Would a different prop help?

[fokker416]

Hello all, I own a Hunter 23.5 with a Mercury 9.9 long shaft. I'm pretty sure the hull is rated for 6kts. The motor is about 2 years old, well maintained with moderate use. At about 3/4 throttle I will get about 6-7kts and when I go up to full throttle my speed really doesn't change much so I'm basically burning extra fuel for no good reason. I have the stock propeller. I am wondering if I change the propeller will that give me any extra speed with a full throttle. Or would a motor fin (I can't remember what their proper name is) be a better solution? Thanks for the help in advance.

 

[Fly_H23]

Hull speed is the theoretical limit without getting your boat up on plane like power boats do. A different prop may add a tad more top speed at the cost of low speed thrust to get you moving or stopped at a dock.

Any speed increase will eat much more fuel also. You might think about how smooth your bottom paint is? A rough or dirty bottom can cost a knot or two of top speed.

 

[Benny17441]

You would only be wasting fuel. The theorical hull speed for your boat is 6.2 knots and conceivably with newer hull shapes it could be in the vecinity of 6.5 knots. You can go faster but any small increase in speed will require disproportionate amount of horse power and fuel. If it were me I would get a prop that would allow the boat to reach 6.5 knots at 90% of rated RPM. Its easier to gain acceleration than to get increased top speed.