Prop question

[bassfighter]

I own an 85 hp evinrude and the manufacturer recommend running from 4500-5500. I am using a SST prop 13 .25 x 17 " pitch on my boat and it seemed fine running at 5000RPM on top speed.

 

I need a spare prop, and can only afford aluminum made prop. Should I Use the same size or next size 13 3/4 x 15" to almost match the same RPM without having to go through trial and error on four different prop ?

 

Does any of you own the same size prop in stainless and aluminum? how much of a difference is the RPM on top speed using the same size pitch but one is SST and the other is Aluminum?

 

I am more concern at higher RPM to move from one spot to another on a lake. SKiing with faster acceleration is not a priority/important .

 

Thanks for any input

Edited June 8, 2008 by bassfighter

[2 tone z71]

what engine, 5000 RPM depending on size hp you may be lugging it,I run a 15 or 17 SST AND A 15 OR 17 aluminum depending on where im going all last yr I ran the 15 SST and could just reach my max WOT RPM settings 5750-5800 with the 17 this yr I can only could pull 5350-5500 RPM from my 115 @ 43 MPH

[bassfighter]

Should lower RPM be more efficient than higher RPM?

 

Our vehicle will run more efficient on 2500 RPM than on 3500 rpm.

[2 tone z71]

easy get a 17 aluminum

[jace]

I think you answered your own question when you said you could only afford the aluminum. Get it and be glad you have a spare handy.

[Garry2Rs]

In my area, Stoney Lake etc; it is very rocky.

Prop damage is a fact of life, and repaired aluminum props are for sale at many marinas.

If money is tight, you can get a repaired prop for about 2/3 of the price of a new one.

They are recupped and welded, then painted to look like new.

Repaired SS props are also available sometimes.

One of the best repair places is OPS. They're at the Selwyn Rd. stop light, between Lakefield and Buckhorn,

on #23 aka the Buckhorn Road...705-652-0227

[JorgeCarlos]

what is better or difference beetween aluminum and stainless prop,

on a 4.3 mercruise i/o ??? thanks

[2 tone z71]

on any giving engine outboard or I/O the stainless will always be more effecient no slip,no give max performance,better hole shot,top end,and up here on Georgian Bay when the bow dives in to a 4-6 ft wave it dont lug the engine it has the strength to maintain its rpm

[bassfighter]

Thanks for the feedback.

 

I was assuming if I go down with 15 pitch Aluminum, the Rpm might go up and reach close to 5500 RPM on full trottle.

 

However, I am not sure if higher RPM means more fuel efficient.

 

 

I normally do not run my engine that high on full speed, I just want to make sure that the prop size is right for my application.

[POLLIWOGG]

I think the change in pitch would give you another 400 rpm and the change to aluminum would give bump it up a little more putting you close if not over your wot limit. I'd stay with the 17.