Grounding Prop Shaft

[Chris T]

A friend of mine suggested the following. To ground the prop shaft. connect a gound wire to the engine. Place the wire ever so slightly upon the top of the shaft to avoid scarring the shaft. Thus a grounded prop shaft. Anyone ever try this??
Regards,
Chris T

[HerbertFriedman]

grounding prop shaft

Not with a wire, but I was told by a power boater friend that a thin sheet of copper brushing against the shaft with tension provided by its "springiness" works OK. I do not see the problem as long as the contact is far away from the stuffing box. I thought of doing just that but my Tartan is 35 years old and I have no problem with electrolysis so I will leave well enough alone. I do hang a zinc over the side while at the dock connected to the ground system on my boat. It gets eaten up in about 6 months but extends my prop nut zinc quite a lot. Of course, the question is if the prop shaft is not grounded what good is the prop nut zinc?

[Chris T]

Not with a wire, but I was told by a power boater friend that a thin sheet of copper brushing against the shaft with tension provided by its "springiness" works OK. I do not see the problem as long as the contact is far away from the stuffing box. I thought of doing just that but my Tartan is 35 years old and I have no problem with electrolysis so I will leave well enough alone. I do hang a zinc over the side while at the dock connected to the ground system on my boat. It gets eaten up in about 6 months but extends my prop nut zinc quite a lot. Of course, the question is if the prop shaft is not grounded what good is the prop nut zinc?

Can you explain a little more as to why" the contact is far away from the stuffing box"? My stufffing box and prop shaft ( on the inside) is about 3 inches apart. Thanks Chris

[HerbertFriedman]

prop shaft grounding

I guess I never questioned how far from anything critical to put the sliding ground connection, just seems natural to get it away from something critical like the stuffing box. I have no idea how far is far enough.

[policecentral]

Ground the Shaft??

Perhaps I am missing something, but the shaft on my boat (and I suspect all others) is already grounded to the engine. The entire shaft passes through the stuffing box, directly to the engine and connected (grounded) via bolts into the transmission faceplate.

Fooling around with "external" grounding to a shaft that is already grounded is nonsense.

JSM

[rigspelt]

Perhaps I am missing something, but the shaft on my boat (and I suspect all others) is already grounded to the engine. The entire shaft passes through the stuffing box, directly to the engine and connected (grounded) via bolts into the transmission faceplate.

This makes sense to me, too. This old boat has no special prop shaft grounding or ground, and it was in excellent condition when I got it inspected recently after taking it out. Calder and Wing don't mention ground or grounding a prop shaft, far as I could tell.

[hanleyclifford]

grounding prop shaft

policecentral is right. if your shaft is bolted to the engine it IS grounded. the real question should be: will i get a benefit if i isolate the shaft from the engine? consider this: if the engine, shaft and prop are all mechanically and thus electrically connected in the presence of salt water (the electrolyte), a galvanic cell exists in which the engine is the least noble. hence it is imperative that the shaft zinc be kept current and effective. indeed is it possible that said zinc may be too distant to actually protect the engine from the adjacent ss shaft? food for thought - i am considering isolating my engine from trhe prop and shaft using a drivesaver or something similar. any thoughts on this? regarding the bonding and protection of thru hulls i would say only this: i regard the health of the wooden hull as much more important than the longevity of any thru hull. bonding creates a boat wide galvanic cell which causes electrons to flow between anode and cathode. this causes electromagnetic delignification of the wood and a buildup of that nasty white powder around thru hulls ( alkali anhydride) - caustic. far better to submerge your thru hulls in good oil paint and let them corrode at their own rate. write the date on new thru hulls and plan to replace them every 30 years or so

[ndutton]

Seemed like a good idea at the time

bonding creates a boat wide galvanic cell which causes electrons to flow between anode and cathode. this causes electromagnetic delignification of the wood and a buildup of that nasty white powder around thru hulls ( alkali anhydride) - caustic.

I didn't have any of the white alkali anhydride business until after I bonded all my bronze thru-hulls and stuffing box together. Needless to say the bond wire came out faster than it went in.

[baileyem]

I think that the only time you would have to worry about grounding your shaft would be if you had a 'drive-saver' type flexible coupling. The flexible coupleings are normally made of some non-metalic material and break the normal engine-shaft continuity.

Mike