Thanks Matt,
I'll gather as much data as I can when I run it with the new power and go from there.

Randy,
You are correct about the boat being very stable in the 90-109 mph range with the 16 x 33's. I really didn't get enough seat time in it to fully "figure out" how to run it...or dock it. Those props spinning in were tricky around the docks!! There is nothing like running a boat with twin 1200's, dry exhaust and a flashy paint job until everyone is watching and you look like a 12 year old trying to park for the first time!!

With the new engines, I'll be turning the props out...but still running the dry Stellings

No, I have IIIs with 800SC...

Good advice i was given for docking....Dock it like a single engine & use the inboard {dockside} engine...seems to work pretty well

Old School,

I know I'm getting into this conversation late. I was out of town for the Holidays. I love working with these types of situations.

Working with #6 drive propellers can be tricky but the options you have are also largely diverse. As Matt stated, there are many different issues to consider when working with #6's.

You kind of answered your own question when you mentioned the fact that the boat handled great with the 33's. If you are only decreasing HP, keep the same diameter and decrease the pitch! The boat will be the same old boat but a little slower. Now that being said, it depends on the history of the props in question. By that I mean do they match on a basic geometry level? We would need to measure that.

OK, now we are talking about changing rotation. Everything changes from here as far as our original handling base line is concerned. Yes, your docking will improve. Every other characteristic will also change. From planing to trim characteristics will be different.

Do what you said, test, take notes, retest and we can talk some more.

To answer the original question.................................
changing diameter changes "many" things...................
depending on the boat, too many to list........possibly.

Best advice, use as much diameter as the boat will "allow" you to use!

If you would like, call us anytime and we can go deeper into the subject.

Use as much diameter as the boat can handle? Can you expand on this?

here's a old one brought back to life.

My diameter is more blades area. This means better efficiancy, cruise and top speed due to more water being moved.

However, adding diameter decreases rpm and increases stern lift. If your boat becomes negatively affected by these changes, reducing diameter is required.

Therefore, use as much diameter as the boat allows you to.