I would like to tap a barbed fitting into the aluminum gearcase of my
outboard motor. I cannot find stainless barbed fittings and I assume brass
and aluminum touching under salt water is a no- no. If I tap the aluminum to
take a stainless 1/4" bushing and then thread in a 1/8" barbed brass fitting
will there still be corrosion problems. There are several zinc anodes on the
motor and aluminum hull.

mark wrote:
I would like to tap a barbed fitting into the aluminum gearcase of my
outboard motor. I cannot find stainless barbed fittings and I assume
brass and aluminum touching under salt water is a no- no. If I tap
the aluminum to take a stainless 1/4" bushing and then thread in a
1/8" barbed brass fitting will there still be corrosion problems.
There are several zinc anodes on the motor and aluminum hull.


Umm - first question - why?
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In article ,
says...
I would like to tap a barbed fitting into the aluminum gearcase of my
outboard motor. I cannot find stainless barbed fittings and I assume brass
and aluminum touching under salt water is a no- no. If I tap the aluminum to
take a stainless 1/4" bushing and then thread in a 1/8" barbed brass fitting
will there still be corrosion problems. There are several zinc anodes on the
motor and aluminum hull.


You're correct that brass will be worse than stainless, but SS barbs are
available. See McMaster pp.240 & 245 for examples. A tough plastic would
be safest from corrosion - McM has a lot of plastic barbs and
compression fittings as well.

Ned Simmons

On Wed, 05 Apr 2006 18:20:32 GMT, "mark"
wrote:

I would like to tap a barbed fitting into the aluminum gearcase of my
outboard motor. I cannot find stainless barbed fittings and I assume brass
and aluminum touching under salt water is a no- no. If I tap the aluminum to
take a stainless 1/4" bushing and then thread in a 1/8" barbed brass fitting
will there still be corrosion problems. There are several zinc anodes on the
motor and aluminum hull.

Stainless and aluminum are also not good together. The zinc anodes
won't help much if they're very far from the joint because the local
return path for current is much shorter (hence lower resistance) than
the path from the Zn anode.

A strong plastic fitting would be best. It would be best to make
your own, using a relatively small thru-hole to get plenty of wall
thickness. That could be a bushing or adaptor; then the barb (more
moment on long barb) could be made of brass.

I would make an aluminum barbed fitting and then hard- anodize it.
Anodizing will keep the threads from galling, and presents an
electrically non-conductive surface. Probably more screwing around
than you want to do.

I have fitted a brass barbed fitting to my outboard's leg. It is higher
up though, where the exhaust relief port is located. My outboard is in
a semi closed well and this port would fill the well with smoke and
starve the motor of air.
The barb has a hose fitted which leads the fumes out the transom via
another ( plastic) barb.
There are no corrosion problems after about 6 years use, mainly because
the barb gets well oiled from the two stroke exhaust.
Klaus

I once drilled a hole in the center of the upper drain/fill plug and fitted
a small hose to it, I then was able to put a sight/fill cup in the boat
above the gearcase height, worked for me this was on a Mercury I/O. The
stainless fill plug has a nylon washer so there is no contact with the AL on
the water side of things, just the oil side.
"mark" wrote in message
...
I would like to tap a barbed fitting into the aluminum gearcase of my
outboard motor. I cannot find stainless barbed fittings and I assume brass
and aluminum touching under salt water is a no- no. If I tap the aluminum
to take a stainless 1/4" bushing and then thread in a 1/8" barbed brass
fitting will there still be corrosion problems. There are several zinc
anodes on the motor and aluminum hull.