Wich 4 blade propeller to buy..? Please advice.!

[Sandro]

HI

I have 1994 Ski Nautique with PCM Pro Boss engine. I want to change my 3 blade propeller with 4 blade. I need an advice: what should I check and what should be considered when changing the propeller.

Thanks

[Mamigacz]

When you take the old prop off, record the shaft diameter, if its keyed or splined, prop diameter and pitch. Here is an example:

13x12 means 13” prop diameter x 12pitch

Usually the pitch will remain the same. However if you are buying new, call the prop manufacturer and ask for a recommendation. They will probably be interested in your maximum RPM at wide open throttle. My original set up was 13x13. I bought an ACME three blade prop and they recommended going to 13x12.

I hope this helps.

[SoldTheBayliner]

I live at a higher altitude and I know they usually recommend a pitch change for more torque at my altitude for pulling someone out of the water...you take a hit on top speed though.

[jsta281]

to figure it out exactly you need to know what current prop Specs are and manufacturer. You also need to log rpm and speed at wide open throttle.

however having asked these questions several times of the resident prop guru TRBenj I can tell you that if you are RH 1" bore and your boat makes the expected ~285 hp with a 1:1.23 trans you are most likely looking at a ACME 422. (12.5- 15.5- .105). Slightly less pitch would be the ACME 654 (12.5-15-105). If you wanted to stay with a 13 dia prop you would go with the ACME 224 (13-15.5-.09)

[Sandro]

Guys thank you a lot for your replies. Im pretty new in this field. Just bought the boat last summer. Also, in my country , where I live, this type of sport is not so popular. Thats why we have no people who can give me some advices and you know.. Also, we have a lack of technical persons who can really help me with the technical issues. As I mentioned here, I bought Ski Nautique 1994 last year in perfect conditions. Absolutely no technical issues except the problems with high RPM after ignition ( Ive post a topic with this problem here http://www.planetnautique.com/vb3/sh...M-351-Pro-Boss ). BTW, if you have any ideas regarding this problem please advice. I will highly appreciate that.

OK. Back to the propeller. I have a question about transmission type. What does 1:1.23 trans means..? and where can I find out my trans type..?

Thanks

[jsta281]

In my previous post I referred to a 1:1.23 trans when actually I mean a 1.23:1 trans in other words for every rotation of the drive shaft the prop turns 1.23 times. This results in better hole shot. I'm pretty certain your boat has the 1.23 trans.

You really need to do some tests with what ever your current prop is documenting with a GPS your top speed your max RPM at top speed and elevation. That data in com inaction with what motor and trans will confirm or eliminate my previous speculation.

[Lewy2001]

Actually it is the other away. It is a gear reduction box it requires the the engine to spin 1.23 times to get 1.0 rotation of prop shaft and prop. This is why they can run props with a bigger diameter and more pitch.

[Sandro]

Many thanks for helpful advice. I will make a test as soon I get my boat in the lake. I will make some photos of my spare propeller which came with the boat and make measurements as well.

Thanks

[jsta281]

Lol ya I went to bed thinking I said that wrong came on here to correct it this morning, glad someone corrected it.

[jsta281]

Having a reduction box is like being in third gear as apposed to 4th gear in a car.