Stainless = speed?

[crackerjack]

I've got an 18' bowrider with 135 horse mercruiser, alpha drive, turning a 19p aluminum prop tops out about 40 mph at just over 4800 rpm. <br />If I put on a stainless 21p prop what kind of top end could I expect to see? <br />I've plugged it into a prop calculator, but most don't consider the additional efficiency your supposed to get from stainless.<br />Anyone got experience doing this?<br /><br />Thanks for any feedback!

 

[stevens]

Re: Stainless = speed?

I've been playing around with propellers all summer and if I've learned anything, it is that it is very hard to predict anything exactly.<br /><br />In general, there are some models of props that are sharper than others, but don't expect any dramatic differences.<br /><br />It seems to be hard to compare across brands and models of props and, in the end, you've just got to try some out on your specific boat.

 

[shep70057]

Re: Stainless = speed?

Something else to note is that stainless isn't going to flex as much as aluminum. If you go with the same style pitch stainless prop, you will "more than likely" loose some r's.

 

[Dhadley]

Re: Stainless = speed?

Exactly Shep. A given ss prop of the same design as an aluminum will have less slip. Therefore it will be more efficient. CJ, the difference will show up in the final slip %.<br /><br />IE -- <br />ss should = more efficient<br />more efficient should = less slip<br />less slip should = more speed

 

[LubeDude]

Re: Stainless = speed?

Sounds to me that you need to stay with the same pitch you now have with the stainless. I think that a 21P is gonna kill ya all the way around.

 

[crackerjack]

Re: Stainless = speed?

I'm okay with a top end of 40 mph from my VIP 184 with 3.0 mercruiser, but...<br /><br />Stingray has been advertising that their 185 with the same engine/drive has a top end of 49mph! That's a huuuuge difference.<br /> http://www.stingrayboats.com/products/models05/power_options.html <br />Their chart shows that they run 21p aluminum, and their boat is about 150 lbs lighter than mine and they have their "patented" hull design. But really I don't understand such a big difference in top end. It's even verified by independant sources...

 

[TilliamWe]

Re: Stainless = speed?

cj, it's all in the hull. Stingrays are fast for their size/power.<br /><br />you need 19pitch stainless, but don't count on a huge speed increase.<br /><br />you ever read trailer boats mag? July 2005 issue will help you.

 

[Dhadley]

Re: Stainless = speed?

I used to have 2 15' boats. One was an Allison and one was a Tahiti / Rally Sport copy. We ran the exact same V4 on each. The Tahiti / RS would run abut 50 or so. The Allison ran about 75.<br /><br />Quoting TW; It's all in the hull design baby.<br /><br />With an I/O youre more or less stuck with the X dimension you have unless you want to go down. Even if your height and theirs is the same (and their claims are true) the hull design has everything to do with it.<br /><br />Something like the Stiletto 19 ss should bring the r's down just a tad so youre right at 4800 and maybe pick up a tiny bit of mph.

 

[--GQ--]

Re: Stainless = speed?

crackerjack, a stingray is smaller than other boats in the catogory. i have a chaparral with the same engine but 8 inch wider and a bigger gas tank. it does 45 at 4800 rpm. SIZE DOES MATTER.

 

[Richard Petersen]

Re: Stainless = speed?

And my Chaparral 186 with a 5.0L 220hp does 56 alone. Speed is very expensive.

 

[Richard Petersen]

Re: Stainless = speed?

 

[--GQ--]

Re: Stainless = speed?