Target RPM?

[2.5-21]

What is optimal RPM to prop a 300X?

Quote from Dave Bush.... (the X rev'd to 7000 with more after peak power (over-rev) )

[moatorbotin]

I recall when I had my 300x a lot of guys were talking about propping them to 6500 or so saying that they were actually faster that way than propping to the limiter. Life circumstances and melted pistons never allowed me to test that theory out myself. This was in say 2008-2009 that I recall this, so my memory could be off.

Non-helpful post that may offer something to chew on.

[Wild Bill]

Long story, I hgave an X on a Obsession Vortex 21. I have tried props from 26-32 on it. Thought i would be smart and put a 26 PP drag 4 for the smaller lakes and wined it up to the govener for high 90,s at 7100, nope only spins it to 66-6700 and hits a wall. Swaped for a 28 drag 4 same rpm more mph 97 plus mph. 32 drag 4 105 mph at around 6300 with a long river to run and i mean long run. Favorite prop a tweaked 15x30 Hoss HPD runs just oner 100 at around 6300 but will haul my self and my wife their.
My exerience shoot for the biggest wheel you can spin to 62-6300 rpm. I thought it would spin that 26 to the govener quick but it just cant move enough air upstairs. It seams like it kas COPD or something. I call it my Cummins it makes the power not the rpms. I wish it ran like my drag.

[Wild Bill]

All mph are right tac readings are close. I don't have a recall tac and don't have a lot of time to watch it when flying down the lake. And the engine is healthy. Hope this helps.

[2.5-21]

Long story, I hgave an X on a Obsession Vortex 21. I have tried props from 26-32 on it. Thought i would be smart and put a 26 PP drag 4 for the smaller lakes and wined it up to the govener for high 90,s at 7100, nope only spins it to 66-6700 and hits a wall. Swaped for a 28 drag 4 same rpm more mph 97 plus mph. 32 drag 4 105 mph at around 6300 with a long river to run and i mean long run. Favorite prop a tweaked 15x30 Hoss HPD runs just oner 100 at around 6300 but will haul my self and my wife their.
My exerience shoot for the biggest wheel you can spin to 62-6300 rpm. I thought it would spin that 26 to the govener quick but it just cant move enough air upstairs. It seams like it kas COPD or something. I call it my Cummins it makes the power not the rpms. I wish it ran like my drag.

26- 32 is a lot of prop pitch difference!

[Wild Bill]

Yes was trying to spin the 26 to the 7100 rpm governor but it just wouldn't do it. In my own uneducated opinion it isn't a good air pump above 6300 rpm. It just hits a wall. So i give it what it wants and try to take advantage of the torque. That 32 is kind of a slug unless i am light and by myself,not a good all around prop for my set up.

[Double Rigged]

My testing with my boat and 300x motors support what Dave Bush has proved on his website using the engine dyno. My current set up and RPM band depending on loads is from 6700-7000.