Outboard prop pitch

Gary M · Post by **Gary M** » Nov 28th, '06, 20:41

I'm sure many of you outboard users have tried to match your prop with your boat.

One of the first things I noticed on my CD22 after taking possession is the outboard pushed it along fairly well while barely above idle.

Then I noticed that when I backed out of my slip and shifted to forward the motor seemed to take longer then expected to slow the boat, and if I gave it more throttle it seemed to be slipping in the water.

I have determined that I have the standard #8 prop (200X200). The one recommended for "heavy boats" is a #7 (200X178). My dealer says they now make a #6 and recommends it because he said I will notice very little changing to the #7.

He also said something about a rubber part that may be wearing out causing the prop shaft to slip.

So of course I'll go to the one place in the world where I know I can count on good advice before I just have at it!

What do you think?

Thanks
Gary

S/V Necessity · Post by **S/V Necessity** » Nov 28th, '06, 21:42

I've had the rubber piece in a prop fail and it definitly could be part of what you are describe. Behaved much the same. I ended up wanting a different pitch prop (much like you) and so I just bought another prop. But I was quoted about $40 to repair the old one.

Tod Mills · Post by **Tod Mills** » Nov 28th, '06, 21:44

...which weighs 1600# and has an almost 16' waterline length. The one which came with the motor, 200x190, and the optional one, 200x170. I am of the opinion that the 200x170 is a better match, but that even slightly lower would be even better, so that hull speed is achieved higher in the throttle range. With the original prop, the boat reached hull speed very low in the throttle, maybe fast idle or a bit above. With the lower pitch, it is more like half-throttle.....

I can't address the "rubber part" issue.

Dan & Pat · Post by **Dan & Pat** » Nov 29th, '06, 09:20

IMHO you want the rpms of the motor to be doing the work. More rpms = more work. A motor that moves you at hull speed just above idle doesn't give you much help when you need sloooow speed for maneuvering. Additionally, you will get a longer lifespan out of a motor that does its work in the range of higher rpms.

Given a choice of pitches, I'd go with the smaller number, or a flatter pitch, thus making the motor work less hard at lower rpms but putting the HP and Torque to work in the mid-range revs.

Gary M · Post by **Gary M** » Nov 29th, '06, 20:14

Well, its probably a little bit of guess work but I decided to order the #6 prop which is 200X156.

I should get it in about a week and I'll try it out the first chance I get.

The motor will go in for service in a couple of months and they can check everything out at that time but I'm convinced the standard prop is the wrong pitch for a displacement hull.

We'll see what happens. Thanks to all for the help.

Gary

Gary M · Post by **Gary M** » Dec 13th, '06, 21:02

For those that are interested, my #6 prop came in today and I had time before dark to get it installed and take the boat out for a few minutes.

I'm very satisfied so far. The problem backing out of my slip then shifting to forward is gone. No slip, the motor stops backward momentum quickly and starts forward quickly.

Now I achieve hull speed at more like 1/3 to 1/2 throttle instead of barely over idle.

So far so good. I like it!

Gary

The Cape Dory Board

Outboard prop pitch

Outboard prop pitch

prop slip.

I have two props for my boat

rpm's and torque

Just ordered a #6 Prop

#6 Prop delivered