Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: Need prop pitch advice 15 sport w/ 70 Evinrude
Posted by waterbug on 06/27/11 - 2:57 PM
#1
I have a 1981 15 Sport that I just put a 1997 70 Evinrude. The two props I have are 15 and 17 pitch, not good for my set-up. Was thinking 19 or so. What are you experts thinking? I did just borrow a 20 pitch stainless Raker to try out tonight. I'm just not sure....
Posted by Joe Kriz on 06/27/11 - 3:03 PM
#2
How do you know these props aren't working properly?
What WOT is your tachometer showing?
What kind of setup do you have?
We need a little more info on your RPM's at WOT.
You might also look at this post but still you would need to view your WOT when testing to determine if the RPM's fall within the manufacturers specs which are 4500 to 5000 RPM's....
http://www.whalercentral.com/forum/vi...d_id=12219
Posted by waterbug on 06/27/11 - 3:05 PM
#3
I'm hitting the rev limiter. My tach isn't working. I'm trying to figure out how to hook it up, that would sure help in trying to prop it right...
Posted by Joe Kriz on 06/27/11 - 3:07 PM
#4
Is your charging system working?
Do you have a must have voltmeter to know your charging system is working.
If your charging system isn't working this could be causing your tach to not work correctly either.
Their are 3 wires on the tach.
Black is ground
Purple is 12V key on power
Gray is the pulse from the engine.
Posted by Tom W Clark on 06/27/11 - 3:09 PM
#5
A 1997 Evinrude 70 has a 6000 RPM redline and a 2.42:1 gear ratio.
On a 1981 Sport 15 you will want to have a 13-7/8" x 19" BRP Viper or a 13-1/4" x 17" Stiletto Advantage.
Be sure the motor is mounted two or three holes up leaving about 1-1/2" or 2-1/4" of space between the top of the transom and the motor mounting brackets.
Posted by waterbug on 06/27/11 - 3:19 PM
#6
Charging system works, tach just isnt hooked up. I just went and grabbed an 18 pitch stainless raker from the dealer too. He just happened to have both of these used...
Posted by Joe Kriz on 06/27/11 - 3:22 PM
#7
Good.
Tach is easy to hook up like I showed above.
You should have those 3 wires in the engine harness at the control box.
Yes, I was thinking my 1985 Evinrude 70 was 5500 RPM.
My 1986 Evinrude 70 twins were 6000 RPM
Posted by dgoodhue on 06/28/11 - 3:04 AM
#8
The rev limiter on my 1989 60/70 service manual says its at 6700rpm. The design of the motor did not go through any major changes through 1998, so I would suspect it the same.
Posted by Tom W Clark on 06/28/11 - 11:40 AM
#9
For the record, the Johnson and Evinrude 70 HP two strokes were made in two different versions.
From 1974 through 1985 it was a 49.7 cu. in. block with a 5500 RPM redline.
Starting in 1986 and continuing through 2001, OMC bumped up the displacement to 56.1 cu. in. and raised the redline to 6000 RPM.
The gear ratio on both motors was always 2.42:1.