Go stainless prop or stay aluminum

[specialk]

I have a couple of questions for the good people here. First the background.

- 2008 Glastron GT 185. 18.5 feet approximately 2500 pounds.
- Volvo 4.3 GL 190 HP
- Volvo drive 1.79 : 1
- OEM Volvo prop 14.25 X 23 pitch aluminum.
- total weight of people and gear about 500 pounds.
- all testing @ about 800 feet elevation above sea level and between 70 - 80 F.
- will make multiple runs and find the average speed. All speeds GPS verified.

Results in past years:
- plane in approximately 3 seconds.
- MPH matches RPM from 3000 - 4000 RPM. Meaning 3600 RPM = 36 MPH.
- Top speed 51 MPH @ 4600 RPM.
- Top speed if wife sits on back bench seat instead of front seat 52 MPH @ 4700 RPM. Can trim just a hair more to get more hull out of water.

Aluminum prop appears rough on the ends of the blades like the prop was somewhat sandblasted and pitted. So I tested recently.

Recent results:
- plane in approximately 3 seconds.
- MPH 1 less between 3000 - 4000 RPM. 3600 RPM = about 35MPH.
- Top speed 50 MPH @ 4800 RPM. No matter where the wife sits or how many runs.

Questions:

- is it possible the prop being aluminum can wear enough to show a minor drop in performance?

As we only wakeboard and tube the boat does well for that. If there is a performance gain I would look for it would be for more top end speed.

- as the OEM Volvo aluminum prop appears well balanced for planing and speed reaching 50 MPH, is it worth trying a stainless prop or would the gains be minor? I am not sure a 1-2 MPH gain on the top would be worth more risk of outdrive damage if the prop hit something.

 

[steelespike]

Re: Go stainless prop or stay aluminum

Is the speed by gps?
Calculator indicates a very good 10% slip at 52 mph.The slight change in performance is more likely changes in the motor or hull
or perhaps current,wind, windage ,instruments. The hub in any prop should save the drive i think the key is if the hub doesn't act as it should with ss something else may fail ,hub failure a slim possibility but possible.
Then there is the cost 2 to 3 times as much and the ss costs more to repair.
No doubt the ss will improve performance but based on your performance I wonder how much the improvement will be.

 

[specialk]

Re: Go stainless prop or stay aluminum

Yes it is by GPS. Based on performance with the Volvo aluminum prop, that is why I'm wondering if I would really see much gain from a stainless prop. The performance has dropped a little but you could be right, any small change could be due to any number of things. I was just curious if wear on an aluminum prop could show a slight drop in performance like this.

 

[steelespike]

Re: Go stainless prop or stay aluminum

Aluminum props do wear but we,re talking 10-20 years of operation especially in "dirty" water.