Re-rigging questions

DonMacN · 23 March 2009, 22:43

folks,

Re-rigging the boat over the last few weeks and two questions now arise:

1) about to re-install the battery cut out switch. It's a 'back to square one' job, and it occurs to me to ask if it matters which circuit the switch is wired to?

I did it to earth/negative first time round, kind of following a 'negative earth' car-based approach, but does it matter in a boat when the battery isn't earthed to the chassis/bodywork??

2) Going to fit a new 'inspection cover' to the fuel tank. THe replacement came with an 'o' ring to seal it to the tank - the original had a cork gasket. Given that there might be fuel right up into the external filler pipe ( ie up past the level of the inspection cover) I wonder just how effective the o ring will be and wonder if there's anything else I could use to help ensure a good seal. I'd hate to have to lift the console if I found a fuel leak at that stage. Someone's suggested a loctite type seal, but all the ones I can see say 'not recommended for plastic parts'. Is this just them covering their backs? Do they work with plastic? I have some Loctite 276 (or something like that? 576?) which I used to seal the threads on the hydraulic steering. Would be useful if I could use that up. Any suggestions?

THanks!

Tim M · 24 March 2009, 00:25

Connect the isolator to the positive side.

jyasaki · 24 March 2009, 16:24

I would assume that if the O-ring is intended for a fuel tank cover, that it is fuel-resistant. Use something like Rector Seal (gas compatible thread sealant) if you're worried about it.

Most electrical systems use the negative side as a common, and switch the positive side. No particular reason on boats, as far as I know, just common practice. As you said, there is no "ground" per se, as there is on cars (where the cathode is tied to the chassis), so you could, in essence, switch anywhere along the circuit.

That may, however, cause problems later when someone else tries to assist you with electrical problem resolution. Better to stick with convention, IMO.

jky

martini · 24 March 2009, 17:10

There could be a few small areas of common ground on the negative side, ie negative busbars, banks of switches with a common ground point etc., these are often much less insulated than positive areas so I would suggest fitting the isolator on the positive side to help prevent any shorting out inside the console.

Theres a gasket sealer called Hermetite Red which is petrol resistant, I used it on my inspection covers which also had a cork gasket and I used it on all the threaded pipe fittings, no problems so far. Its quite widely available in motor factors etc.

DonMacN · 24 March 2009, 18:21

thanks all!

Switching the positive side makes life just a little easier because of the battery configuration, so that's good news!

ref the 'O' ring, I'm sure it's fuel compatible, what I didn't mention above (oops) was that I'm a little concerned about using it alone because the top of the tank has deformed - only very slightly, and I'm sure the cover fixing screws will pull most of that out - but enough that I just think a 'belt and braces' approach would be useful.

I'd seen hermetite red at a local parts shop but the guys there weren't entirely sure it would do the job, so it's good to know that it's been used for this type of thing with no problem.

Cheers!