Prop Rotation

[jross]

After getting my new to me 283 put back together at the end of last year I was only able to get it out a handful of times. So I'm wondering what other guys with twins, either inboard or outboard, are running in or out for prop rotation. Currently I'm turning in but considering turning out for a more stable high speed passes and easier docking, so I've heard. Any input would be appreciated

 

[DropTop5.0]

I'm turning out. I tried turning in once and it looks lost speed and handling so I've been out ever since.

 

[JUPITER PULSARE]

First, lets decipher what turning in and turning out actually is:

Turning Out: Port motor turning counter clockwise with LH prop.
Starboard motor turning clockwise with RH prop.

Turning In: Port motor turning clockwise with RH prop.
Starboard motor turning counter clockwise with LH prop.

That being said, turning out will make the boat easier to handle around the docks at idle speeds, will make the stern of the boat run wetter (slower) by sucking the stern down but make it easier to lift the bow. This combo is great for a boat that is bow heavy...not so great for a boat that is light in the bow because it can create a porpoise.

Turning in will make the boat harder to handle around the docks (which can be countered by trimming the motors up a bit at slow speeds) but will lift the stern of the boat higher by placing the downward thrust of the "turning in" props closer together, thereby creating a stronger force of stern lift allowing the boat to fly higher in the water with less trim to carry the bow which, by the the laws of physics (drag & friction), creates more speed.

For the inexperienced driver, turning the props in at high speeds can be a little intimidating until you get some seat time because you'll have to learn how to "fly" the boat on the pad like a small single engine V/pad bottom boat. The boat will feel lighter and flighty..BUT A BLAST TO DRIVE!!

I've done a lot of setup on my twin motor 2800SX Outboard and have tried numerous combinations of motors spinning both in and out. I can attest through trial and error that the boat runs much better turning in than turning out. Bare in mind that each time you make the change you have to swap the position of the shift cables inside the shifter box..

 

[jross]

First, lets decipher what turning in and turning out actually is:

Turning Out: Port motor turning counter clockwise with LH prop.
Starboard motor turning clockwise with RH prop.

Turning In: Port motor turning clockwise with RH prop.
Starboard motor turning counter clockwise with LH prop.

That being said, turning out will make the boat easier to handle around the docks at idle speeds, will make the stern of the boat run wetter (slower) by sucking the stern down but make it easier to lift the bow. This combo is great for a boat that is bow heavy...not so great for a boat that is light in the bow because it can create a porpoise.

Turning in will make the boat harder to handle around the docks (which can be countered by trimming the motors up a bit at slow speeds) but will lift the stern of the boat higher by placing the downward thrust of the "turning in" props closer together, thereby creating a stronger force of stern lift allowing the boat to fly higher in the water with less trim to carry the bow which, by the the laws of physics (drag & friction), creates more speed.

For the inexperienced driver, turning the props in at high speeds can be a little intimidating until you get some seat time because you'll have to learn how to "fly" the boat on the pad like a small single engine V/pad bottom boat. The boat will feel lighter and flighty..BUT A BLAST TO DRIVE!!

I've done a lot of setup on my twin motor 2800SX Outboard and have tried numerous combinations of motors spinning both in and out. I can attest through trial and error that the boat runs much better turning in than turning out. Bare in mind that each time you make the change you have to swap the position of the shift cables inside the shifter box..

That's a lot of great info! Thanks for the response. With the two big blocks it definitely is stern heavy. I think I'm going to leave them turning in and hopefully with more seat time this year get used to it at high speeds.

 

[Mink]

In too win...

 

[ezstriper]

looks like the only boats that liked the turning in are fountains, most others were iffy

 

[Gimme Fuel]

looks like the only boats that liked the turning in are fountains, most others were iffy

My powerquest likes turning 30p Bravo I's in. Could be a stepped-hull thing though.

When switching between turning in and turning out, the lift characteristics change pretty drastically and might actually precipitate a change in propeller style. If your boat likes a stern-lifting prop when turning OUT, it may provide too much stern lift when turning IN. Typically a pad-bottom boat won't like a ton of stern lift because it flattens out the hull's angle of attack therefore increasing wetted area and not allowing the bow to rise enough for the pad to work properly. On the other hand something big and heavy with a straight v-bottom like an old Cig that lacks lifting strakes towards the rear can benefit from stern lift.

 

[check253]

looks like the only boats that liked the turning in are fountains, most others were iffy

The 43 responds better turning in. There seems to be some confusion about what each does. Turning in induces more bow lift while turning out induces stern lift.

 

[JUPITER PULSARE]

The 43 responds better turning in. There seems to be some confusion about what each does. Turning in induces more bow lift while turning out induces stern lift.

It's how you comprehend the hydrodynamics. Turning in creates a more focused downward thrust thereby lifting the stern of the boat higher in the water which allows you to trim the motors higher creating more bow lift. The physics created by the additional lift in the stern and less wetted keel in the middle/bow area induces more speed, less friction and frees up the hull. This "freeness" makes the boat more challenging to drive (fun in my world)!