evinrude 9.9 hp prop question

[lil mikey]

Good Morning,,I have a 14ft Princecraft with a 9.9 on her ,and was wondering prop size I can go up to,,,,it currently has a10x7pitch prop,,i just had it out and would like to get a lil more mph out of her,,,How bigger prop does anyone think I can go with? Its not a tiller and has steering control,,,,i know the motor is a lil small for it,,,Thanks in advance...Mike

 

[steelespike]

A 7" is a size for something like a kicker on a large boat.
You should really have a tach for sizing a prop.
We really need your rpm and gps speed.
Also need to know your typical loads.
Is this a bare utility with a steering console?
What year and brand motor?

 

[lil mikey]

steelespike! its a 1997 Evinrude,,it does have rod lockers and a wood platform so she isn't bare boat,, doesn't have a tach in but I'm looking to put one in. When I went to prop section is calls for a 10 pitch,,maybe start there ?? what would be the WOT RPM should be? Thanks for taking the time to reply,,Mike

 

[oldboat1]

I agree with Steelespike. The prop on my '80s 9.9 was a 9 1/2 X 10, which I think was standard. If you ran that prop, it would probably make a big difference.

I went to a four-blade 10 X 5 because I use it as an auxiliary on a big hull -- and a 10 X 7 would probably have been fine for my application too.

(I wonder if maybe you have a longshaft motor with a thrust prop, maybe originally for use as an auxiliary on a sailboat. My Yachtwin has a 25" shaft, or thereabouts -- suggesting maybe your motor might have a long shaft (20 or 25") along with that lower pitched prop. If so, you might be getting extra drag there. Just a thought -- not sure what transom height you have on your Princecraft.)

 

[lil mikey]

Oldboat1 yes its a long shaft,,,the Princecraft was bought new in 1997 with the motor that's on it,,,,I'm gunna try the 9 1/2 x 10 pitch,,,,Thanks again to all who replied,,Mike

 

[steelespike]

Rpm rating is 5000 to 6000.Normally you would prop toward the 6000.
While a 10" may deliver more speed it may seem sluggish in hole shot and added weight compared to the 7".

 

[Sea Rider]

Bump that 9.9 into a 15 HP, both are 250 CC powerheads. Will need to change reed valve assy, gaskets and a new 15 HP carb, install an induction tach, go for a wot spin while lightly loaded and play with prop pitches all you like to achieve near max wot rpm for that OB. If boat has a small transom height will ned to install a engine mount, jack plate to rise OB accordingly.

Happy Boating