Max rpms with a 4 blade prop for yam F115

[mandopickr]

Since I didn't get any response from my previous question, I am going to rephrase my post to see if this is bettter:
I have a Key West 196 Bay Reef with a Yam 115 four stroke. It could use some stern lift, and I would also like to improve the mid-range performance, in the 3500-4500rpm range. From what I have read, it appears that a 4 blade prop may help with the stern lift, though it may affect my top end. I rarely run more than 4500 rpm, so top end is not an issue.

Currently using the Yam 16-K black ss prop, which is 13.5x16. Wot is 5800. I also would like to get the max rpms closer to 6000.

My thinking is that going to a al 4 blade prop would be a wash for rpm and speed, no improvement in top speed or wot rpms.

Then if I drop down to a 15 pitch it should improve the rpms by about 200(?), which would increase my rpms closer to 6000.

What would happen (theoritically) to the rpms if I also went to a 13". Amitas has a 13x15 prop that I am considering. (However I went to the Mercury prop calculator and got totally confused. It suggested a 17 or 19 pitch).

Any thoughts on the correct 4 blade prop.

 

[steelespike]

Re: Max rpms with a 4 blade prop for yam F115

Before a prop change check your setup.The antivent plate,just above the prop,
should be visable on plane.What is the speed at wot?
A material change makes the results less predictable and a design change becomes even less predictable.I would suggest a Solas amita in a 15". It should give you hole shot,stay on plane with less throttle.handle better on plane and at the dock.
Not really able to tell rpm results, likely lose some top end.

 

[mandopickr]

Re: Max rpms with a 4 blade prop for yam F115

wot is 5800 rpms and 37.5 mph

my main goal is stern lift. If I can get the boat on a better plane between3500 and 4500, I think the mph would improve as well.

Thanks for your comments

 

[Tail_Gunner]

Re: Max rpms with a 4 blade prop for yam F115

Currently using the Yam 16-K black ss prop, which is 13.5x16. Wot is 5800. I also would like to get the max rpms closer to 6000.
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Yamaha owns precison...dont know if the retail line is shared with the oem but it would make sense..Now if that is a precision prop its agressive...

16@5800
drop 200 for ss...16@6000...add 100 for the 4th blade....5900

I dont see a 13 any place here..15 or 16...do a 16 and run the motor higher..thats where a 4 blade shines....I am going to get a outboard combo some day..........