Spoiledrotten
Well-Known Member
My boat is a few weeks old now. I've got 30 hours on it and want to purchase another prop for a main, and use the current 13.5"/15p for the spare. I'd like to go with a 4 blade prop. I currently get around 24 MPH at about 5200 RPM. I think I can do better than this but don't know which way to go with the new prop. The specs below show an RPM range of 5000 - 6000. At 5200, I think some power is being wasted.
What would you go with to get the max performance out of my F90?
My boat is the Bennington SLX20.
![](http://i580.photobucket.com/albums/ss250/totallyrotten58/927077EC-18D9-4D0C-B8C3-D4742FA56CA7.jpg)
My motor specs.
F90 Specifications
Engine Type In-Line Four Cylinder
Displacement 97 ci (1596 cc)
Bore x Stroke 79 x 81.4mm (3.11 x 3.20in)
Prop Shaft Horsepower 90hp @ 5500rpm
Compression Ratio 9.6:1
Fuel Induction EFI/SOHC/4 Valves Per Cylinder
Exhaust Through Propeller
Intake Single Throttle Valve
Ignition TCI Micro Computer
Spark Plug LFR5A-11-00-000
Alternator Output 25AMP
Starting System Electric w/PTT
Lubrication Wet Sump
Engine Oil Capacity 3.7L/3.5L w/without filter
Full Throttle RPM Range 5000 ~ 6000 rpm
Cooling Water/Thermostatic Control
Recommended Engine Oil Yamalube® 4M (See owner's manual)
Recommended Fuel Regular Unleaded (Minimum Pump Octane 87)
Recommended Fuel Filtration Yamaha Mini 10-Micron Fuel/Water Separating Filter (external)
Ethanol Blend Limit 10% Maximum
Gear Ratio (25:11) 2.27:1
Gear Shift F-N-R
Shaft Length L = 20" X = 25"
Degree of Tilt 70°
Degree of Trim -4° through +16°
C.A.R.B. Rating 3-Star
Dry Weight 25" shaft / 169 kg (372 lbs) ; 20" shaft / 166 kg (366 lbs)
Steering Angle (maximum) 35° from center, either direction
Warranty 3 Year Limited Pleasure Boat - 1 Year Limited Commercial
What would you go with to get the max performance out of my F90?
My boat is the Bennington SLX20.
![](http://i580.photobucket.com/albums/ss250/totallyrotten58/927077EC-18D9-4D0C-B8C3-D4742FA56CA7.jpg)
My motor specs.
F90 Specifications
Engine Type In-Line Four Cylinder
Displacement 97 ci (1596 cc)
Bore x Stroke 79 x 81.4mm (3.11 x 3.20in)
Prop Shaft Horsepower 90hp @ 5500rpm
Compression Ratio 9.6:1
Fuel Induction EFI/SOHC/4 Valves Per Cylinder
Exhaust Through Propeller
Intake Single Throttle Valve
Ignition TCI Micro Computer
Spark Plug LFR5A-11-00-000
Alternator Output 25AMP
Starting System Electric w/PTT
Lubrication Wet Sump
Engine Oil Capacity 3.7L/3.5L w/without filter
Full Throttle RPM Range 5000 ~ 6000 rpm
Cooling Water/Thermostatic Control
Recommended Engine Oil Yamalube® 4M (See owner's manual)
Recommended Fuel Regular Unleaded (Minimum Pump Octane 87)
Recommended Fuel Filtration Yamaha Mini 10-Micron Fuel/Water Separating Filter (external)
Ethanol Blend Limit 10% Maximum
Gear Ratio (25:11) 2.27:1
Gear Shift F-N-R
Shaft Length L = 20" X = 25"
Degree of Tilt 70°
Degree of Trim -4° through +16°
C.A.R.B. Rating 3-Star
Dry Weight 25" shaft / 169 kg (372 lbs) ; 20" shaft / 166 kg (366 lbs)
Steering Angle (maximum) 35° from center, either direction
Warranty 3 Year Limited Pleasure Boat - 1 Year Limited Commercial