Which impeller is speed and power?

[Gollane224]

I have two propeller, one is 21-m and the other is 23-m marked...
Which one is the speed impeller and which is the power impeller?
Or should i buy 27-m propeller for my 225hp yamaha outboard?

[almetelo]

I guess you mean propeller (not impeller)

Is not that simple (one for power other for speed) but very easy to understand if you google it and read about select a propeller...
Also may search previous posts here on forum.

[throrope]

Props are selected by diameter, pitch, number of blades and shape of blade. Yamaha has developed specific blade shapes for their outboards.

Generally the higher the pitch, the more pulling power you have and less top end speed. Kind of like rear axle ratio's for trucks (the higher the ratio, the more towing capacity, the less top speed, the less mileage).

Lately 4 blade props are very popular and becoming preferred for 4-strokes which have very different power curves from 2-strokes.

A better way is matching your boat and use to your prop. I suggest starting with Yamaha's great performance bulletins. Performance Bulletins | Yamaha Outboards

PowerTech props, a USA manufacturer, works closely with manufacturers and make well respected wheels. They have proprietary software and with a phone call or email will provide you with a selection that you can use to confirm yours or get something more appropriate. PowerTech! Propellers - Official Website - HOME

[rodbolt17]

but at the end of the day the selected propeller should allow the engine to turn at or within 200 RPM of the engines rated max RPM with THAT DAYS load and hull condition.
what it turned with 1 person,1/2 tank of fuel and no gear is IRRELAVENT.

when fully loaded with persons and gear it MUST be able to turn at or near its max RPM.

[Gollane224]

I'll ask another way... Has anybody have a 225hp engine behind 6.5m offshore boat and wich size propeller do you use? What is the top speed and max rpms?

[Gollane224]

Understanding Propeller Pitch | Boating Magazine

If you need more speed, a higher pitch is the way to go.

[TownsendsFJR1300]

I'll ask another way... Has anybody have a 225hp engine behind 6.5m offshore boat and wich size propeller do you use? What is the top speed and max rpms?

Click on the link in post #3 and enter your information. It'll give you a ballpark of what you need, the performance, speed, MPG, etc.

It won't take you 45 seconds...

http://www.yamahaoutboards.com/owner...ance-bulletins

[Bilge Rat]

Select a prop that lets your engine on your boat turn close to the motors max RPM.
If you lug or over rev the motor it is very bad for the motor.

Your speed comes from your motor and prop matched to the load/boat.
To get more speed get a bigger motor.
Slapping a higher pitched prop on just lugs/ reduces max RPM straining the motor with very little if any increase in speed.

Get a prop that gives you near max RPM on your boat/load with the least prop slip. That will give you the best performance.

[Gollane224]

The boat has allready bigger engine that is allowed... I need to play with the propeller do get more speed... The yamaha performance page show's me that it's reccomended pitch 17 and the top speed is 42,3 mph... I had 21 pitch propeller and got 47.3 ph, tomorrow I hope do get more speed with 23 pitch propeller... I'll let you know...

[TownsendsFJR1300]

The boat has allready bigger engine that is allowed... I need to play with the propeller do get more speed... The yamaha performance page show's me that it's reccomended pitch 17 and the top speed is 42,3 mph... I had 21 pitch propeller and got 47.3 ph, tomorrow I hope do get more speed with 23 pitch propeller... I'll let you know...

Question, curiosity,

What maximum, trimmed out, normal operation, RPM's are you getting now?