Another Stainless vs. Aluminium question

[scottlb]

I couldn't find anything here by searching, so forgive me if this has been covered before ...
I have a 1995 Sea Ray Sundancer 250, with the 5.7L carbed Mercruiser, 250 HP, Bravo 2 drive. I currently have the stock 17.5x23 Aluminium prop on, and also have (came with the boat) a Power Tech 18.5x23 SS prop in very good condition.
I was told when I bought the boat to put the alum. prop on, as the boat is in the water most of the time (take it out in winter for a couple of months) and the alum. prop would cause less corrosion. The water is brackish (Everett, WA), and the boat is run in both salt and fresh water. Does anyone have any experience with this ... or would running the SS prop not make much difference here? Also, any other ideas concerning props on this boat would be appreciated.

 

[tommays]

Re: Another Stainless vs. Aluminium question

If you use the SS porp your merc cathiod system needs to be in perfect condition

It should really be tested with the probe they stick in the water as even in fresh water bad things can happen

 

[TilliamWe]

Re: Another Stainless vs. Aluminium question

Scott, there is definately the risk of more corrosion to your aluminum outdrive if you have a huge chunk of STainless Steel hanging off the back of it.
Have you had any corrosion issues? What condition are your anodes in?
What are your current WOT rpms? If you are not at or near the top of the range under a typical load your 23 pitch SS may lower your rpms down out of the range. Typically, you would want to drop an inch of pitch when going from AL to SS. Yours are the same. But I also notice that the SS has 1 more inch of diameter. What about total blade area? If it's got more blade surface with the increased diameter, it will almost certainly lower you WPT RPMs.
Just be aware that Bravo 2 props are all pretty expensive. Even the Aluminum ones.

 

[scottlb]

Re: Another Stainless vs. Aluminium question

Thanks for the replies, generally confirms what I was told. The boat is home getting prepped for this summer ... unfortunately, I didn't get a chance to do much testing as right after I bought the boat last year we had personal issues come up that pretty much ended our summer fun. Hopefully this year we will get out on the water, and I can do some checking. As the boat spens a lot of time in the water, I may just sell off the SS prop I have and get a spare AL. one, once I see what the current one does in terms of speed/RPM at WOT.
Anodes were in normal shape for 8 months in the water (corroded about 1/2), so changed out all. The two on the trim cylinders were the most corroded, the large on on the front of the drive next, and the round one on the back the least corroded. The prop should be refurbished, I think ... most of the paint is worn off, with some minor pitting on the blades.