Rotation and twin engine installation.

[harbormaster]

Regarding the prop rotation in a twin engine 31' performance boat.

I have heard that if the props rotate inboard that it will give you slightly more top in but make it difficult in docking.

If the props rotate outboard that it will reduce top in but be less difficult in docking.

Anyone heard this before?

[terry]

Scot,
yes that is correct.

[harbormaster]

Ted,
What kind of difficulty docking are we talking about?

[terry]

It is about half as responsive around the dock as outboard rotation. When 1 is in forward and the other in reverse it is not as responsive.
Its not a big deal once you get used to it.
It requires a little steering wheel action to swing to bow around.

[Cuda]

I've also heard of dangerous handling characteristics with the props spun in. I know I wouldn't chance it for a couple mph.

Oh yeah, on the Kamma's the props spin in. :rolleyes:

[terry]

I have never heard or experianced that.......

[MOP]

I have seen this bandied back and forth for many years, every major manufacturer rotates props inward. I truthfully can and will not argue the point. I know of an odd scenario locally where a not to deep pocketed buddy bought a pair of right hand diesels and put them in his old Richardson. I laughed at him till I got to run the boat, yes underway the boat would walk off to one side as soon as you let go of the wheel. But as god is my witness it was a dream to dock and I could not feel any tendency to walk off during docking. I taught boat handling professionally for 6 years, what we run are I/O's. They do not dock like fixed shaft twin screw vessels, down at the marina we have some of the best laughs at guys trying to use both engines to spin a boat in tight quarters. Think about the next statement! The main thing I taught my clients about twin I/O docking was just when you don't expect it the shift interrupter will kill an engine or just stall for no apparent reason. So when docking leave your best running engine running in neutral, that way if the other one dies there is only a split second lost putting the good one in gear and docking safely. This will eliminate damage and embarrassing moments.

[kk89z33]

The rotation from the factory, on a 1989 Z-33 was rotating outward (at the top). From reading Powerboat Magazing I have seen that outward gives the boat more stern lift, inwards will lift the bow. I never tried reversing this set-up to see how it effected the boat. Maybe this year??? Hope this helps..

[Cuda]

Here are some comments on inward rotation.

Rotation (http://www.offshoreonly.com/forums/showthread.php?s=&threadid=69213&highlight=props+spinning+in)

[Ranman]

I plan to avoid the issue by running a triple engine setup a-la Red Reynolds. Now is that two right and one left or one right and two left. Guess it doesn't matter at that stage of the game. :D

[33 Daytona]

My props spin inward per the factory setup. When I got the boat I did hear about added top end and it being harder to dock. Beings how this is my first twin engine boat I have nothing to compair it to but when I do have one prop going forward and one in reverse the boat does not spin around like I exspected but there are ways around that. Other than that I have had no handeling problems.