# What prop for my Honda 15hp four-stroke to go faster?



## mkhsurf (Jun 11, 2009)

BF15 honda on my classic. Just want a little more top end speed. wondering what my options are and how much a new prop could help?
Suggestions?
Thanks


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## Brett (Jul 16, 2008)

First the specs

Type  4-Stroke SOHC 2 Cylinder/4 Valves
Displacement 350 cc (21.4 cubic inches)
Bore & Stroke 59 mm x 64 mm (2.3 x 2.5 inches)
Full Throttle RPM Range 4,500-5,500 RPM
Rated Power 15 HP @ 5,000 RPM
Cooling System Water Cooled
Fuel Delivery 1 Carburetor
Ignition System PGM-IG
Starting System Electric/Recoil
Exhaust Through Hub
Lubrication Wet Sump
Trim Range 4 Stage 8°-12°-16°-20°
Tilt Range 72°
Drive
Gear Ratio 2.08:1

Then the process:

1) Install a tachometer
2) Run the boat with a light load and determine the full throttle rpm with the existing prop.
3) A change of 1 inch of pitch will produce a change of about 200 rpm
    more pitch means less rpms, less pitch means more rpms
4) Buy a prop with the pitch that will give you 5200-5400 rpm at full throttle.

Previous post:

http://www.microskiff.com/cgi-bin/yabb2/YaBB.pl?num=1260548288/1#1


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## noeettica (Sep 23, 2007)

For now forget the prop !

The motor is the same displacement as a 20 Hp I bet a carb change will wake it up then follow brett's sugestions ... That motor should be able to Run a 12.5 pitch prop ...

Keep us posted 

Dave


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## mkhsurf (Jun 11, 2009)

Thanks for the info.. I hadnt even thought about carb adjustments. Thanks guys. Is there a carb kit you had in mind? What basic components would I need to wake her up!!?


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## Brett (Jul 16, 2008)

You get to enjoy playing "Whats different in these two pictures?"

http://www.boats.net/parts/search/Honda/Outboard%20Engine/parts.html

Find your year and model
then check the carb, block, head and exhaust part numbers
against the part numbers of the same year 20 hp Honda.
Those parts that have different numbers are the ones to replace.


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