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Prop for 1995 Johnson 70 on 1969 16' Custom
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| ChrisMA |
Posted on 08/10/11 - 7:14 PM
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My freshly rebuild boat seems to be way over propped. I am running a dry 16' custom with a fiberglass console and lightly loaded (minimal gear and 300 pounds of people) I can't get to full throttle. I stop advancing the throttle at 6k RPM and ~27 MPH for fear of overspeeding the 1995 2 stroke engine. I currently have a 13 3/4" x 15" prop. I *think* I should drop down to a 17" or even a 19" prop, but would rather give up some top end for better acceleration. What would you suggest to move towards? Is there a database here that shows various members boats and their running gear?
Thanks
Chris
Edited by Tom W Clark on 08/10/11 - 9:33 PM |
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| Joe Kriz |
Posted on 08/10/11 - 7:26 PM
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It sounds like you are under propped if you go over the max RPM rating.
What brand of engine?
What brand of prop do you have?
I had both a 15 pitch prop and a 17 pitch prop for my 1985 Evinrude 70. The 15 pitch gave a better hole shot and the 17 pitch gave me a couple mph faster at top speed.
Both props were OMC.
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| ChrisMA |
Posted on 08/10/11 - 7:32 PM
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Joe Kriz wrote:
It sounds like you are under propped if you go over the max RPM rating.
What brand of engine?
What brand of prop do you have?
I had both a 15 pitch prop and a 17 pitch prop for my 1985 Evinrude 70. The 15 pitch gave a better hole shot and the 17 pitch gave me a couple mph faster at top speed.
Both props were OMC.
Joe, the motor is a freshly rebuilt 1995 Johnson 70 hp. I have no clue, but it looks like the stock aluminum prop on the engine. I think I saw OMC stamped somewhere.
I like the low end grunt, so maybe I step towards a 17" prop before I consider a 19" prop. The 28mph top speed seems a little slow, but I know this boat really should have a 90hp engine on it anyway.
Chris
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| Tom W Clark |
Posted on 08/10/11 - 9:32 PM
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The 1995 Johnson 70 has a 2.42:1 gear ratio and 6000 RPM redline. On a classic 16'-7" Whaler it should be good for 36-38 MPH and to do that you should probably be running a 17"-ish propeller unless you choose a Stiletto Advantage or Turbo 1 in which case you would want the 15" pitch models.
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| ChrisMA |
Posted on 08/11/11 - 7:16 AM
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Tom W Clark wrote:
The 1995 Johnson 70 has a 2.42:1 gear ratio and 6000 RPM redline. On a classic 16'-7" Whaler it should be good for 36-38 MPH and to do that you should probably be running a 17"-ish propeller unless you choose a Stiletto Advantage or Turbo 1 in which case you would want the 15" pitch models.
How much benefit an I going to realize with a stainless prop versus a aluminum one in this configuration? Is it just top end speed or more responsive at all throttle settings?
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| Tom W Clark |
Posted on 08/11/11 - 7:29 AM
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A stainless steel propeller may be a little faster at the top end but most of the benefit will be better grip, acceleration, handling and fuel economy.
It will also last much longer.
Just be sure your motor is mounted at least two holes (1-1/2") up on the transom.
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| ChrisMA |
Posted on 08/11/11 - 7:37 AM
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Tom W Clark wrote:
A stainless steel propeller may be a little faster at the top end but most of the benefit will be better grip, acceleration, handling and fuel economy.
It will also last much longer.
Just be sure your motor is mounted at least two holes (1-1/2"  up on the transom.
I tried to do that, but my lower holes would not align. I know I have to fill and redrill, but that is a winter project. If I am going to run all the way down, should I stick with aluminum?
chris
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