Need advice

[farracatel]

Hi everybody,
I' m new in the forum and looking for some help.
I have a 5,5 m rib with a VFI hull (ventilated flow interruption, so i was told) with a mercury 4 stroke 60 hp big foot, 17 PT propeller.
The thing is, the motor never run above 4900 rpm max throttle, and the motor can go on 5500 rpm to 6000 rpm.
Why does the motor don´t go on top rpm? Should i change for a 14PT or 19PT propeller?
By the way the boat GPS top speed with one person in a lake is 28 Knots? I think it should go at least 30 Knots?

I would realy apreciate some help because me and my friends are sailing boat people, without experience in ribs, motors or propellers

THANK S

[9D280]

Firstly, welcome to ribnet.

Sounds like you could go down in pitch. the usual rule of thumb is 1" of pitch = 200 rpm. So, based on you aiming at 5500, I'd see if you could borrow a 14" and see what happens.

For what it's worth, my rib is a similar size & HP and I'm running a 14".


I'm now going to go & Google VFI.......

[farracatel]

Originally Posted by 9D280

Firstly, welcome to ribnet.

Sounds like you could go down in pitch. the usual rule of thumb is 1" of pitch = 200 rpm. So, based on you aiming at 5500, I'd see if you could borrow a 14" and see what happens.

For what it's worth, my rib is a similar size & HP and I'm running a 14".


I'm now going to go & Google VFI.......

Thank s for the tip i´ll try to borrow a 14".