Rpm and top speed loss after changing reeds?

[Destroyer]

Originally Posted by jvitiel

Interesting. I never considered the cup. Thanks for the insight!

There's a lot of things that determine prop slip. Pitch, Cupping, Rake, Material, Diameter, Number of blades, Leading edge, Trailing edge, Blade tip, Blade root just to name a few.

A good quick way to determine what is your prop slip is to use this calculator from Mercury Racing. While it may not be accurate for a racing enthusiast, it's more than sufficient for the average Joe.

http://www.mercuryracing.com/prop-slip-calculator/

[spareparts]

First thing to do is go back and double check your work. Look for air leaks(spray carb cleaner while the engine is running). Check compression and spark. Look thru the intake with a light to make sure all the reeds are in good shape. You're worn out factory reeds may have been flowing more air than the new "performance reeds", We had a set of old worn out champ boat reeds that made more rpm than anything else we tried. As good as they ran, they started to crack and we threw them away before it caused engine damage. I rarely find any gains from using performance reeds on stock engines. What shaoe were you're reed blocks in? were they rubber coated?

[1224bret]

The old reeds looked fine. The blocks looked ok also they were rubber coated but didn't see anything wrong with them. Was just hoping to smooth out the idle and keeps from worrying about eating a broken reed. Will try to do some more checking and make sure there isn't any air leaks. Did a little checking this weekend and found the tps slightly below spec on the wot voltage. If I remember right when I checked it last year I was on the upper end of the ok range this time I was a few tenths of a volt below the minimum. Not sure that this would drop me 400 rpm but if I understand the way this thing works right the tps controls the timing and fuel so being just ever so slightly low may have changed the timing and fuel delivery some just not sure how much. Thanks for all the input guys I really appreciate it. I'm probably over propped some but was running at the top of the recommended rpm last year before I tore it down I will see if I can find anyone local with a 19 p I can try out or just order one used from flea bay I guess...