4-Blade to 3-Blade Prop

[GuinnessGuy74]

I had a 4 Blade 15x16 prop on my 25' Sundancer w/ Mercruiser 260. I ruined the prop when the hydraulic tilt line ruptured while in reverse and the drive swung up and hit a pole. I replaced it with a spare prop that was onboard when I bought it ( 14.5 x 17 -3 Bladed). Even at 3000 RPM I am going nowhere. Is there that big of a difference between 4 and 3 blades even with more pitch on the 3 bladed one (albiet smaller diameter)? I am not sure what size to get in a 3 blade now.....any help would be appreciated! Thanks<br /><br />Jim

 

[Masher44]

Re: 4-Blade to 3-Blade Prop

Sea Ray would be a good place to start for the recommended prop. On a boat of mine I went from 3 to 4 blade and never went back to 3. When you say you are going nowhere, are you planing? or is it just plowing thru the water?

 

[jimi]

Re: 4-Blade to 3-Blade Prop

Wakeboarders like the four blade to get steady speed when ballasted down

 

[GuinnessGuy74]

Re: 4-Blade to 3-Blade Prop

I am definitely NOT planing......I am doing well less than 10 Kts(almost like a good trolling speed). With the 4 Bladed I was doing 25kts at 3500. Now Past 3000 the RPMs increase too fast with no subsequent increase in speed. Seems like the prop is just spinning. I checked on Mercruiser's Prop selector applet and it recomended an Alpha4 18 pitch. Just not sure why performance would decrease so darn much. Is it possible thatthe drive is messed up? I guess I would know for sure after replacing the prop........<br /><br />Jim

 

[liner85]

Re: 4-Blade to 3-Blade Prop

sounds like your spare prop may have a spun hub?