3 blade vs 4 blade props

[captcrunch]

Need to replace the props on my 38c, as it turns out the boy has had the wrong size props since I bought it. Was given options in 3 and 4 blade. Anyone have recommendations one O’Leary or another, the wrong size ones were 4 blade

 

[madhatter1]

3 BLADE- Louder, more vibration, better top speed
4 BLADE- quiet, smooth, slightly better cruise speed, less top speed.

 

[SEVEN]

4 or 5 never a 3

 

[oceanjake]

Seven, what are the advantages of 5 blades?

 

[SEVEN]

No vibration. Smooth. Very very expensive

 

[34Hatt]

No vibration. Smooth. Very very expensive

So Very very Expensive is now a advantage

I went with 4 blade very very Happy

 

[captcrunch]

Tried a set of proper sized zf CBC machined 3 bladders last night and picked up 3.5 knots. Didn’t realize how bad the wrong size prop affects performance. Still running hot on exhaust on starboard , so have to investigate further. Also not pulling wot

 

[Fanfare]

I went from my Hatteras factory original three blade props to four blade when I re-engined about 25 years ago. I was immediately struck by the huge improvement in maneuvering at idle speed. Using the clutches to enter or leave a slip gave an instantaneous result. The old props seemed to spend a second or two just spinning before the boat would react. Four blades were much better. They dig right in and move the boat.

I am discounting both the added horsepower from my new engines (not present at idle) and the slight change in gear ratios from my new Twin Disc transmissions. I believe it all comes from the propellers.

 

[SEVEN]

So Very very Expensive is now a advantage

I went with 4 blade very very Happy

Good catch.

 

[kelpy]

Tried a set of proper sized zf CBC machined 3 bladders last night and picked up 3.5 knots. Didn’t realize how bad the wrong size prop affects performance. Still running hot on exhaust on starboard , so have to investigate further. Also not pulling wot

If you haven't done so recently, you should get your engines tuned prior to final prop testing/ decision.It can make quite a difference at cruise and top end. The engines have to reach full RPM at WOT.