15 HP Merc SS 9.25 x 11 prop help

[Fr3AkAzOiD]

Looking for a SS prop for my 2000 2 stroke 15 HP Mercury Outboard (8 spline).
I'm looking to improve my top speed by a couple mph.

Already know I want to go with an 9.25 x 11 pitch as I currently have a 9 pitch alum and was able to run a 10 pitch power tech SS for a day last summer. Results were improved but not as good as I had hoped they would have been.

So far I have only found 2 props and would like to know if anyone has any experience with either of them or could recomend another better prop.

Power Tech model: SWA3R

and

Solas model: Saturn-3




Thanks in advance for any input.

 

[Mi duckdown]

Re: 15 HP Merc SS 9.25 x 11 prop help

Spending alot of money on a 15hp for a couple mph. Do you have a tach on this motor?

 

[steelespike]

Re: 15 HP Merc SS 9.25 x 11 prop help

Do you have all the performance info information from the 10" prop.wot rpm and speed.
There is a lot of knowledge here and we can determine if your performance with the 10" prop was up to par.
Have you refined your motor setup?An arbitrary pitch increase could be detrimemtal to the motor if it takes it below its rpm range.
I don't have much info on the power tech.
The Solas props in general have a good reputation for price and performasnce.
Its difficult to give an informed opinion on a prop for your application when we don't have any boat info or performance numbers.

 

[Fr3AkAzOiD]

Re: 15 HP Merc SS 9.25 x 11 prop help

Spending alot of money on a 15hp for a couple mph. Do you have a tach on this motor?

Stuck with the 15 hp so I'm doing what I can with it. I have a Tiny Tach.

Do you have all the performance info information from the 10" prop.wot rpm and speed.
There is a lot of knowledge here and we can determine if your performance with the 10" prop was up to par.
Have you refined your motor setup?An arbitrary pitch increase could be detrimemtal to the motor if it takes it below its rpm range.
I don't have much info on the power tech.
The Solas props in general have a good reputation for price and performasnce.
Its difficult to give an informed opinion on a prop for your application when we don't have any boat info or performance numbers.

I have a 10.5 ft Mercury Watermouse.
My alum 9 pitch is a little rough around the edges but not in terrible shape overall. However it does rev over the 5,000 - 6,000 that the motor is set to run in. Last time I ran it with the 9 x 9 alum it was around 75 degrees and revving 6,075. Though it does rev around 5,950 with it's 100+ F out. Top speed is 23/24 mph gps verified.

The 9.25 x 10 pitch I ran for a day was turning around 5,800 but I believe the fact that the prop has a better design and doesn't have the rough edges my 9 pitch has had something to do with it. I was also able to raise the motor one more hole with the 10 pitch SS without cavitation.
My results from that were a gain of around 3 mph in top speed and only a slight increase of time to get on plane. Top speed 26/27 mph gps verified.

Now this motor is from 2000. The boat it is on was a rental for a number of years. I know this will be another post later on but I do plan to Seafoam the engine to get rid of built up carbon and hopefully smooth out the idle. I also plan on rebuilding the carb if need be and make sure the timing is set correctly.
Maybe I'm being optimistic but I think I'll be able to free up some power that has been lost over the years, even if it's only by 1/2 a horse.

I'd think of throwing on a 25 hp Merc but my little boat is only rated for 15 hp and going from having 75 lbs up to 115 lbs hanging off the back worries me. Especially considering the whole boat including the transom is just PVC.
Not to mention I can think of a better why to spend the $1,500 it would cost for a new motor.

 

[steelespike]

Re: 15 HP Merc SS 9.25 x 11 prop help

Your setup is surely working really well.Prop calculator says about 5% slip at 26 mph. very good.
Calculator says 11" at 5600 would be about 27.7.
thats assuming same slip and rpm loss per inch.
By the way it's ventilation you experience when the prop loses its grip.Cavitation you don't feel.
You should raise the motor to a point just before you get venting.
May not gain much. Of course your hole shot will be a little slower with the 11.
Hopefully it won't push the hole shot over the edge.

 

[Fr3AkAzOiD]

Re: 15 HP Merc SS 9.25 x 11 prop help

Ventilation/Cavitation.....I knew it was one of the ...ations.

I knew what size I needed but just wasn't sure about the brand prop.
There is about a $100 difference between the Solas and the Power Tech and though more money doesn't always mean better product I was wondering what could account for that $100 difference.

 

[steelespike]

Re: 15 HP Merc SS 9.25 x 11 prop help

The sw is a semi weedless. And describes as not loading the motor as much.
With wanting more speed it would seem a SRA3 would be a better choice.
PTPROPELLER.com has descriptions of the powertech.
The Solas is imported.

 

[steelespike]

Re: 15 HP Merc SS 9.25 x 11 prop help

Ventilation/Cavitation.....I knew it was one of the ...ations.

I knew what size I needed but just wasn't sure about the brand prop.
There is about a $100 difference between the Solas and the Power Tech and though more money doesn't always mean better product I was wondering what could account for that $100 difference.

Don't feel bad I have a couple of old factory owners manuals that refer to vantilation as cavitation.
Cavitation usually occurs on the back of the blades and can errode the surface of the prop.
You don't feel anything.
Sometimes can cause damage.Cavitation can be an indication a prop is working really well.

 

[Fr3AkAzOiD]

Re: 15 HP Merc SS 9.25 x 11 prop help

The SRA3 is a 10 inch prop and the SWA3R is a 9.25 inch.
I'd have to check if it would fit but other then that what effects would the extra 3/4 an inch do?

EDIT: Wouldn't that larger diameter (even if only slightly bigger) reduce ventalation and prop slip on the low end but add drag and cost top end speed?

 

[steelespike]

Re: 15 HP Merc SS 9.25 x 11 prop help

Diameter is usually a secondary consideration. If its listed for your boat it should fit.
An 11" prop should perform like an 11" prop.
I don't pretend to fully nunderstand prop design but a semi weedless that is described as not loading the motor as much
doesn't seem like it would produce the most speed.
I think the SR would have better slip numbers. It is raked and cupped both terms you see describing
props intended for speed.
Do you know what the actual model the 10" you tried was? If the 10 wasn't raked or cupped then the SR
will surely run differently.Its even possible that it may do better in a 10" pitch than the one you tested.It does appear they will exchange props based on your results."for a nominal fee"