Alum to SS What Pitch?

[trswenson]

1998 Reinell 230, 5.7L Volvo-Penta GS (carbed) 280 HP from Factory at Sea Level. 23' Long 8'6" Beam, Boat is 4000lbs dry (+/- 200). Usual load with fuel, folks, and toys including boat is 5500-6000lbs. I run at 3500' elevation on the low and 6000' high. Mostly at 4500'. I've ben asked the gear ration and still don't know it. WOT is 4200-4600(block placard).
Running a Solas 4 blade 15P prop. Actually works quite well. Can get right at 4200 WOT in perfect water conditions, with medium load (1000lbs).
90% of running time is pulling (around 3000-3500 rpms). Light load is my wife on the wakeboard at 120lbs. Heavy is 3 tubes with 5-7 people on them (750-1000 lbs).

So, I want to upgrade to Stainless steel. I want to stick with a 4blade. A 16P maybe? But reading a bunch of forums think I'm wrong in going up 1P? Will a 15P SS perform like my Aluminum with a little better top end? What about hole shot and holding in hard turns with 3 tubes behind me?

Sorry so long, couldn't find the specific answers on the other threads. thx... T.R.

 

[junior1113]

Re: Alum to SS What Pitch?

i welcome to iboats f you got that same prop in ss you would pickup 50 wot rpms if you went with a13 p 4 blade ss you would pick up about 400 i would look for a hard to find 13 0r 14 if it was my boat better to be in the upper limits of recomended range

 

[trswenson]

Re: Alum to SS What Pitch?

thanx 4 the reply !
In Pick-up do you mean gain? Nearly all the threads I read prior to posting list a loss of RPM with SS compared to alum in the same pitch. I assumed it was due to prop weight increased and lack of Flex. ummm?
I also read that WOT should be adjusted down 100 RPM's for every 1000' elevation gain. So at 4200 rpm's and 4500 feet I'm at my max WOT based on elevation.
Guess I'm thinking out loud... Please comment

14P 4 blade SS...hmmm? that's a possibility, I'd have some serious torque when pulling for sure! thx again

 

[junior1113]

Re: Alum to SS What Pitch?

ss props are thinner, make for a thiner slice through the water which allows it to spin a little faster and there USSUALLY smaller in diamiter 14p might be hard to find but if all else fails maybee get a 13 try it and if dont like have it pitched up to 14 by a prop shop if you get a ss with a lot of cup in the blade you MAY lose a little rpm. if you went prop for prop identical all. vs ss ss will spin more rpms not much but it will

 

[Tail_Gunner]

Re: Alum to SS What Pitch?

15p 4 blade at 4200 is the reference point..The target is 4600

15p 4blade ss drops to 4000
14p@4200
13p@4400
12p@4600

Check your tach for accuracy....check your timing and engine's state of tune...check your hull for growth.

When you prop for the top rpm band you are relieveing your motor from strain and better overall performance....

 

[trswenson]

Re: Alum to SS What Pitch?

Mr Gunner,

Copy that on the pitch by RPM. So 1 final question, What about adjusting for elevation? Where do I prop for WOT at? The lowest or highest elevation I run the boat at? There's nearly 4000' difference, or do I go with where I'm at the most which is closer to the lower elevation but still 1500' above it.

Check Hull for Growth? What is that? Aquatics or something?

thx......

 

[Tail_Gunner]

Re: Alum to SS What Pitch?

Mr Gunner,

Copy that on the pitch by RPM. So 1 final question, What about adjusting for elevation? Where do I prop for WOT at? The lowest or highest elevation I run the boat at? There's nearly 4000' difference, or do I go with where I'm at the most which is closer to the lower elevation but still 1500' above it.

Check Hull for Growth? What is that? Aquatics or something?

thx......

That a question for the guy's in the motor section...I really have no experience with different evaltions and its effect on perfromance. I am sure they can give you some ideal where elevaton begins to effect performance and adjust accordingly.


I take it your a fresh water boater...or trailer you boat ya think.. anyway growth can occur on a hull causing drag and some people are not aware of that. Check you tach for accuracy and if it is prop accordingly..(boat tach's are famous for being off)

 

[junior1113]

Re: Alum to SS What Pitch?

15p 4 blade at 4200 is the reference point..The target is 4600

15p 4blade ss drops to 4000
14p@4200
13p@4400
12p@4600

Check your tach for accuracy....check your timing and engine's state of tune...check your hull for growth.

When you prop for the top rpm band you are relieveing your motor from strain and better overall performance....

u might have more posts on this website but i've owned over a dozen boats and ss always spun me more rpms than alluminum unless adding cup and 200 wot rpms per 1 inch pitch is more like 150. whats next u going to tell this guy im lying about ss being thinner than alluminum i would go 13 4blade if it was mine and i would set wot rpm to which elevation u boat most this guy is just replying to grt his rank upgraded good luck

 

[hwsiii]

Re: Alum to SS What Pitch?

TR, what I found for your gear ratio is 1.78 to 1, I do not know if this is correct or not, but if it is when you change from a 15" pitch prop to a 12" pitch you will gain about 800 RPM in the same make and model of prop. As Pitch gets lower the higher there is a change in the RPM, this is a mathematical formula. I know nothing about motors and elevation so I can't discuss changing altitudes, the most I know is that as you get higher the less power you have.

Prop Change

H

 

[Tail_Gunner]

Re: Alum to SS What Pitch?

u might have more posts on this website but i've owned over a dozen boats and ss always spun me more rpms than alluminum unless adding cup and 200 wot rpms per 1 inch pitch is more like 150. whats next u going to tell this guy im lying about ss being thinner than alluminum i would go 13 4blade if it was mine and i would set wot rpm to which elevation u boat most this guy is just replying to grt his rank upgraded good luck

No junior i am not going to tell you anything....I try to keep my nose in I/O's. It is a very simple catagorey no motor height adjustment's..etc..etc..etc.

And i have not owned 12 boats...:redface:....Yet..


But 12 props....plz...:redface:....Maybe more...