Grounding thru-hull fittings

[ocuyler]

I'm installing new stainless steel thru-hull fittings for the new dual bilge pump set-up. Both are located well above the waterline. Both fittings, as seen in the image, have grounding screws. I grounded my new gas fill fitting, but didn't consider this.

Further, I installed a new bronze thru-hull to drain the forward fish well. It IS below the waterline. Any comments?

[paulfurnari]

The stainless thru-hull fittings on mine did not come with grounding screws and were not grounded. I have the original bronze thru-hull in the forward fish box. Still in good shape and has a bronze screw on cap on the interior which i don't think I've ever put on.- PF

[Finster]

The only thing I've seen grounded other than the fuel fill is a bronze grounding plate. I have never seen anoyone ground all threw hulls, as there's nothing to gain.

[ocuyler]

I guess if they were under water, electrolysis may be an issue. Thanks for the comments.

[abl1111]

I recently had the same question about grounding thru hulls, i.e. my bronze washdown and raw water intakes to prevent electrolysis and galvanic corrossion. Mercruiser's manual on this topic says clearly NOT to ground these things as they will become part of the system - They say it is better to keep them isolated.

[strick]

A while back someone over on Classic Mako threw a fit because one of the members did not have his thru hulls grounded. Mine is not grounded and I dont remember doing it to any of the boats I fished on in Alaska but thats not to say that it shouold not be done.....I guess it depends on how long your boat is kept in the water...if alot then I guess I'd do it.

strick

[Finster]

Grounding issues have always been a pain in the ass for boats (more so in saltwater) and I've seen some pretty freaky stuff. I saw a booger eater once replace the entire computer system and wiring harness due to a simple bad ground (on someone elses boat).
So I figure why complicate things that could potentilly drive you nuts down the road.

[RS]

I'm pretty sure it's not "grounding" per se, but rather bonding all underwater metals together with a zinc to protect against galvanic corrosion. Also, I read someting recently that said the metal fuel fill should NOT be bonded/grounded on boats that are trailered (fueled at gas stations) due to hazards from sparks.

[ocuyler]

Found this of interest:

USCG opinion on grounding/bonding fuel fill

My approach is now as follows: No grounding/bonding of the thru-hull fittings. Yes bonding/grounding of the stainless steel fill fitting (includes gas tank).

[SEAFARI]

The reason for star grounding all under water metals
is to create a common property between all the slight
variations in materials, doing so will minimize or
eliminate electrolysis, sort of like a signal ground
or electical "Ground Loop" problem between components.

Rodney