Installing sending units in upgraded fuel tanks.

[Adeline]

I want to install sending units in my new Moeller 25 gallon polyethyline fuel tanks to serve my fuel gauge. I need to cut a 2 inch hole in them. A hole saw would seem like the way to go but I'm worried that instead of cutting, it may melt the material. I do'nt want to deform the S/U mating surface and risk leakage. Any suggestions?

[rogerbum]

[TyBoo]

I don't know if it is the same material as fuel tanks, but I recently relocated the filler spount on a molded freshwater tank. I used a thing called a HoleHawg, which is a fancy hole saw with carbide teeth. It cut thru quick and clean.

If you are using a hole saw, just cut for two seconds and bring it away from the material. Once your pilot is thru and there is a groove started for the hole, you should be able to keep it centered easily. The trick is to not let it get hot in the first place. It isn't the material getting hot so much as the tool getting hot and melting the chips of the material, which increases the friction and creates more heat. Once the hole is started, just push the saw down to touch, and lift it back up still running. If your hole saw is sharp, you'l probably be all the way through before it even has a chance to get warm.

[CAVU]

Adeline,
I would be a little concerned with the small chips falling into the tank? Do you think you will be able to rinse them all out? Or maybe vacuum them up through the small hole? A trick I use for hole saws in wood is to drill a small clearance hole that would touch the perimeter of the larger hole saw. This gives the chips a place to go while the saw is cutting. Unlike a drill bit the hole saw has no means of clearing the chips from the kerf which is why it heats up and burns the wood.

[starcrafttom]

try turning the tanks up side down and drill up. chips fall to the graounf not the tank. i assume that the new tanks are not in the boat yet.

[dogon dory]

Sorry, Folks - Post Deleted By Author

[Butch]

Guys, I have drilled hole in polyethylene many times and the tricks are make sure you use the right size hole saw, the saw be sharp, and the saw mandril have a pilot bit to keep the saw from "walking" when you first start. Most of all keep the RPM son the drill slow.

One word of advice... measure twice or more and cut only once

Butch

[rogerbum]

[Adeline]

Thanks for all the great replies, I'm more comfortable with the idea of using a hole saw now. However, I have another issue to address. The installation will require 5 small holes for the retaining screws. Moeller and Tempo tanks w/ senders have a metal retaining ring with threaded holes molded into them. My tanks lack this ring. Since I won't have access to the inside of the tank I won't be able to use washers and nuts. I'll either need to use self-tapping screws or some type of blind fastener such as a rivet or a rivet nut. http://www.rivetsplus.com/manufacture/avdel/dk_insert.asp Obviously, I want to ensure that fuel won't get by the fasteners or the sender. For liability reasons Tempo and Moeller don't endorse modifying their products. Opinions?

[Adeline]

Hi all, For those who desire to upgrade their fuel tanks and want to continue using their old fuel gauge I offer this http://www.wemausa.com/tank_se...s.htm . At the bottom of the page are c-shaped adapters. The Stainless Steel one is designed specifically for senderless tanks. Also, I think I'm going to use a different type(inductive) fuel sender http://shopping.rexmar.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=CENCGF-24&Category_Code=centroid . These units allow you to calibrate your gauge when empty and full. I hope someone will find this helpful. Pete

[Adeline]

Sorry, that first link didn't take. Try this one http://www.wemausa.com/tank_sensors/tank_level_sensors.htm .