Prop Pitch & Diameter

[peterb]

Currently, I have twin 2000 200 HP Yamaha OX66's on a full flotation bracket to push my 23' SeaCraft. I am going to do three things to improve the ride and performance.

First, I am going to fix my trim tabs. Just pulled the boat out of the water and verified that they are not functioning.

Second, I am going to raise my engines 2 holes (same as 2 inches) so that the captivation plates sit 2 inches above the keel. Remember that the engines are on a 2 foot wide bracket.

Lastly, currently, I have 3 blade counter rotating stainless steel prop's. They have a pitch of 21" (not 12" as my good friend Capt. Brain pointed out) and a 14 7/8" diameter.

During the sea trial in early March the surveyor told me to go to a smaller pitch prop. I have been reading other threads which suggest that Ishould do this as well.

Here is my question.

Can I go from a 21" pitch & 14 7/8" diameter prop to a 19" pitch & 15.25" diameter prop? Or am I better off going with a 19 & 14 7/8 prop? I am asking because I know where I can get a great deal on two counter rotating 19 & 15.25 prop's (but I also want to do the right thing here).

Any input would be greatly appreciated.

Thanks,

Peter

[Fr. Frank]

Going to the "great deal" props with 2" less pitch, but 3/8" greater diameter should be similar to same diameter, but only 1" less pitch. You should gain an extra 100-200 max rpms, roughly speaking. But then blade shape, rake and progression all play a role as well. Try it and see.

[peterb]

Thanks Padre,

They are cheap enough to try and resell if they don't work out (or so I hope)

Peter