Why would I lie?

[goldnrod24]

I played with props yesterday. I know we have a prop/speed section, but this is more.


13.5 x 13 pitch = 38 mph @ 6000 WOT (Merc recommends 5800)


15 x 15 pitch = 43 mph @ 5600 WOT


Both props provide quick planing and lots of mid-range acceleration.


Dealer (who had pitched to me how thorough they are with lake testing for optimum prop selection) said he had NEVER heard of someone dropping RPMs at WOT and gaining speed. He was polite, but I could tell he thought I was BS-ing him. I'm NOT dealer bashing, just perplexed.


Since my testing was GPS verified and performed on the exact same water with identical fuel load/driver and weather conditions, the ONLY variable was the prop.


So again..... What to I stand to gain by lying?

 

[lakeliving]

Some just know it all... And the dealer must be one of them. So keeping the 15 pitch? 

 

[goldnrod24]

So keeping the 15 pitch? 

Absolutely! It's a different animal with the 15. Smoother at all RPMs. I know that sounds weird. Maybe it is just better balanced that the 13 was. I'm sure there is a range of manufacturing tolerances.


Moral of the story? Trust but verify.

 

[kaydano]

You are not lying.  


And your dealer's an idiot. 


Look at it from the other direction, going from the 15 down to the 13. Looking at it that way, you went to a prop that increased rpms and went down in speed.  Say you try an 11 next. Your rpms would continue to go up, and your speed would drop.  Take it all the way to an imaginary zero pitched prop:  infinite rpms, zero speed. 


Your data makes perfect sense  to me. 

 

[Bamaman]

I assume you've got an Enertia 15 pitch prop? 


At those speeds, you've obviously got a really good prop and setup.  Most boats are slightly slower with the 150 FourStroke.

 

[goldnrod24]

I assume you've got an Enertia 15 pitch prop? 


At those speeds, you've obviously got a really good prop and setup.  Most boats are slightly slower with the 150 FourStroke.

Correct. I should have mentioned that detail. Thanks for the clarification.

 

[Bill N]

I'm always interested to see these real world numbers.


How do you intend to use the boat? Reason I ask is if you put 3 more adults on board or an inflatable in tow and your results would be interesting as well.(I suspect the 13 would shine in that compare)

 

[goldnrod24]

I'm always interested to see these real world numbers.


How do you intend to use the boat? Reason I ask is if you put 3 more adults on board or an inflatable in tow and your results would be interesting as well.(I suspect the 13 would shine in that compare)

You may be right, Bill. I will report back when that situation arises.


My experience is that passengers don't care.

 

[Bill N]

Cocktail cruise speed...6 mph


Either prop will work just fine!