OK we all know props turning in provide stern lift and props turning out provide bow lift.

I was asked by a friend what kind of "rough" speed difference would there be in x boat turning x props with both props turning one direction 'VS' turning in, or out. I didnt have an answer.............................

Pretty sure its the opposite????????????

Spinning in gives more bow lift and spinning out gives more stern lift. I have never seen anybody report more than a couple mph increase.

So I may have had the first part flip flopped.

My friend is looking at an old Liberator that according to a lot of imput and calculations should run 55 to 60 mph. On the seatrial it only went 45 WFO.

He says the motors are good on power there just no top end speed.

It has 2 standard rotation Alphas on it, and he is wondering if that could possibly account for the lack of top end.

Spinning out is usually faster but it depends a lot on the boat...I'm not sure at those speeds that it would make a big difference. Only thing you may experience is more of a tendency to lean to one side or the other because of unbalanced torques from each drive.

What are the slip numbers? How deep are the props in the water? Really low x could do it. The drive may be deeper and "pushing" more water than it needs to be.

"Old" can also mean "wet core that has sucked up a lot of water and put on some weight." Motors may not be pushing as much hp or torque as they once did either.

Brad.

The boat he is looking at does NOT have counter-rotating drives. I am leaning towards the bottom paint and wrong props....Trying to get ahold of my buddy still......

With both drives turning the same direction you do lose some speed, having both wheel tuning the same direction rolls the boat up higher on one side also the stern is trying to walk a little to one side. The only fix is go counter rotating, a counter rotating Alpha is one weak piece they do not hold up to any hard running. When they give up they push the guts out the back of the gear case, if you what some reliability live with the traits of same rotation.

Phil

Interesting response Phil. I just put on an Alpha 1 counter rotation drive and found the boat a lot smother and easier to drive. I was going to sell my standard rotation drive but it sounds like I should keep it for backup.
I had an engine issue so I an thinking of a couple of 383 strokers but the weak drive gives me second thoughts. Thanks for the info.
PS: I didn't pick up any speed by changing but it's not a scary to drive so now I can put in more power.