Fuel gauge always reads full

[Jon W]

I replaced mine with a reed switch type sending unit from Catalina Direct. PN Z3529.

[Noah]

No one knows what tank you have except you! Lots of changes possible, often varying boat to boat. Take off the bulkhead and measure the height of tank. Or even better, remove the sender and measure it.

[Jon W]

Check the flange hole pattern on the tank as well.

[pbyrne]

No one knows what tank you have except you! Lots of changes possible, often varying boat to boat. Take off the bulkhead and measure the height of tank. Or even better, remove the sender and measure it.

True.  The boat is 2 hours away and I have to order it.  I've only got a limited time this weekend to fix it, so I'm willing to make an educated guess as to the size so I can work on it this weekend.

I found some photos that are not perfect, but they do show the size of the tank.  It seems to fill the space, and I think it's supposed to be 25 gallons.

[pbyrne]

I replaced mine with a reed switch type sending unit from Catalina Direct. PN Z3529.

Yeah.  That's the part from CD https://www.catalinadirect.com/shop-by-boat/catalina-36/engine/instruments/fuel-tank-sending-unit-12quot-stainless-c-34-c-36-25-gal-tank/ '

that I think is a direct match for this:  https://www.marineoutfitters.ca/index.cfm?category=10025|10273&product=75153522&code=739729000038

[pbyrne]

It's a lot of reading and information but do a search for "fuel gage".  Somewhere here is instructions for checking the fuel level sensor I think.  It's a float, lever and rheostat, very low teck.  Hardest part of checking it is emptying cockpit locker. Need a multimeter. Shamrocks was bad when I first got her, bought a generic one from local marine store, has worked for many years.
Honestly, I don't depend on the fuel gage much.  I use the hour meter.  Shamrock usually burns a little less than .7 gallons per hour.  Multiply .7 by hours since last fill up gives me the gallons to fill up.  Find your own burn rate by keeping a log of fuel use divided by engine hours. ie.  gallons per hour or g/h
Jim

On the topic of fuel consumption, when you say .7 gph, what RPM are you using?  The Universal Tech manual has double that at @2500 RPM.  Not arguing, just asking.  I realize I need to calc for my boat, but some rough guidelines are always helpful.

[Ron Hill]

pby : As mentioned measure the depth of your tank and if you use a "float" sender then get the deepest float sender for your tank.

A thought

[pbyrne]

pby : As mentioned measure the depth of your tank and if you use a "float" sender then get the deepest float sender for your tank.

A thought

Measured!

Tank is aluminum, 40" long and just a touch over 12" high.

I'm assuming the Moeller 12" unit I posted in here is the correct unit?

https://www.marineoutfitters.ca/index.cfm?category=10025|10273&product=75153522&code=739729000038

[Jon W]

Clicking on the link brings me to a list of engine related sub-categories.

[waughoo]

You'll likely have to copy and paste.  It appears that part of the link was not included in the "blue" hypertext.

[Ron Hill]

pby : Disregard my previous instructions!!!  Now that I've looked at the pictures of your fuel tank!!

Your fuel tank is different from the MK I C34 tanks which have a float switch access and the electrical connections on the TOP of the tank.  You may? need to pull the aft cabin Port side panel? and/or look thru the Beckson port and find where your wiring goes to the sender on your tank. Then you'll know what kind of sender to replace it with - IF you need a new sender??

Look in WiKi for the detailed Fuel gage trouble shooting procedures!!

Yes, .7 gal/hour is a good starting estimate. As you said you'll have to calculate it for your boat!!  I believe that RPM was about 2300-2500 rpm.

A few thoughts

[mark_53]

The parts you're talking about are pretty inexpensive.  Since a bad float mechanism seems most obvious, I'd get new float from CD or match it up on Amazon. If that doesn't work then try a new gauge.

[Jon W]

The CD unit is cheaper than Marine Outfitters as well. Is Ron saying your fuel sender doesn't mount on top of the tank?

[Ron Hill]

Guys : it's hard to tell what pby has got??  Maybe he's just posted the pictures on there side???   Hard to tell??  2 Beckson ports??

A thought

[pbyrne]

Apologies. https://www.marineoutfitters.ca/index.cfm?category=10025|10273&product=75153522&code=739729000038