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With correctly running under water machinery your (boat) vessel will
last longer and run better. Their are no gas stations
on the water, many breakdowns result from problems with these parts!
What is Underwater Machinery?
Underwater Machinery consists of propeller, struts, stern drive units,
bushings, rudders and various other items necessary for the operation
of a boat.
These always consist of metals that have corrosion resistance. Aluminum,
stainless steel and bronze are extensively used.
Noble metals on the Galvanic Scale resist corrosion better that less
noble metals. As in Stainless steel will resist corrosion better that
aluminum.
Underwater machinery must be inspected for collision damage
and(corrosion) galvanic or stray current corrosion damage and wear.
The type of underwater machinery varies from sail and motor boats
to jet skis as does the method of inspection.
Propellers
Propellers are carefully machined, rotate hundreds of times per minute
(RPM) and must be in good condition to give the best performance. Inboard
boats have propellers attached to propeller shafts that (usually) rotate
in a cutlass bearing set in a strut which consist of a bronze sleeve
and a rubber lining.
Propellers are inspected for size and condition. The incorrect
size propeller will impair the boats operation. An incorrectly
size propeller can result in poor performance, transmission and engine
damage. Propellers must be free of nicks, wear and corrosion. Struts
must be securely fastened to the hull and free of leakage at the point
of fastening.
Underwater machinery must be properly grounded to the vessels grounding
system. Cutlass bearings must hold the propeller shaft snug with out
wear or end play.
Stern Drives
The Aluminum casing of stern drive units must be free of corrosion,
it must be without collision damage and must pressure test to a minimum
of15 psi.
Aluminum casing are most susceptible to corrosion damage and must
be protected by zinc. Stern drive units are essentially boat
transmissions and exhaust systems that are submerged underwater.
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Stern drives, continued
The stern drive is filled with gear lube (oil) and must remain free
of water or damage to the internal gears of this unit will occur.
A stern drive unit replaced new can cost as much a $6000 or more. This
can be an expensive item to replace.
Keel & Rudder
Careful attention must be paid to the keel, rudder & rudder linkage,
in addition to the propeller strut and propeller shaft on sailboats. (The
rudders on sailboats are sometimes delaminated).
Wear in not uncommon at the mechanical steering mechanisms of rudders.
Drop centerboard keels must be inspected for corrosion at their pivot
pins and for lateral damage to the trunk. A sailboats keel is most
exposed to collision damage.
A collision of the forward section of the keel will produce extensive
aft damage to the hull.
Problems associated with each of these units remains the same, collision
damage, corrosion, "note; electrolysis is what happens to the
fluid during corrosion not the metal "corrosion and wear.
Key Benefits of a survey
Since underwater machinery drive a vessel, loss of its use will surely
ruin your day and probably cost much more then if the problem had been
corrected prior to use.
Maritime Vessel Surveying, Inc. can provide a detailed
assessment of all the underwater machinery in your vessel.
This inspection is included in our pre-purchase condition survey. It
may also be carried out as a separate assignment for a vessel
owner who just wants his boat checked out.
The pre-purchase survey includes an underwater inspection of
all machinery, using our industry standard equipment. (See Diagnostic
Tools Used)
Please contact our office if we may be of service to you:
Captain Stanley G. Konz, A.M.S.
Maritime Vessel Surveying,
Inc.
1-800-576-9116
If you require immediate support on your vessel, please
fill out the Auto-Responder located on the Contact
Us page and we will get back to you as soon as possible.
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