Prop size; 11' tunnel hull inflatable

[Jeff Salinas]

Hello everyone,

This is my first post. I would like to ask recommendations on which prop size I should use on my 11' tunnel hull inflatable AMI Sportcat with a 2005 Mercury 15HP outboard. Currently with my setup and the stock prop on my 15hp; I think I am over revving the motor at full throttle as the rev limiter starts to kick in only when I open it all the way up.
I think the current stock prop is a 8" or 9" pitch. I am thinking going over to a 13" pitch. Can someone please share with me their knowledge and experience in pairing prop size with boat and motor. This is my first boat and I'm trying to tune it in to optimal performance in top end speed with out over revving it.

Thank you,

Jeff

 

[steelespike]

Re: Prop size; 11' tunnel hull inflatable

Really need max rpm and speed and actual prop size.A "tiny tach" will get your rpm, check the net reasonable easy install work on any similar engine without regard for poles.Difficult to know where your at without these specs.
It could be as simple as a change to stainless (if available)
9" to 13" would lower your rpm by about 800.Seems extreme to me.
Does the prop seem to have a good bite?

 

[Jeff Salinas]

Re: Prop size; 11' tunnel hull inflatable

Hi Steelespike,

thank you for all the response. I guess my next step would be to order the tiny tach. and go from there. but, do you think that the root of my problems would be the Doel-fin that I have installed. I have since removed it but have not had a chance to run it yet till this weekend. I'll soon find out. does it sound possible of a hydro foil over reving a motor on WOT?

thanks,

Jeff

 

[steelespike]

Re: Prop size; 11' tunnel hull inflatable

Probably not the foil but they have been known to cause all kinds of problems when not right.

 

[Jeff Salinas]

Re: Prop size; 11' tunnel hull inflatable

Steelespike,

I have another question please regarding prop choice and diameter. I know the standard prop that came with my Merc 15HP is a 9x9. I'm just wondering why is it when I searched for different props for this exact motor the iboats online store all came up with different diameter props;10" and on. I measured the clearance of tip of my stock prop to the bottom of the cavitation plate and I only get 1/2" clearance. Before deciding on the tiny tac I planned on getting the Solas Amita prop; 10 1/2" x 11". According to my measurement this diameter would not fit my motor but this is what comes up when searching for different props for my motor. do you think you can please enlighten me on the different diameter props that are supposedly for my 2003 Mercury 4 stroke 15HP.

Thanks again,

Jeff

 

[steelespike]

Re: Prop size; 11' tunnel hull inflatable

Steelespike,

I have another question please regarding prop choice and diameter. I know the standard prop that came with my Merc 15HP is a 9x9. I'm just wondering why is it when I searched for different props for this exact motor the iboats online store all came up with different diameter props;10" and on. I measured the clearance of tip of my stock prop to the bottom of the cavitation plate and I only get 1/2" clearance. Before deciding on the tiny tac I planned on getting the Solas Amita prop; 10 1/2" x 11". According to my measurement this diameter would not fit my motor but this is what comes up when searching for different props for my motor. do you think you can please enlighten me on the different diameter props that are supposedly for my 2003 Mercury 4 stroke 15HP.

Thanks again,

Jeff

I'm no expert on the prop store but the only 10" diameter props I found were for big foot motors.Yours shouldn't be a big foot.All the other 15 hp motors
came up with 9 1/4" diameter.check the spline. Sku number 1111-093-11
91/4" X 11".

 

[Jeff Salinas]

Re: Prop size; 11' tunnel hull inflatable

Hi Steelespike,

those 10" plus diameter props state they are for the bigfoot and the 15hp fourstroke;

1999 & Newer 15 HP Mercury or Mariner 15 HP (Bigfoot, 4-Stroke) (Thru Hub Exhaust & 10 Tooth Spline)

Oh well, no worries. I know for certain the correct prop to get would be by blackmax. It's a little bit more pricier than the ones we have here, but it will fit for sure.

thanks for all your help Steelespike.

Jeff

 

[steelespike]

Re: Prop size; 11' tunnel hull inflatable

Hi Steelespike,

those 10" plus diameter props state they are for the bigfoot and the 15hp fourstroke;

1999 & Newer 15 HP Mercury or Mariner 15 HP (Bigfoot, 4-Stroke) (Thru Hub Exhaust & 10 Tooth Spline)

Oh well, no worries. I know for certain the correct prop to get would be by blackmax. It's a little bit more pricier than the ones we have here, but it will fit for sure.

thanks for all your help Steelespike.

Jeff

I read that as merc and mariner bigfoot and big foot 4 stroke.
it is a 10 spline as well.
Maybe I missed something but it appears all else are 8 spline.
fitting 2 stroke and 4 stroke.Is yours 10 spline?

 

[charles98888]

Re: Prop size; 11' tunnel hull inflatable

i HAVE THE SIMILAR QUESTION WITH A SIMILAR BOAT AND MOTOR..i HAVE THE HONDA BF15HP SPINNING STOCK AND HAVE DISCOVERED A FOUR BLADE ON SOLAS SITE WITH 7" DIA.. SKU-3113-100-07 SINCE THE RECOMENDED SETUP IS AT OR SLIGHLY BELOW THE HIJACKERS CENTERLINE.. WOULD NOT THIS SEEM TO BE ALLMOST A SURFACE PEIRCING PROP APPLICATION?..HAS ANYONE TRIED THIS? OR IS THIS PROP SIMPLY FOR HIGH TRUST APPLICATIONS?..MY GOAL IS MAX MPG OVER WATER WITH TWO ADULTS

 

[deejaycee_2000]

Re: Prop size; 11' tunnel hull inflatable

get a stainless 13p ...... set your motor flat on the transom, and run it on trim 2 .....