Too many rpm's or just right

[rcaudlej]

I have a 2006 Yamaha 175 hpdi 62hl-1000996 and I normally run a 23m yamaha pro series prop about 5500. I recently bought a 22 pitch mercury Tempest turning about 5800 rpms. Full operating range is 45-5500 but the rev limiter goes off at 6200. The engine seems to run better than ever at 5800. Am I hurting anything or should I stay with the 23. Fuel consumption is immensly better with the 22.




Robert

[amahaork]

How big and how heavy your boat? I'd try it myself if fuel consumption is immensly better

[rcaudlej]

RPM's

Ranger 188vs Bassboat 63.1 @ 5800 and 1500lbs

[boscoe99]

Just because the pitch of a propeller will allow a motor to over speed does not mean that the operator should let it. You are in control of the throttle aren't you?

The air is cold and dry now. Come the high temperatures and humidity of summer you might find that the 22" pitch propeller won't allow the motor to reach 5500 RPM.

I doubt that running your model at 5800 will hurt a thing other than the long term life. The VZ250 originally has a redline of 5500 RPM. It was increased to 6000 RPM. No change in engine life.

I suggest that if a motor bounces off the rev limiter the pilot is not doing his job.

[BQUICK]

Surprised that fuel mileage is better with the 22. The 23 should only drop rpms a few hundred and still be close to 5500 at full throttle.

Kinda like saying a car gets better mpg in 3rd gear vs 4th.....but then again a car is running light load.

[boscoe99]

There are so many variables involved when it comes to propellers that it is sometimes difficult to make sense of results seen. Pitch is just one of the variables. Blade geometry, diameter, material, rake, cup, are just a few. These differences can cause the same size diameter propellers to have vastly different slip percentages which can affect economy.

Even within some specific brands and models (Yam Saltwater Series II for instance) the diameter can change as the pitch changes. So, more than just pitch has to be taken into account when testing different propellers of this type.

What one maker will call a 22 pitch propeller another maker might call a 21 or a 23 pitch.

People are always wanting definitive information when it comes to their desire to select and try a different propeller. My experience has been that the only way to know how any given propeller will perform is to test it.

What works great for one guy will be a dog to another guy. Even if the boat and motor combination are precisely the same.