spongy

Propeller - 3 blade or 4 blade ?

Recommended Posts

Hi,

Im just after some advice on propeller choice.

I need to replace my current prop. Set up as follows;

- 4.8m glass cuddy boat

- Yamaha 70hp 2 stroke (about 13 years old).

- WOT runs at about 5000rpm

- Current propeller: TurningPoint Alloy 13.5" x 15Pitch 3 blade

Im after excellent fuel economy and good hole shot and acceleration.

Don't care too much about top end speed, as I spend most of the time cruising at low to medium speeds up to around 25knots.

Im guessing a new stainless steel 3 blade 15" pitch prop, will provide slightly better performance.

Will going to a 4 blade with the same 15" pitch give me any additional benefits? Or will it just drop my WOT rpm too low?

Cheers,

Share this post


Link to post
Share on other sites

Hi there

I'm not the right person to answer your question but I wanted to know an answer.

I did a search on the WWW and found this tec page that may interest you.

Boat Propeller Advice and Tips

Follow This Link

I think it answers your Q well

Hope this helps you make a good choice.

JD

Share this post


Link to post
Share on other sites

Hi there

I'm not the right person to answer your question but I wanted to know an answer.

I did a search on the WWW and found this tec page that may interest you.

Boat Propeller Advice and Tips

Follow This Link

I think it answers your Q well

Hope this helps you make a good choice.

JD

Thanks for the reply.

Yes I kind of knew the benefits of the 4 blade.

Would I see those benefits in the real world, and would the 4 blade put too much extra load on the 70hp 2stroke, which already has its work cut out for it? I would imagine it would knock off a few more RPMs at WOT. The 70hp is probably a touch too small as it is. I don't want to unnecessarily sap more power by using a 4 blade, if it doesn't return any real benefits.

Share this post


Link to post
Share on other sites

I recently switched my props for 4 blade and the improvement was sensational. Boat is over 3 ton with twin 150 verados so obviously a different situation but if you want to send me a PM I'll give you details of who I dealt with. There service was great and they offered to switch them again if they didn't improve performance.

Share this post


Link to post
Share on other sites

Mate I think I have the same motor as you but my boat is lighter. I was having cavitation problems with the stock prop so was looking for a solution. I went with a 3 blade stainless as someone in the know told me the 4 blade was bs. I guess you'll get different opinions where ever you ask.

I don't think I lost any rpm, I may have gained a few knots but the improvements have been great. Cavitation is almost 100% gone and the boat is quicker out of the hole. Cpany I dealt with also offer free exchange if your not happy, or trade in if you chance your donk.

Edited by Alfa-Rosa

Share this post


Link to post
Share on other sites

Spongy I have a 70 Yammie , similar age to yours. The motor came with a 13" prop.

During the test run at hand over there was noticable slippage ( cavitation) with the 13" regardless of the trim setting.

The dealer fitted a standard 15" Yammie prop & problem solved.

Like you , was not all that interested in WOT rev's as I rarely go over 4300 but if pushed the motor will spin to 5300/5400rpm.

Geoff

Share this post


Link to post
Share on other sites

For those who are interested, I got the Solas New Saturn 15 pitch SS 3 blade prop.

Definite improvement from the old prop. Pretty much better everything.

- Smoother

- Better hole shot

- Better fuel economy

- Slightly higher top end speed

- WOT RPM is now 5550rpm

Im thinking I could have gone the 4 blade, as my concern was that my WOT RPM would drop to low with the 4 blade, but I reckon it would drop by a couple of hundred RPM only, which is still ok.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Forum Statistics

    • Total Topics
      63,171
    • Total Posts
      502,849