"Learning" Nissan 5HP & prop pitch

Bill Zeitler (WZeitler@compuserve.com)
Fri, 10 Sep 1999 20:15:52 -0400


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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,

I used to be WWP-15 # 2060 " Just Wight "...Wilmington, Delaware and used
[ of all things ! ] a 62 pound Honda 5 HP/ 4 cycle [ with reinforced
transom ! ].

For more then I want to go into [ and more then you want to hear ] I now
have a 1,000 pound Nimble Bay Hen [ 21 feet LOA ]...and still use the Honda
5.

The standard prop is a 3 bladed 7 7/8 diameter with pitch of 7 1/2.

After some study and discussions with others of more experience I bought
the " workboat prop " of the same diameter but a lower ptitch [ 6 11/16
inches ]. I was told it coupled with the water better for the heavier
boat.

I " think " I can tell the difference [ for the better ] but it might be my
imagination. Less cavitation ?

The origional prop is now an emergency spare...so I'm only out about $
50...and it's nice to have a spare prop on board.

Bill Zeitler [ also an EE....howbeit retired ]
Highly modified Nimble Bay Hen 21 catboat " Amenity "
ECPA

PS: When I go "instantaniously" from slow or idle rpm to high rpm here
is also a " hickup " period...but only of a second or two until it "
catches " and the high rpm takes over. Except for that [ and it is not
really a problem] ..I'm happy with the Honda 5/4 cycle ].