Stainless prop selection

[river rat 26]

I have a 18.6 alumacraft with a 70 Yamaha and would like to run a stainless prop. It has a 13 1/2 x 15 Michigan Wheel on it now that seems about perfect. Runs 6k at about 33mph wot. Should I get the same diameter and pitch in stainless and any certain manufacturer? Kind of clueless about this. Boat is used in rivers and Bays and the aluminum props are getting beat up quick. Mtr is a 2005 2 stroke boat is a center console if this makes a difference...Thanks

 

[SkiDad]

Re: Stainless prop selection

I'm looking at powertech props myself - maybe check with them - ptprop is the website. Maybe they can get you into a 13.5x14 or 13.25x14

 

[MikDee]

Re: Stainless prop selection

You need to drop the pitch a bit, diameter will be in proportion automatically, unless you have a heavy boat, which you don't. SS props don't flex, so your speed may go up. They're a bit harder to spin, but solid thrust is there throughout the range.

 

[alldodge]

Re: Stainless prop selection

I have a 18.6 alumacraft with a 70 Yamaha and would like to run a stainless prop. It has a 13 1/2 x 15 Michigan Wheel on it now that seems about perfect. Runs 6k at about 33mph wot. Should I get the same diameter and pitch in stainless and any certain manufacturer? Kind of clueless about this. Boat is used in rivers and Bays and the aluminum props are getting beat up quick. Mtr is a 2005 2 stroke boat is a center console if this makes a difference...Thanks

Stick with what you have, going to SS will only reduce what you have now. It will look prettier when setting on the trailer

 

[jestor68]

Re: Stainless prop selection

A visit to the prop section shows a variety of SS props available for your Yamaha from Solas, Michigan, Turning Point, etc.

Any of them will be suitable, with the Solas New Saturn and Michigan Wheel Apollo having the best price point.

Since you're getting 6K rpm with your aluminum prop, I'd recommend using same pitch(15) for better performance.

Expect a slight reduction in rpm(100-200) with improved over all performance; acceleration, cruising, and top speed.

Your aluminum prop is showing 11% slip(not bad). Any of these SS props will reduce that further; possibly into the 9% range.

 

[river rat 26]

Re: Stainless prop selection

I want to go stainless for durability, possible performance enhancements always accepted. (pretty ain't my thing, you should see my boat)... jestor68, thanks seems like sound advice. Don't remember seeing any 14p's when looking at props so staying with the 15 sounds good. I'm guessing a couple of hundred rpm won't upset the Yamaha much. Thanks also for the slip calculation. When I do this I'll post the new numbers, might be of some use to someone...

 

[WIMUSKY]

Re: Stainless prop selection

You need to drop the pitch a bit, diameter will be in proportion automatically, unless you have a heavy boat, which you don't. SS props don't flex, so your speed may go up. They're a bit harder to spin, but solid thrust is there throughout the range.

I've always heard that, but never read why? Is it because of the extra weight of the SS and dropping a pitch will maintain the current rpm of the aluminum prop?

I want to go stainless for durability, possible performance enhancements always accepted. (pretty ain't my thing, you should see my boat)... jestor68, thanks seems like sound advice. Don't remember seeing any 14p's when looking at props so staying with the 15 sounds good. I'm guessing a couple of hundred rpm won't upset the Yamaha much. Thanks also for the slip calculation. When I do this I'll post the new numbers, might be of some use to someone...

Please post your results. It will help me since I'm going SS this year too. Very curious to see the difference in numbers/performance between the same pitch ss and aluminum......

 

[SkiDad]

Re: Stainless prop selection

I've always heard that, but never read why? Is it because of the extra weight of the SS and dropping a pitch will maintain the current rpm of the aluminum prop?

i tried it last year on my boat - i average 5000 rpm with my new 13.125x15 pitch AL prop... rpm dropped to 4700 with a 13.75x15 pitch stainless prop i picked up used - mid range had a little more power. But at 4700 in my case it cost me speed. I think about 200 of the rpm difference is the cupping - the other 100 is the diameter difference. So i think my educated guess is that most Aluminum props are not cupped and SST are - so that is why you need to go down a pitch to keep same rpm. I'm looking at a 13.25x14 if i can afford it this year - I think that will get me back to about 5000 rpm again. Although I must admit I don't like the clunk of the SST when i put it into gear (which happens a lot because we ski alot)

 

[WIMUSKY]

Re: Stainless prop selection

i tried it last year on my boat - i average 5000 rpm with my new 13.125x15 pitch AL prop... rpm dropped to 4700 with a 13.75x15 pitch stainless prop i picked up used - mid range had a little more power. But at 4700 in my case it cost me speed. I think about 200 of the rpm difference is the cupping - the other 100 is the diameter difference. So i think my educated guess is that most Aluminum props are not cupped and SST are - so that is why you need to go down a pitch to keep same rpm. I'm looking at a 13.25x14 if i can afford it this year - I think that will get me back to about 5000 rpm again. Although I must admit I don't like the clunk of the SST when i put it into gear (which happens a lot because we ski alot)

Thanks for the info. What about hole shot? Better? Worse? About the same? I have a 14x17 AL. SS are 13.25x17 so I would be dropping .750 dia which should help maintain rpms, I would think......

Hopefully I'm not hijacking your thread river rat and some of this info may help you...... Still want to hear your results......

 

[river rat 26]

Re: Stainless prop selection

Not at all, the more information we get the better. I ordered the Apollo from I-boats this am and will let you all know how it works out...

 

[MikDee]

Re: Stainless prop selection

Thanks for the info. What about hole shot? Better? Worse? About the same? I have a 14x17 AL. SS are 13.25x17 so I would be dropping .750 dia which should help maintain rpms, I would think......

Hopefully I'm not hijacking your thread river rat and some of this info may help you...... Still want to hear your results......

I don't think hole shot would be better due to the weight, & rigidity of the SS prop. On take off, your alum. prop flattens out some to a lesser pitch, making it better. When cruising at a continual speed, the alum prop regains it's flex to normal pitch. Stainless doesn't do either, at all speeds it is providing max. thrust. If you set the throttle at one speed the SS prop will hold it almost like cruise control regardless of water conditions.

 

[river rat 26]

Re: Stainless prop selection

Got the Apollo yesterday, installed and got it out on the lake today. I am very happy with it. I lost approximately 200 rpm and gained about one MPH. It feels like I am able to maintain plane at a lower speed than with the aluminum prop. Trim seems to work about the same, proposing happens at about the same place. One surprise to me was shifting seemed the same as with the aluminum, no clunk that I experienced with other heavy SS props. As I said before I like it and appreciate the help and advice offered by jestor68 and others.... The Apollo (Michigan Wheel) is a 13 3/8 X 15. The aluminum was 13 1/2 X 15, also a Michigan Wheel. I did have to notch about 1/8" X 1/2" out of the trim tab to clearance the new prop or I could have purchased part number 6E5-45371-10-00 (trim tab) This information was from Michigan Wheel. Of course, they do not recommend notching the trim tab.

 

[WIMUSKY]

Re: Stainless prop selection

Thanks for the update river rat! Did you notice any difference in the hole shot? I've done some research and I narrowed mine down to 2 choices. Just haven't posted up yet because my boat is still in storage and I'm not 100% on the pitch. I am 95% sure...

 

[jestor68]

Re: Stainless prop selection

Got the Apollo yesterday, installed and got it out on the lake today. I am very happy with it. I lost approximately 200 rpm and gained about one MPH. It feels like I am able to maintain plane at a lower speed than with the aluminum prop. Trim seems to work about the same, proposing happens at about the same place. One surprise to me was shifting seemed the same as with the aluminum, no clunk that I experienced with other heavy SS props. As I said before I like it and appreciate the help and advice offered by jestor68 and others.... The Apollo (Michigan Wheel) is a 13 3/8 X 15. The aluminum was 13 1/2 X 15, also a Michigan Wheel. I did have to notch about 1/8" X 1/2" out of the trim tab to clearance the new prop or I could have purchased part number 6E5-45371-10-00 (trim tab) This information was from Michigan Wheel. Of course, they do not recommend notching the trim tab.

Thanks for the follow up. A lot of the performance improvements are a "seat of the pants" feeling in terms of acceleration improvement, cruising mph/rpm, etc, without the testing equipment used by the pros.

It's good that you stuck with the same brand of prop. Often times, when changing from one brand (design) to another, the results can be interesting.

The mod to the trim tab is due to the Apollo having more rake than the aluminum prop. That's why it's often required to change trim tab anodes when switching to a SS prop. There will usually be a note there to indicate that you need to change the trim tab anode.

 

[river rat 26]

Re: Stainless prop selection

Hole shot is prolly better, yesterday was very windy and they were generating so the current was strong on the river. I was averaging my numbers between down river, down wind and heading upriver and into the wind. All in all I got a gut feeling that this prop was an all around improvement. Kind of like a 4x4 low range feeling from it, lots of control. Got up in some narrow creeks with it just to get a break from the wind, can definitely notice the difference in low speed handling. Oh and yeah, it's real Purdy...I let you know how it fishes, that's the true test.