The Evolution Company Inc. - Product Specification

The Evolution Marine Shaft System


Quantitative Data on the Evolution Marine Shaft System
Based on a study by the University of Maine Department
of Engineering and Ultra-Sonic Acoustics Inc., of the
EMSS installed on a 42-foot Grand Banks powered by a
3116 Caterpillar:
83% decrease in hull vibration
40% decrease in horizontal vibration
16% reduction in engine vibration
17 dBA noise reduction at the helm and in aft cabin
Based on a study by Gibbon Associates Consulting
Services of the EMSS installed in a 30-foot Black Watch
powered by twin 350 Crusaders:
"[At] 3200 engine rpm: Measurements indicate
approximately 3 to 16 dB lower vibratory acceleration
levels for the 'after' series, depending on specific
octave band; which would then represent approximately
30% to 60% lower vibratory acceleration..."

The Evolution Marine Shaft System (EMSS) is a complete shaft
system from engine to propeller. It's comprised of two major
components: 1) the "oil-lubricated section" containing a '22'
allow stainless steel shaft enclosed in a 316L stainless steel
shaft log tube with aft bearing housing and forward thrust
bearing housing, and 2) the internal connecting shaft with a
splined slip joint and flexible joints at each end.
Other system components include the engine adapter, mounting
flanges, and monitor tank with its fittings and hoses.
The oil-lubricated section penetrates the hull. Essentially,
it's the shaft enclosed in a non-turning shaft log tube.
Generally, this tube is 316L stainless steel with an
approximate wall thickness of 3/8 inch. It is extremely strong
approaching the tensile and yield strengths of the shaft
At the aft end, near the propeller, this shaft log tube
mechanically mates with an aft bronze bearing housing
consisting of a bearing cap that bolts directly to a mating
bronze flange. This mating flange can be of various designs
depending on whether the installation involves a
sternpost/keel or strut configuration. For sternpost/keel
configurations, the flange can have two or four bolts or
merely be a three-piece locking collar with tabs for bolts.
This flange might only be a three-piece collar machined to
accept the bearing cap and machined to bolt directly to
fiberglass stern tubes or the aft face of the strut barrels.
Within the aft bearing cap are two double lip seals plus a
needle bearing. These operate on their own hardened races. At
the aft end of the shaft log tube, there is a plain bearing.
Additional needle and plain bearings are utilized based on the
application and length of the shaft log tube.
As the shaft and shaft log tube enter the hull, they mate
mechanically with a larger diameter steel thrust bearing
assembly. This thrust bearing assembly consists of a
three-piece housing covering two tapered bearings mechanically
affixed to the shaft and operating within their own hardened
race cones, a front double-lip seal with its own hardened
race, and two double-lip seals -- one in front of the shaft
log tube and an abutting seal in the aft cover of the thrust
bearing housing. The shaft protrudes through the front of this
thrust bearing housing and is keyed to accept a split collar
shaft flange. The forward face of this split collar flange is
machined to accept the bolt pattern of the internal connecting
The internal shaft connecting the oil-lubricated section to
the transmission of the engine can be made from a selection of
solid or hollow metals for weight and operational
considerations.l On each end of this drive shaft,
universal/constant-velocity joints/rubber flex joints by
themselves or combined may accommodate various angles between
the engine and the shaft. Whenever space allows a splined slip
hoke is utilized to facilitate installation and to further
accommodate the "free-floating motion" of a soft-mounted

The Evolution Marine Shaft System is engineered to be as
fail-safe as possible, with an extremely strong, non-turning
shaft log tube containing the shaft, two oil chambers, various
bearings and five double-lip seals.
Once the oil-lubricated section is attached to the hull with
water-tight integrity, either at the sternpost/keel or the
internal bulkhead for a strut configuration, the propeller
thrust is transferred from the engine/reduction gear to the
hull. Because there is no propeller thrust on the
engine/reduction gear, the engine may be isolated from the
hull with truly soft motor mounts. This alone will
significantly reduce engine vibration to the hull and sound
levels throughout the vessel. As much as 83 percent less hull
vibration with a resulting reduction in sound of 17 decibels
has been recorded.
Without propeller thrust on the internal connecting shaft,
this shaft with its flexible joints and splined slip joint may
accommodate various engine shaft angles based on torque and
revolutions of the shaft.
The shaft being held with half-thousandths clearance at each
end, with mechanical bearings in an oil bath, typical
propeller slippage is significantly reduced. The EMSS makes
the propeller much more efficient, which fosters increased
speed and fuel economy. With the shaft and mechanical bearings
turning in an oil bath, shaft drag is at a minimum.
Additionally, the EMSS with its non-turning shaft log tubes in
a strut configuration, eliminates the detrimental turbulence
of water in front of a propeller caused by a turning shaft.
This, too, increases the propeller efficiency.
While greatly improving the environment aboard a vessel, the
EMSS significantly improves propulsion. The Evolution Marine
Shaft System is a long-running, low-maintenance,
oil-lubricated shaft system that truly complements the entire