Right Prop

[JeremyNeale]

Hi,<br />I am trying to determine the prop that will work best for my boat.<br />It's an 18ft GlassPar with a 4 cylinder classic 50. I am currently getting 6100 rpm, 24 Mph from a 10 pitch aluminium.<br />It seems I need more pitch but how much? <br />Any thoughts much appreciated.<br /><br />Jeremy

 

[rickdb1boat]

Re: Right Prop

Jeremy<br /><br />Since your RPM's should really be around 5500-5700, I would go up to a 13" pitch to get you right where you need to be. Every 1" you go up in pitch = 200 RPM's less. You may see a small increase in speed if the motor is up to it and the boat is not too heavy. Those Mercs were not meant to turn that high of RPM. I'm sure you know this, from the way it sounds.

 

[fishinhole]

Re: Right Prop

For every 2in. of pitch you can figure apprx. 200-300rpm change. Also if your prop is not cupped, that can change rpms about the same

 

[rickdb1boat]

Re: Right Prop

As fishinghole said, 1" =200 RPM change, as well as the amount of cup on the prop. Also, in addition to that, it depends on the brand of prop as to how your boat will react to the change. What brand are you running now? It's possible that if you go to a prop shop, they may have one they will let you try out for free or possibly a small deposit, if they are pretty sure you are going to buy from them. Couldn't hurt to give it a try.. And ask for their advice. They are the ones that know the most...