Prop (Ron Hill) questions...

[Joakim]

What is the good or bad for this propeller on a offshore boat.

On a e-tec 150 H.O? With lift... and nose cone.

And how to calculate size ?

[odyssey aka Blue streak]

The other guy's may be able to put me straight but my first impressions are that unless the evinrude 150 ho has a offshore leg or an above water exhaust etc it will just cavitate on the exhaust gases exiting around and infront of the prop.
My understanding is that a clever or chopper with out a through hub requires a offshore leg (above water exhaust) or it will just cavitate in the exhaust gas.

You can get clever and choper props with through hub exhausts but have not seen many.

Hope thats of some help but others may be able to shed some more light on the situation or tell me im just talking bull*cks LOL

[Joakim]

Thanks.

Do you think it will be the same even if i lift the engine maximum? Do you mean all the time or in slower speed only...

The engine on the pic is on a 115 H.O and a offshoreboat...

[odyssey aka Blue streak]

I may be completly up the wrong tree but i would imagine that if the prop is a normal type clever / chopper which is not a through hub type then even at high speeds etc the exhaust gases are exiting in front of the prop creating an air pocket infront of the blades which is going to cause cavitation as there will be no water for the prop to grip on. i would be suprised if it even got on the plane.

Again i may be completly wrong.

Some one tell me if i am right or not.

[still no worries]

dont ask just test it, it may suit the way your boat it set up!

[larby]

Originally Posted by odyssey aka Blue streak

I may be completly up the wrong tree but i would imagine that if the prop is a normal type clever / chopper which is not a through hub type then even at high speeds etc the exhaust gases are exiting in front of the prop creating an air pocket infront of the blades which is going to cause cavitation as there will be no water for the prop to grip on. i would be suprised if it even got on the plane.

Again i may be completly wrong.

Some one tell me if i am right or not.

Kinda... It should make no difference once up to speed as the exhaust gases will just exit in a straight line leaving the main blade clear for the water. Even an offshore leg still exits some gas through the prop, though not much, as the water could not 'fold in' over the trailing edge of the gearbox to get to that inner part of the blade. I have run 'over hub' cleavers on non offshore legs with great success before.
It is true to say that if he is used to using through hub props he may find it slightly harder than usual to get on the plane through the aeration caused as there will be a lot of exhaust gases going over the prop. Don't be scared to rev it hard to get over the hump, you'll learn to feather the throttle just right to pop it up on the plane. In the low torque xr2 days this used to help the motors spin up to decent revs before the prop bit to the guys could run the high pitch props required for top speed.
As someone else said, just give it a shot and see what happens. Prop selection is a black art, what works on one boat may not even work on another seemingly identical boat. With a 150HO he should get up and go just fine unless the boat is particularly heavy.

Hope that helps,

James