(Nice post snipped)

chuckleYou are very right in rather graciously implying with an
admirable level of restraint, that a lifetime of acquired prejudice in
one sector of marine life may or may not be detrimental when applied to
another.

It happens that we lucked out for the time being with this one by
acting like commerical guys, by the grace of God, though we got damned
dirty & tired doing so. ;-) Seems we're not 32 anymore.

By similar Providence the associated hoses, diverter, macerator & etc.
are in good serviceable cond. Sort of "a stopped clock is right twice
a day" evolution. ;-)

A foundational problem is this instance is that of a '70's boat never
envisioned to need MSD, backfitted with a tank that entirely fills the
only reasonably avail space without extensive mod, which is still only
1/2 the capacity of present-day practice, i.e. 45 USG/37' LOA
motorsailer. I'm sure you've seen this movie 1,000 times, perhaps
minus the same humorous cast of characters.

Off-the shelf poly options reduce this to 30 USG on a good day.

Were she mine, I'd consider a more extensive mod to fit more tankage of
less unusual dimensions.

Good news is she has a free berth alongside a commercial cargo terminal
that has great heads inside. :-)

Yes, austenitic SS has pitted in MSD use since we first though it'd
work well in '76. (You should've seen the other & bigger boo-boos we
made with early commerical MSD's.) We can get it fabbed for free,
though, & flush & repassivate it view she will only be afloat 3 mos/yr
for the next decade.

Another issue/question arose during this minor Chinese firedrill:
urethane foam. Tank had been foamed in-place for support. Naturally
this made it a b*tch to break free & remove, given nearly no working
clearance (with an unscheduled main halyard "stress test" in the
bargaing). But I am unclear as to the use of unprotected/un-enclosed
urethane foam aboard a yatch. You can't even do this ashore in a
house, though there is so much other dangerous stuff to burn in a yacht
that maybe it is moot. It there a r/b guideline or other generally
accepted practice relating to its use aboard a yatch, which you may be
aware of? BTW carpenter ants looouuuuvv urethane foam, too, as a
preferred multi-unit condo, and they will find it even if it is under
concrete on all sides or 25' off the ground inside a structure.

BstRgds,
- f.