Hey gangA prop question. My boat...

[Takin_Bets]

Hey gang

A prop question. My boat calls for an 18in x 21.5 pitch for port, an 18in x 21 for starboard per my parts manual. 

Does the .5 difference in pitch make a difference in performance or RPM's?  

[wingless]

That spec is probably close enough.

When I yank my boat I have my props retuned to Class S.

The first time I reached that level it was expensive, now it is acceptable cost.

The first time I got the Class S tune I noticed a smoothness and performance increase, greater top end velocity.

The pitch on both props is almost identical, port 21.998, starboard 21.980.

Matching RPM underway is easy using the center null gauge.

[Takin_Bets]

Hey Wingless, yes, I get how to match the RPM'S thru the gauges, but the throttles do not line up even now. I have talked to several prop companies that believe it is due to the pitch being not right. Do you have any ideas? Thanks - Paul

[wingless]

Have the props been tuned?

What do the results show?

Mine are tuned every few years and are always identical.

My throttle levers during operation are always virtually aligned.

[Takin_Bets]

As far as tuning them I am not sure but they are brand new, a matched pair except for the pitch. The throttles were fine until the props were replaced with a different pitch to starboard

[wingless]

When I examine the part manual for a 2000 340DA w/ 454 MAG MPI Horizon vee drive engines the spec is 17"x17"x1.5" RH/LH, 17"x16"x1.5" for the standard 7.4L

Stern drive gets 15.5"x17" props.

No where did I find 18"x21" props listed for a 340DA.

Regardless, even w/ new props, a good starting point is to have them tuned / balanced. It should improve the operation and top end. In my case the first time bringing to the highest tune, Class S was the most painful. Periodic tweaks were acceptable cost.

[wingless]

Also, the symptom about throttle position changing w/ new props, also having a specified pitch difference (even though small) points to that being the first thing to check.