Re: Nissan 5hp Props

From: Eric Johnson (etj@nwlink.com)
Date: Mon Mar 06 2000 - 00:37:55 PST


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        West Wight Potter Mailing List maintainer
                dfarrell@ridgecrest.ca.us
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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.

Can you tell us more about this device? is it specifically designed for use
with small motors? I've wanted to do the same type of tests on mine using a
little portable tach designed for car engines I had but never got working to
my satisfaction on the small engine.

<snip>
>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

Thanks for the data! I've had the same gut feeling that the stock props on nissan
and tohatsu outboards had too high a pitch for our heavy (relatively) potters.
I think Bill Combes had some experience with this too, and was using a smaller
pitch. I suspect where the smaller pitch will really shine is motoring into
waves and wind.

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