Prop recommendation for a 18" bowrider?

[Photographer]

I have a 18" Wellcraft 180 Sportsman with a 115HP Yamaha. My current prop is a 13 1/4 - 17. I would prefer better mpg than power. I use the boat with my kids cruising around.

Should I change it to a 19 pitch prop?

 

[TheOrs]

Maybe?

You are prop'd correctly when, at Wide Open throttle (WOT), the engine is turning at about it's maximum rpm (in forward gear, moving through the water obviously). You need to find out the maximum allowable rpm for your engine and then go drive the boat to see if it gets there. RPM too high you need a bigger pitch prop; too low you need a lower pitch prop. The difference is about 200rpm/inch.

If your current prop is below the max engine rpm then you will probably not gain anything in terms of fuel economy by going to a 19" as you will use more fuel to accelerate. If you are over-revving slightly at WOT then it's probably worth trying the 19" prop.

The only real way is to buy/borrow one and see.

 

[BruceK]

As above. However you may find the prop you are using now was a compromise to give you a better hole shot for water toys and skiers. Certainly with a similar sized boat I had (Sea Ray 19 footer) it ran with a 14 x 19 Ali for correct WOT revs and hole shot and 14 x21 stainless steel for best speed and economy but laboured the engine some until on the plane. The engine was a 140hp inboard but at 20 years old you could knock a big chunk of that off.

 

[Spi D]

Provided your prop is undamaged all the above is true.

The easiest way to improve mpg is remove dead weight from the boat and be careful with the throttle.

 

[Photographer]

Thanks so much for all the info!!!!

 

[Photographer]

The easiest way to improve mpg is remove dead weight from the boat and be careful with the throttle.

Do you refer to my wife.... LOL (I hope she doesn't read this! )