Re: "Learning" Nissan 5HP & prop pitch

Dan Rickert (drickert@thegrid.net)
Mon, 13 Sep 1999 09:15:25 -0700


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West Wight Potter Website at URL
http://www.lesbois.com/wwpotter/
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>Date: Fri, 10 Sep 1999 16:07:36 -0700
>To: rye gewalt <ryeg@vais.net>
>From: Dan Rickert <drickert@thegrid.net>
>Subject: Re: "Learning" Nissan 5HP & prop pitch
>In-Reply-To: <37D97ACE.CC188EF2@vais.net>
>
>At 05:40 PM 9/10/99 -0400, you wrote:
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>> West Wight Potter Website at URL
>> http://www.lesbois.com/wwpotter/
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>>I have a Nissan 5HP that I bought this season and I am very happy with
>>it. It has one characteristic that I find both interesting and
>>perplexing. When you make a drastic change in the engine speed, the
>>motor runs rough for a few seconds (20 maybe) and then settles down to
>>nice smooth operation. I wonder if any of the other Nissan (Tohatsu,
>>etc) owners experience this?
>>
>>The Carburetor has no adjustments except for one which I assume has to
>>do with initial/starting gas supply -- all the other stuff appears to be
>>sealed. I am used to the old carbs where you had several screws to play
>>with. I wonder if there are some internal "smarts" built into this new
>>fangled carb that I don't understand or if the effect noted above is
>>just the motor clearing itself up internally for the new speed.
>>
>>Nothing is simple anymore.
>>
>>Otherwise I really like my Nissan and am interested in hearing more
>>discussion about going to a lower pitched prop. Does using a lower
>>pitch make the engine more efficient at cruising speed -- i.e. does it
>>run slower because the prop is more effectively coupled to the water?
>>Or what is the advantage of the lower pitch. I'm an electronic type and
>>can't quite get my arms around the concept.... If some of you
>>mechanical types can explain it to me, maybe I can tell you about Ohms
>>law or one of those other theoretical 'lectronic things.
>>
>>Fall is here on the Potomac, the temperature and humidity are down and
>>the wind is up. Yippie!
>>
>>Regards
>>
>>Rye Gewalt
>>1990 HMS 18 Grace II
>>Springfield, VA (WSM on Potomac R.)
>>
>>
>>Rye a lower pitch means the engine revs higher. Like putting a car in a
lower gear. The pitch is the amount of foreward motion theoreticaly that
the prop would move foreward in one revolution. Like the pitch in a screw
or bolt. The advantage with a heavier boat is that it allows the engine to
rev up to its most efficient opperating rpm. Kinda like impedance matching
two circuts. Two stroke engines have a very narrow band of rpm at which
they make max horsepower. If you load the engine below this range it falls
off in power and effeciency. HTH
Dan Rickert
Almanor Import Repair
Clear Creek CA (Northern)
I have no quarrel with those who work cheaper than I do, I figure they know
what they are worth.