4 blade propeller on stringer 400

[M0bi0us0ne]

Hi,
I have a 5.5m boat with a 3.0L and a stringer 400, with a 3 bladed 13.5x15 prop. Last year I started taking tourist around the lakes for tours. Top speed is not my priority, fuel efficiency is. Will a 4 bladed prop help on that front? My understanding is that a 4 bladed prop will allow me to get on plane faster and at lower rpm therefore saving fuel. Any thoughts and pitch recommendations?
Thanks

 

[alldodge]

Fuel usage is based on HP needed. Fuel usage calculation is between 0.45 to 0.50 pounds of fuel per hour

You have a 5.5M (18ft) boat with a 3.0L and boat weight is about 2100 dry. Add fuel gear and people is all variable. Find the prop that with max load you can reach WOT of 4800 rpm and that is the prop you should use

Having a higher pitch prop only causes motor to lug getting on plane

Have a low pitch prop gets up on plane faster but can over rev. The amount of rpm is not the issue with fuel burn.

If you have a prop which the motor can over rev if going WOT is not an issue if motor is turning higher rpm's, so long as it's under max rpm. The motor only burns the amount of fuel needed to reach speed needed based on load.

In short if you use to turn 3500 rpm with basic load, and now you turn 4000 rpm this does not mean your burning more fuel

 

[M0bi0us0ne]

Fuel usage is based on HP needed. Fuel usage calculation is between 0.45 to 0.50 pounds of fuel per hour

You have a 5.5M (18ft) boat with a 3.0L and boat weight is about 2100 dry. Add fuel gear and people is all variable. Find the prop that with max load you can reach WOT of 4800 rpm and that is the prop you should use

Having a higher pitch prop only causes motor to lug getting on plane

Have a low pitch prop gets up on plane faster but can over rev. The amount of rpm is not the issue with fuel burn.

If you have a prop which the motor can over rev if going WOT is not an issue if motor is turning higher rpm's, so long as it's under max rpm. The motor only burns the amount of fuel needed to reach speed needed based on load.

In short if you use to turn 3500 rpm with basic load, and now you turn 4000 rpm this does not mean your burning more fuel

So getting on plane faster and at lower rpm won’t save fuel?

 

[matt167]

So getting on plane faster and at lower rpm won’t save fuel?

No because the engines relative load is the same. 4 blade actually puts more power into the water so to speak. They are generally used for tubing and skiing. A whale tail which is often used on rotted water logged boats for a little more performance may be slightly beneficial as they provide a little bit of stern lift. The more you get the boat out of the water, the less drag it will have. Of course the lift is tied to the speed you’re going