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West Wight Potter Mailing List maintainer
dfarrell@ridgecrest.ca.us
List hosted by www.tscnet.com
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Eric Henry wrote:
>
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> West Wight Potter Mailing List maintainer
> dfarrell@ridgecrest.ca.us
> List hosted by www.tscnet.com
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> How would one determine the right prop required? I have a 99 merc 2.5 w/ factory plastic prop. Should I change it?
>
> Eric Henry
> P-15
> Trevorton, PA
>
The standard prop on the 2.5 hp Mercury, Mariner, Nissan, Tohatsu (all
made by Marubeni in Japan) has a pitch of 144 millimeters which is 5.7
inches. The optional propeller listed on the Nissan site has a pitch of
7 inches which would make matters worse. The Tohatsu owners manual
mentions an optional propeller with a pitch of 110 mm (4.5 inches).
I think this pitch issue is less of a problem with the small motors. The
2.5 actually operates at a LOWER w.o.t. rpm (Tohatsu says 3800-5200,
Merc says 4000-5000 for the 2.5) than the 5 hp motors, has similar gear
reduction, and a lower pitch propeller.
More subjectivly, I have an '87 Mercury 2.2 which is the older version
of what you have. With the standard prop, the P-15 reaches hull speed at
about 3/4 throttle and "sounds" very happy there, neither lugging or
over-revving. I've towed another P-15 and felt there was still adequate
"pulling" power. We were a little slower getting up to speed but both
boats reached hull speed without using full throttle. Finding the
elusive Tohatsu optional 4.5" prop might give the boat more acceleration
and pulling power but would also increase rpm and noise at cruising
speed and may also increase fuel consumption.
I think that if someone wanted to use the small Marubeni motor in either
it's 2.5 or 3.5 hp configurations to drive the heavier P-19, the 4.5"
prop might be a better choice. There's a fellow who has an Ensenada 20
at the Marina where I often sail. He uses a 2 hp Johnson with a low
pitch prop to drive that boat. You can always tell it's him. He moves at
3-4 kts. and the engine is screaming - It sounds like one of those model
aircraft!
Dave Kautz
P-15 #1632, Tilly Lucy
Palo Alto, CA
This archive was generated by hypermail 2b29 : Fri Mar 31 2000 - 03:27:09 PST