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West Wight Potter Mailing List maintainer
dfarrell@ridgecrest.ca.us
List hosted by www.tscnet.com
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I found that the new Nissan 5hp 4-stroke motor on my P-19 didn't seem to
sound like it was getting to the proper high-end RPM. Or - I did not yet
know how quiet these 4-stroke motors really were. So -- I decided to get
an RPM reading on the motor under full power with the stock 8" pitch prop.
Gut-feel, knowing this motor needed a lower pitch prop, I purchased the 7"
pitch prop and had it with me prior to starting the stock prop test.
On Sunday morning, after the Saturday 02/26/2000 "canceled" (except for
some die-hards needing, as Jerry B. states it, "a water fix")
Potter-Yachter outing in the Oakland estuary, I was able to determine the
following:
Prop Full Throttle RPM Speed
8" 4400 4.8 kts
7" 4900 5.4 kts
(sorry if my column "tabs" mess up this data)
The RPM was taken with a Sears Engine Analyzer (12V required) using an
inductive pickup. Its accuracy is unknown. The speed calculations were
obtained averaging GPS readings for four quarter mile runs with each prop,
two down-river and two up-river. Accuracy is again questionable, but my
point was to show the needed higher RPM on these 5hp motors.
Nissan recommends 4500-5500 RPM for optimum high-end operation. Our 19'
Potters are heavy enough to warrant the 7" pitch props vs. the standard 8"
that comes with all new motors. By copy of this note to IM, I'd like to
recommend they ask Nissan to supply their new motors with the lower pitch
prop. If buying a spare prop, I would again recommend the part
#36964-5141M (7" pitch).
The Nissan Owner's Manual states their prop sizes as 200x229mm (7.9"
diameter x 9.0" pitch), 200x200mm (7.9"diameter x 7.9" pitch) and 200x178mm
(7.9" diameter x 7.0"pitch). The "Tech_Talk" prop section of their
web-site has a misprint on the 8" pitch prop showing 7.2" vs. 7.9". That
web-site is: http://www.nissanmarine.com/tech_talk/prop_chart2.html
The 5hp prop part numbers are as follows:
7" pitch 36964-5141M
8" pitch 36964-5162M
9" pitch 36964-5181M
Fair Winds and fun Pottering,
Dave Norris, P-19 #1004 "WightCap"
Los Gatos, CA
This archive was generated by hypermail 2b29 : Fri Mar 31 2000 - 03:27:09 PST