  

I had a great idea, how about a hole right where the pie hole is and silicone a piece of glass there...  it will be my "visual" gage

[seabob4]

Thanks Bob... guess no one asked you where to put the pie hole???  
So, from what I remember, the screws are Philips heads, I'm not that technically versed, but is 5/16 a ref to a socket that would fit the screw would the screw be a hex nut instaed od Phillips?  or is the a 5/16 phillips head ref?   Anyway, I'll work at removing the sending unit see how much I can get out or destroy...  Whats my chances of getting all that rust down the tank and making a mess of my 20+ gall of gas?  I'll try to blow away all the loose rust, but think it will be messies getting it out.  

I had a great idea, how about a hole right where the pie hole is and silicone a piece of glass there...  it will be my "visual" gage

Sorry, some tank builders use hex head mounting screws, some Phillips head Pan-head type screws.  Try this.  Take a short phillips head bit like you find in the body of a "multi-purpose" screwdriver, and put it in a pair of vise-grips.  I know, it's a PITA, but it is ONE way to skin a cat...

[MTBfish]

SUCCESS!!, the sending unit is out.  looks like a 13" sweep from full to empty.  I saw some similar set up in the marine shop yesterday, will see if it matches so I can get a new one in ASAP, instead of having to internet one over...  I will also look for som hex screws instead of Phillips, so the next guy wont go thru this head ache.  I also tested the wireing and its slow but when I connect he 2 wires together after aboout 30 sec or so the gage reaches a full tank.   Is it normal for a slow creep from emprt to full, I would expect electronics to go from 0 to full in a snap.  Also guess I got luckie, its only the sending unit and not wireing or the gage, all that sounds expensive and time consuming tracing those lines aroound.
Any special consideration while installing the new SU?   Looks traight forward.

On a different note, What is up with those courtesy lights?   Seems like you dismantle the boat to replace a $2 bulb when the light goes out.   I'm sure someone has come up with a better solution so you can access and replace the bulbs from the outside....I hope so.   Anyway, any insight on that aspect would help.

Bob as always, your advise and help is appreciated, Thank You.

[cdoyal]

Also guess I got luckie, its only the sending unit and not wireing or the gage, all that sounds expensive and time consuming tracing those lines aroound.

A good ground cures a ton of problems. Don't be afraid to replace any that look dicey. You'll be glad you did. Also, everyone on the forum will tell you to use a good heat shrink connector.

[seabob4]

With a "normal" fuel gauge, the needle will swing instantly to full when you touch the ground to the sending wire.  But I think the gauge in the Yam tach takes a little while to register.

[MTBfish]

Final update... New unit in and sending correctly, so instead  of a empty tank I had 3/4 of a tank, according to the new unit.  But at least its reading something, even if it is not 100 accurate, I have a ref point.     The new unit did come with HEX sccrews, just in case I need to do this againg in 10 years,, (yeah right).  Anyone know what the black rubberie stuff all over the conenctions are, and where do you get it?.. seems like a little insurance for keeping the connections cleaner/longer...

Thanks all!

[seabob4]

Liquid neoprene, sometimes called "Liquid Electrical Tape".  You can get it at HD...