Forum: WHALER
  ContinuousWave
  Whaler
  Moderated Discussion Areas
  ContinuousWave: Whaler Performance
  13' Whaler speed w/15-25hp... ?

Post New Topic  Post Reply
search | FAQ | profile | register | author help

Author Topic:   13' Whaler speed w/15-25hp... ?
CC25 posted 09-18-2005 05:51 PM ET (US)   Profile for CC25   Send Email to CC25  
Hi all, looking to downsize my outboard. Currently running a 40 hp 3cylinder 2 stroke merc on my 13. Its way too much motor for how we boat. Lookin for performance with a smaller motor, 15-25hp 4 stroke or 2 stroke, with 2 adults on board.

Any info very much appreciated.

BOB KEMMLER JR posted 09-18-2005 05:54 PM ET (US)     Profile for BOB KEMMLER JR    
what year 13 do you have?
jimh posted 09-18-2005 06:00 PM ET (US)     Profile for jimh  Send Email to jimh     
If you hold everything else constant and decrease the horsepower, the speed will decrease in proportion at an exponential rate of 0.5.
CC25 posted 09-18-2005 06:45 PM ET (US)     Profile for CC25  Send Email to CC25     
Its a 1974. Jim, I'm lucky I can spel.
Binkie posted 09-19-2005 12:01 AM ET (US)     Profile for Binkie  Send Email to Binkie     
jimh. I don`t understand how to work your formula. If my 13 foot whaler goes 38mph with a 40hp, how fast will I go with a 15hp.? How about a 60hp? This could be usefull to me if I knew how it worked. Algebra class was a looong time ago.
Rich
jimh posted 09-19-2005 08:22 AM ET (US)     Profile for jimh  Send Email to jimh     
Q.: If a boat goes 38-MPH with 40-HP, how fast will it go with 60-HP?

A.: Speed is proportional to horsepower raised to the 0.5 power. The increase in horsepower was

60/40 = 1.5

The speed increase will be 1.5^0.5 = 1.22

38 X 1.22 = 46.5 MPH

fast13 posted 09-20-2005 01:22 AM ET (US)     Profile for fast13  Send Email to fast13     
I got my 13 to go 46 mph. 87 40 Johnson mounted 2 inches up,a pair of carbs from a 50,and a 19" Pitch X 12" Ballistic prop. Hooks very hard. Boat leaps out of water from barly on plane, hitting it hard, the stern leaves the water for a few feet before settling down. To duplicate what I have done-you must know how to use trim, and be able to drive through chine walking.

brisboats posted 09-20-2005 03:11 PM ET (US)     Profile for brisboats  Send Email to brisboats     
CC25, Last year I ran my 1966 13 with an 18hp 2 stroke 2002 tohatsu tiller with just me it would hit 20mph with just myself(250#'s) add a large friend boat would still plane off but speed dropped into the 15mph range, add one more person and the boat would not plane at all. I have also gotten the same boat to plane with my evinrude 9.9 2 stroke not sure of the top speed with that motor but seat of pants says low to maybe mid teens. My 1983 25hp 2 stroke mercury tiller pushed the same boat in the low 20's. I hope this info helps.

Brian

JL8Jeff posted 09-23-2005 09:51 AM ET (US)     Profile for JL8Jeff  Send Email to JL8Jeff     
One of my old 13' Whalers had a 1986 Suzuki 25hp on it and that boat moved pretty good. I had no way of measuring speed but it was faster than my cousin's 14' aluminum Starcraft with a 30hp Johnson on it. I have a Johnson 40hp on my 15' Hobie Powerskiff and it moves the boat perfectly fine. The only downside to going with a smaller engine is that you might end up running it at higher rpm's more often to keep the speed up where your 40 will cruise along nicely at a lower rpm. If I had kids that were going to be using the boat, I would max it out with a 25hp motor.
c_mccann posted 09-26-2005 06:19 PM ET (US)     Profile for c_mccann  Send Email to c_mccann     
If speed is a concern and the motor is in good condition, why not just prop down? You would also get better fuel economy, not that it is a problem now.
boatboy posted 10-05-2005 10:14 AM ET (US)     Profile for boatboy  Send Email to boatboy     
I have a 1969 13' with a 25 2 stroke and it runs about 22 or 23 with two 190 lbs guys but I am looking for a larger engine like a 40 or so.

Post New Topic  Post Reply
Hop to:


Contact Us | RETURN to ContinuousWave Top Page

Powered by: Ultimate Bulletin Board, Freeware Version 2000
Purchase our Licensed Version- which adds many more features!
© Infopop Corporation (formerly Madrona Park, Inc.), 1998 - 2000.