propeller pitch selection question

[bucktail]

Hy guys

 

Cant for the life of me remember how the pitch number represents on a propeller.

Is the smaller number the less a propeller will move ie: 11 pitch moves 11 inches thru the water as opposed to a 15 pitch moves 15 inches in one revolution?

 

Thus a smaller pitch number would slow your top end down?

 

Any help would be appreciated.

 

Darren

[mercman]

YES

[danbouck]

smaller pitch = lower top end and better hole shot

[bucktail]

Would that also result in a slower troll?

[scugpg]

smaller pitch = lower top end and better hole shot

 

Unless you aren't hitting the optimal RPM range sometimes a smaller pitch will give you more top end. 1 step down in pitch usually increases the RPM by 200.

 

These guys and mercury have a good wizard to get you started http://www.turningpointpropellers.com/

[Bernie]

The optimum propeller is the one that allows your engine to run in it's recommended RPM range.

Too large of a propeller will put a strain on rod and crank bearings. It may not immediately show but will certainly reduce engine life.

Too small a pitch and the engine could over rev.

 

Here's an analogy;

Ride a 10 speed bicycle in 10th gear (big pitch prop)going up a hill, your knees are a piston rod.

Your knees are bearing lots of torque trying to pedal. Try a lower gear and it becomes easier to pedal and your knees are under less strain. You may even go a little faster because it puts your strength into the proper zone (remember the engine torque charts?).

 

Bigger isn't always better. Use the proper pitch.

[whitbyboatguy]

I would not say that that is a good guide....it used to be a good guide. Last time I used it it kept recommending I buy the SS version with no option to get an aluminum.

 

Your engine manufacturer likely has a chart available that states what propellers will give you what speed at a given weight range.

diameter also plays a part.

 

Yes, lower pitch = more torque at the low end and lower speed at the top.

 

Getting a lower pitch to slow your troll is not worth the trade off in top end IMO when compared to other ways such as throwing out trolling bags or using a trolling plate. But if one does not care about how fast they are going then sure, why not change it for better low end trolling speed.

 

 

wbg

Hey if you buy a lot of props from the sandy cove auction I might be interested in one....