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  Prop. for 13 Sport, Merc. 40 Classic

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Author Topic:   Prop. for 13 Sport, Merc. 40 Classic
RonCT posted 09-09-2003 09:19 AM ET (US)   Profile for RonCT   Send Email to RonCT  
Sorry if this is a repeat of another similar post...

I have a 2002 Sport 13 with the 2-stroke 40 Mercury. The boat performs wonderfully. What I would like to do is change the propeller to have more hole-shot for water sports at the expense of top-end. Right now I reach 33 (gps) with 2 people in the boat - impressive top speed. In my waters, there may only be 10 days a year that speed can be achieved due to chop. So, if it would cost me 5 MPH on top to get more bite, I'd do it.

If I stay with Mercury, it appears I can go with the standard black painted aluminum, the 3-blade SS Vengeance or the 4-blade SS Trophy Sport.

Does anyone have an opinion on SS vs. Aluminum, what size I might try, etc.?

Email is fine at ronjaneczko@sbcglobal.net

Thanks!

Seattlerocket posted 09-09-2003 10:46 AM ET (US)     Profile for Seattlerocket  Send Email to Seattlerocket     
I have the same boat and would like to the responses too.
Moe posted 09-09-2003 12:19 PM ET (US)     Profile for Moe  Send Email to Moe     
What's important is that the prop won't let the engine exceed the maximum rpm at wide-open throttle (WOT) with a light load, i.e. one person seated toward the center of the boat, minimal cargo, and maybe half a tank of gas, trimmed out for maximum rpm on smooth water, even if you don't normally operate it that way.

As a starting point, you need to know the maximum rpm the engine achieves with the current prop under the above conditions, and report it here, along with the prop dimensions.

--
Moe

RonCT posted 09-12-2003 11:18 AM ET (US)     Profile for RonCT  Send Email to RonCT     
I have some room to move - in theory, I could reduce pitch 1 to 2 inches.

But, if I did that, would I get better hole-shot or just more top end?

The prop that came on my Sport 13 is 10 3/8 x 14. Mercury makes the Trophy Sport in 10 5/8 x 14. I understand that just changing to a 4-blade (the Trophy), you will reduce RPMs by 50 to 100.

Again, it's low-end performance I'm after, not top end. I just can't find an answer to the question of how to improve bite. I suppose part of it is 4-blades...

Dr T posted 09-12-2003 11:37 PM ET (US)     Profile for Dr T  Send Email to Dr T     
Reducing the pitch will allow the engine to spin faster since there is less resistance on the prop. This will (usually) lower the top end, but you stand the risk of over-reving your engine. But it will give you a better holeshot.

Some time ago, I posted a thread in this forum that gave comparative prop performance of an 82 35 hp. Johnson on this hull in some extreme conditions if you are interested in what happens on an engine that is limited on torque.

tds

Dr T posted 09-13-2003 11:32 AM ET (US)     Profile for Dr T  Send Email to Dr T     
See http://continuouswave.com/ubb/Forum4/HTML/000482.html
Moe posted 09-16-2003 11:39 AM ET (US)     Profile for Moe  Send Email to Moe     
quote:
I have some room to move - in theory, I could reduce pitch 1 to 2 inches.

How do you figure that? In another thread, you provided the info needed here, and said,

quote:
I have a 2002 Sport 13 w/ 40 Classic. Used 2 seasons - very strong performance. I hit 5500 RPM and 33 MPH with original 14" pitch aluminum prop. Engine is mounted on the lowest position and I trim it up to get to Maximum. This is how it came from the dealer / factory.

Sounds like you're already hitting the motor's redline and don't have any room to reduce pitch at all without potentially overspeeding the motor.

--
Moe

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