Cutting a sender hole in my water tank?

[bugbitten]

I just got one of those fancy-schmanzy Blue Sea gauges that measures battery state, bilge operations, AND tank levels. I really want it to monitor the water tank in my 9.2A, but need to cut a 1.5" hole in the top of the tank for the sender. The only requirement is that it be more than three inches from a side or corner. It's pretty low profile, so it'll fit under the v-berth cushions okay.

Am I even more foolhardy than usual in thinking about cutting a sizable hole in a leak-free tank? It takes the standard, SAE 5 Bolt opening, using #10 pan head screws. I'm a bit worried about getting it down tightly enough - given the relative thinness of the fiberglass - that sloshing won't lead to some leakage around the gasket. Guess I could try it as is, then add some reinforcement if it's not pulling down sufficiently.

John

 

[BobM]

Bug...

...use butyl tape instead of the gasket ;-)

You have a fg tank? Mine is aluminum.

 

[Nom De Guerre]

...use butyl tape instead of the gasket ;-)

You have a fg tank? Mine is aluminum.

I think I would choose a gasket (such as EPDM) over butyl tape for a potable water application such as a fresh water tank.

 

[bugbitten]

I am a big butyl tape fan, I have to say. Maybe they make a food grade version!

 

[bugbitten]

...use butyl tape instead of the gasket ;-)

You have a fg tank? Mine is aluminum.

Well, when I pulled off the plywood cover that's under the v-berth cushions, there is just more painted surface that looks like much of the rest of the boat. It's fairly flexible if you push on it. I'm assuming it's fiberglass, but I guess it could be painted aluminum. I'll try scratching the surface and see what I get.

 

[BobM]

There was a cover under my vee berth over a shallow storage area. It was clearly a sheet of gray plywood tabbed together with fiberglass woven tape and painted gray. I used a vibratory saw to cut the bottom off. I think I posted some photos.

 

[BobM]

Here is what it looked like after surgery. I am still not done. Be careful...the sawzall got away from me and I poked a tiny hole thru my hull. Above the waterline thankfully and I wasn't in the water.

 

[bugbitten]

Thanks, Bob. I went back and looked at it (after actually clearing all junk out of the v-berth) and realized it was a plywood cover over aluminum. I'm thinking I'll try to gingerly cut a 3" hole out of the plywood and then cut the 1 5/8ths inch hole for the sender using the same center point.

I probably have a similar collection of Ryobi 18V tools. My batteries seem to be giving up the ghost at an alarming rate these days.

John

 

[BobM]

Mine too. But I left the lithium ones out last winter in the garage which I knew was bad for them. Batteries plus can rebuild the NiCad ones but not the lithium ones.

 

[bugbitten]

Well, the deed is done. I cut a 3" hole out of the plywood first, then the 1 5/8ths inch one out of the aluminum for the sender. I kept vacuuming chips up as I went, so I'm hoping nothing catastrophic got into the tank. (I do have a sizable filter in the system, but it's downstream of the pump.) The Blue Sea instructions said to try to center it on the tank. It ended up being very close to the 3" minimum distance from a baffle, so, were I to do it again, I'd move the hole a couple of inches forward. I'll try to get it wired up in the next day or two and let you know how it works. There might be good winds for a test sail of the gasket this afternoon, but I think the admiral has other plans.

John

 

[bugbitten]

Success, I think. The gauge reads full on tank 1, which is the water tank. Unfortunately, it also reads full on tank 2, which doesn't exist. I'll use some of the water on tank 1 and see if the reading drops.

I'm a teeny bit disappointed with the gauge itself. It appears you can either have a third battery bank reading OR a bilge pump monitor. I was hoping to have both. Maybe I can convince one of the unnecessary tank monitors to take on a different task. Still, it multi-tasks more than any other gauge I've come across, AND I think it'll neatly replace the original analog voltmeter in the electrical panel w/o any major mods.

Off to read the rather lengthy manual.

I'll update this once it's properly mounted in the nav station area and I actually see some movement on tank #1.

John

 

[bugbitten]

Mine too. But I left the lithium ones out last winter in the garage which I knew was bad for them. Batteries plus can rebuild the NiCad ones but not the lithium ones.

I didn't know about Battery Plus rebuilding the Ryobi NiCads. I'll have to check that out. Seems like I ought to be able to cannibalize one to repair a couple of others, assuming it's a bad cell that's the issue.

 

[bugbitten]

Here's the new meter shoved a bit crookedly into the old meter's cut out. The opening is just a tiny bit small. I'm going to try to enlarge it a bit toward the battery switch side, as there is actually a bit more clearance on that side, and that would relieve some of the crowding on the cabin lights breaker.

I'm thinking about replacing the current, momentary toggle below the meter with an standard, on-off-on one so I can switch between monitoring battery banks two and three and still keep the bilge pump monitor going (with this meter, you normally can either monitor two banks and the bilge or three banks).

It's going to be a tight fit, but I think it'll work just fine. I can't say it looks OEM, but I'm hoping it won't shout "kludge" either, once it's done.

John