Time for a new prop? Any reason to?

[Ki Ki]

I have a 14' Grumman Fishing boat V Hull. 30 HP JOHNSON 1995 motor.
I get about 20 mph top speed with this prop. As far as I know, it's the original prop and has some dings and chips on it. Definitely looks far from new.

I don't tube or anything, but to like to open it up here and there. Is there going to be noticeable benefit to replacing the prop?

 

[gm280]

The first thing you need to do is see what the WOT RPMs are before buying a new prop. If you're not in the WOT RPM range, then you need to buy a prop that will allow you to rive to that WOT RPMs range. If you don't have a tach at the helm, you can buy a "Tiny Tach" and use it to see what your WOT RPMs are presently. Because if you are not at the proper WOT RPMs now, your engine is not running in the proper range. And if you are over riving the engine, you also need to know that to buy the proper replacement prop... JMHO!

 

[steelespike]

If that's just a bare bones utility 20 is very slow. Well setup should net close to 30.

 

[ttankmoran]

Agreed, 20 is slow, get a tach to see where you're at for rpm's when you're wide open. close to 30 should be attainable with that engine, had a 18ft pontoon with the same year 28 SPL, same powerhead (crappier lower unit) and could touch about 17 mph.

 

[sasto]

What is the RPM of the motor at WOT with current prop? Hard to tell without this vital info.

 

[fhhuber]

If that's the OEM prop that came with the engine the size will be appropriate for the engine. Potentially more speed by trading pitch for diameter... For a heavy load you go down in pitch and up in diameter and can actually gain speed.
But i don't think that is what you are asking at all...

Depending on how dinged up the prop is.

It can be imposing unbalanced load on the prop shaft and that can damage the lower end.

Might not need a new porp... they can straighten and clean up the old one and re-balance it.
After they get really bad though its time to replace.