Welcome, Guest
Username: Password: Remember me

TOPIC: Prop questions...again.

Prop questions...again. 04 Aug 2018 22:26 #87303

  • VinTin
  • VinTin's Avatar
  • Away
  • Quartermaster
  • Quartermaster
  • Posts: 4493
  • Karma: 36
  • Thank you received: 1157

chriscraft wrote: So I went ahead and purchased a 10 3/8 x 13 pitch and it raised the RPM's to 4300 max (from around 3900) and increased the speed to 26.5 mph max (according to GPS). Manufacturer max RPM is 4500 so I guess 4300 is probably the best it can do. Overall satisfied with it.


You still need to aim for 5000 RPM with you in the boat alone. I would look for a 12 or maybe a 12 and a half and give it a try. At the RPM you're turning, if you have four people in the boat you will be seriously lugging your engine. This is the same advice you would have been given 60 years ago when these motors were made.
The following user(s) said Thank You: chriscraft, jabe

Please Log in or Create an account to join the conversation.

Just beyond the breakers.

Other 1/2-195something Flash - KG7
Last edit: by VinTin.

Prop questions...again. 04 Aug 2018 14:50 #87299

  • jabe
  • jabe's Avatar
  • Offline
  • First Mate
  • First Mate
  • Posts: 4703
  • Karma: 36
  • Thank you received: 1339
i have heard for every inch decrease in pitch, rpm's increase around 3-4 hundred...........i assume based on a standerd factory prop
since getting my tiny tach, i was able too record the change in rpm from pitch too pitch, i am now running an 11.5 and getting 4400-4500 rpm..........
The following user(s) said Thank You: chriscraft

Please Log in or Create an account to join the conversation.

57' Fleet Ranger111-
57' Fleet Cartopper-
53' Deluxe Runabout-
56' Johnson's...Javelin, 2 x 30,15, and 7 1/2 hp
we have not inherited the earth from our fathers, we are borrowing it from our children

uppercanadachapteroftheaomci.yolasite.com/
Last edit: by jabe.

Prop questions...again. 04 Aug 2018 11:43 #87292

So I went ahead and purchased a 10 3/8 x 13 pitch and it raised the RPM's to 4300 max (from around 3900) and increased the speed to 26.5 mph max (according to GPS). Manufacturer max RPM is 4500 so I guess 4300 is probably the best it can do. Overall satisfied with it.
The following user(s) said Thank You: HawkEyes

Please Log in or Create an account to join the conversation.

Prop questions...again. 18 Jun 2018 15:14 #85885

Service manual states WOT is 4500 rpm. Would the 13.25 get it close to that?
Again, tough question.

Please Log in or Create an account to join the conversation.

Last edit: by chriscraft.

Prop questions...again. 18 Jun 2018 12:25 #85884

chriscraft wrote: Very minimal load and just myself at 220 lbs. Would it be possible for the 13.25 to increase the rpms upwards of 1000?


Going from a 14 pitch to a 13.25 pitch I don't think will increase it 1,000 RPM, more likely 400-500 RPM. The other variable is, will the speed increase? That will add RPM's as well.

I'm not sure of the gear ratio of the older lower unit, if someone can provide that this calculator will give a very close estimate of the change.

www.rbbi.com/folders/prop/propcalc.htm

Please Log in or Create an account to join the conversation.

Ray

"Every man takes the limits of his own field of vision for the limits of the world."
Arthur Schopenhauer

1956 Vagabond I - 50 HP Johnson
1950 Flyer - 50 HP Evinrude
1/2-195something Flash - KG7
1956 Golden Rocket, Sawzall Special
Last edit: by Locomotion.

Prop questions...again. 18 Jun 2018 11:04 #85883

Propeller options for that motor (in regards to pitch) are 14,13.25, 12.5 or 11.5.
I know where I can find a new OEM 13.25.

Thanks
Mark

Please Log in or Create an account to join the conversation.

Prop questions...again. 18 Jun 2018 10:58 #85882

Very minimal load and just myself at 220 lbs. Would it be possible for the 13.25 to increase the rpms upwards of 1000?

Please Log in or Create an account to join the conversation.

Prop questions...again. 18 Jun 2018 00:27 #85879

  • VinTin
  • VinTin's Avatar
  • Away
  • Quartermaster
  • Quartermaster
  • Posts: 4493
  • Karma: 36
  • Thank you received: 1157
I'd try a 13.25" pitch.

Maybe even a 12"

Aim for a wide open rpm to be almost right at 5k with a lightly loaded boat and just you in it.

That way when you have passengers and more of a loat the motor will still be in it's safe operating range. 3,900 rpm is too low and is not good for the motor.

How was you boat loaded?
Just you and gear?

Please Log in or Create an account to join the conversation.

Just beyond the breakers.

Other 1/2-195something Flash - KG7
Last edit: by VinTin.

Prop questions...again. 18 Jun 2018 00:04 #85878

So I put another couple wraps (total of 4) around the plug wire. That seemed to settle it down. Here is the skinny on the my prop situation with the new information.
WOT rpms in the 3900 range.
Top speed just under 25 mph with the 14 pitch prop.
Plugs are a perfect brown indicating I have the carb dialed in.
So do I go to the suggested 13.25 pitch is my question.
Thanks to all for your input.
Mark

Please Log in or Create an account to join the conversation.

Prop questions...again. 17 Jun 2018 20:58 #85873

jabe wrote: mine wasn't bad, i was comfortable if it altered a couple hundred rpm, least i know what ball park i am in, it did do a couple 1000 rpm jumps that had me concerned.........i will look into sheilding the wraps on the wire and see what happens


You can wrap a wire around the other plug wire and ground ONE end and cut way down on the RFI it is putting out.
The following user(s) said Thank You: jabe

Please Log in or Create an account to join the conversation.

Ray

"Every man takes the limits of his own field of vision for the limits of the world."
Arthur Schopenhauer

1956 Vagabond I - 50 HP Johnson
1950 Flyer - 50 HP Evinrude
1/2-195something Flash - KG7
1956 Golden Rocket, Sawzall Special
Time to create page: 0.180 seconds

Forum Statistics

  • Total Users:1768
  • Latest Member:BK
  • Total Posts:80.8k
  • Total Topics:6344
  • Total Sections:9
  • Total Categories:22
  • Today Open:1
  • Yesterday Open:0
  • Today Answer:13
  • Yesterday Answer:13

Top Posters

Top Posters Posts
jabe 4703
VinTin 4493
Eagle127 4482
sgower 4441
Boatboy 3404
Locomotion 3269
BigBadJon 3077
Carol 2900
unclbuz 2698
Bikecop1 2454

Contact

How to get ahold of Us

www.featrcraft.net Command Central
52457 Robins Drive
New Baltimore, Michigan 48047

Webmaster

Steve Gower
This email address is being protected from spambots. You need JavaScript enabled to view it.

 810-614-0734

Support

for support
This email address is being protected from spambots. You need JavaScript enabled to view it.

 

Events

Event Coordinator
This email address is being protected from spambots. You need JavaScript enabled to view it.

 

property of:

Feather Craft Technologies - Copyright © 2016 www.feathercraft.net