Inboards-Props spin inward not outward

[Luna Sea]

Just wondering, say someone rigs a boat thinking the engines are in correct, but due to the transmissiion gearing (or something to that effect), the props spin towards each other. They are "counterrotating" but instead of spinning towards the sides of the boat, they're spinning towards the centerline.<br /><br />Port motor's prop spins clockwise, in forward, and starboard prop spins counterclockwise.<br /><br />What effects will this have on the boat's handling/performance?<br /><br />Thanks in advance.

 

[TwoBallScrewBall]

Re: Inboards-Props spin inward not outward

My guess would be none. Notice the darker letters there....

 

[wally jr]

Re: Inboards-Props spin inward not outward

i just read about props some where in "iboats" prop section. they should "not" spin in the same direction. it will cuase your boat not to steer correct. it has to do with cavitation,cup,and mainly water displacement. look it up.. or i'll get bact to you

 

[wally jr]

Re: Inboards-Props spin inward not outward

Two propellers spinning the same direction on twin engine boats will create steering torque. In other words, two right-hand propellers pull the stern hard to the right and the bow to the left. <br /><br />Two opposite-direction propellers on twin engines eliminate this steering torque because the left-hand propeller balances out the right-hand propeller. This results in better straight-Line tracking and helm control at high speed. <br /><br /> here, i found it...good luck...

 

[snapperbait]

Re: Inboards-Props spin inward not outward

Depends on the boat....

 

[John Carpenter]

Re: Inboards-Props spin inward not outward

I am not sure what effect it will have, but I do think it is backwards from what would be considered a normal installation.<br /><br />Looking from behind the boat, in a normal counter-rotating setup..the port prop would turn counter clockwise in forward and the starboard prop would turn clockwise.<br /><br />Were the engines and/or transmissions removed from the boat? As a unit? Are the engines themselves counter rotating? I am sure that you don't want to pull everything...but you may need to. We need a gearhead in this thread

 

[Bondo]

Re: Inboards-Props spin inward not outward

snapperbait Already Answered this Question........<br /><br />There is No Normal installation.........<br />Every hull is Different........<br />Wether they turn In, or Out is based on the Hull design........<br />Turning In gives Slightly more stern lift.......<br />Turning Out gives Slightly better stability......

 

[WillyBWright]

Re: Inboards-Props spin inward not outward

What Bondo said. And the effect is definately slight. Might make a difference of a mph or two. Unless you have counterrotating engines, you can switch that at the shift levers. Counterrototing engines are pretty rare. Those you can't switch without changing some internals. Easier to swap motors.<br /><br />This is something you also rarely see done. You can (and probably should) switch from year to year. Kinda like rotating tires. If the trannys are always used in the same direction, only that gear is wearing in forward. If you switch annually, you'll divide the wear evenly and the tranny should last longer. Not a big job. Swap props and change the shifting at the levers.

 

[Capt Ken]

Re: Inboards-Props spin inward not outward

Outboard turning the props makes for a more stable boat. I know of no boat design that call for inboard turning props. Someone down the line has made a mistake in your boat. You don't say what make model of the boat nor engine/transmission type so its hard to guess where the problem is. If you have counter rotating engines, then someone has installed them on the wrong side. If you have newer engines with BW series 5000 transmissions, then you can reverse the direction by shifting the lever opposite the way they are now. No other transmission is able to do this. If you keep the props turning inboard, the backing of the boat will be near impossible. Just be sure the transmissions aren't turning in reverse when the boat is going forward. I've seen folks install the props on the wrong side and rather than pull the boat and change them, just reverse the shifters. Don't last very long.

 

[beezee28]

Re: Inboards-Props spin inward not outward

In twin engine configuration, each prop rotation should be counter to each other as this would make steering easier, reduce the torque too as mention earlier.

 

[rodbolt]

Re: Inboards-Props spin inward not outward

I really have not seen much difference.<br /> I work on boats that the left hand unit is on the stbd side and units that the left hand unit is on the port side.<br /> I have a few that both turn the sme direction with no issues. a friends frankenrig has twin standard rotating alpha with 3.0's that runs almost 60 with no issues.I will agree that without checking the transmission manufacturing data, dont just decide to change the direction or you will buy a clutch.<br /> good luck and keep posting