F2.5 vs F4 propeller

[almetelo]

Hi!

Have a F4A or F4M used a couple of times a year just for *****ing fishing on a KL 16 boat.
Seems I'm over proped, I have the lowest prop listed for this model 7-1/4"X6-1/2" and I dont even reach to 3000rpm (lightly below)
Did a little timing advance (1 dent) but didnīt noticed a diference also tryed rejeting with no results at all.
Now I'm heading to try the F2.5 prop (if will do) because those have lowest pitch available but I donīt know if prop shaft is the same size and same number of splines.

Anyone can answer this?

Thanks!

No, buy other motor is not an option for now even more for such little use. I just need 1 more kts

[rodbolt17]

don't know about knots but you NEED another 2000 RPM or so.
that poor tiny mite is seriously lugging and is begging to put a hole in a piston.
what pitch and diameter are you running now?

[almetelo]

Yes, more RPM's and at least 1 knot is what I need.

The prop I have is the 7-1/4"X6-1/2 the lowest pitch and diameter listed on manual for this model.
I need a lowest Pitch prop and a maybe a little more diameter.
The F2.5 have lowest pitch available just donīt know if will do...

[rodbolt17]

I would have to look at the prop selector chart to see if the F2.5 prop fits.
however any propshop can alter your current prop.

I have a friend with an F50 mounted on a 21 chawk that I have to buy the smallest F50 prop and have it cut to 11 1/4 x8.

yes it is rather underpowered.

[almetelo]

The F2.5 have this 2 props that may could improve RPM and either speed. (if feat on the F4 prop shaft)

7-1/4"X5" or
7-1/2"X5 1/2"

[almetelo]

On the F4 props listed after the number on prop have these 2 letter (BA) EX: 7-1/4"X6-1/2BA and the F2.5 the letters (BS)

Must have a meaning for sure but dont know if is relevant

[almetelo]

Never heard about cut the props over here...
Who only possibly can to that is companies that repair props, we have 2 around and will hear what they say.
But would like to know if the F2.5 prop will feat on F4 prop shaft anyway in case they donīt do that here, when you have the time and patience, if you do... (its not a hurry)

Thanks!

[almetelo]

Hi!

My local yamaha dealer doesnīt have any F2.5 on stock or for repair at the moment, not even a spare prop so I gone to next city with Yamaha dealer (about 10Km's) and they have one F2.5 on stock so I could check if the F2.5 prop will do on the F4 and guess what...Yes, will do! I checked my F4 prop on the F2.5 prop shaft and the "size" is the same.
But isnīt all good news... the price of the F2.5 prop here is incredible HIGH!!! 96€ (+/- $130) This is almost the price of a new original prop for my 30hp

But the most important is that will do and I'll be looking for the prop on ebay.

Thanks anyway!