We just completed replacing the Mercruiser 260 RH with an Indmar 310
hp 350 LH in our Concorde 27'. At the same time we had the Velvet
Drive 71C 1.53:1 rebuilt and the pump reversed. The rebuilder said
there was nothing wrong and just replace the relevant clutches, etc.,
reversed the pump (for $800). During the sea trials, we noticed that
the transmission now makes a wining noise in reverse that wasn't there
before. The enginge / tranny / packing box / strut appear to be in
alignment. In addition, we noticed a vibration at 4000 rpm although
that could be the result of a gross mismatch in prop by one of the
local "experts" that allow the engine to get to more than 4800 rpm in
less than a second. (Only once by mistake -- we're still breaking in
the engine.)

Both the mechanic who did the final electrical connection and the
transmission rebuild house said that was normal. Of late however, my
faith in the veracity and knowledge of marine mechanics / supply
houses has been shaken to the point that I think if my boat was under
20 feet of water they would tell me "that's normal".

Is the reverse whine normal? Should I be worried that the vibration
will make a big hole in the bottom of the boat?