What is the factory prop for a 2005 Sylvan V-160 with a 2005 Johnson 70hp fourstroke
It all depends on what your using your boat for. Fishing, sport or pleasure or all of above. What kind of load you have. How many people, how much fuel or how big is your cooler. The most important thing is if your prop is running in the (W.O.T.) wide open throttle numbers for your engine. Your numbers are; 5200 - 5800 rpm's. The factory or for the most part, the dealer will put a conservative prop on. A aluminum three (3) blade -13.25 x 17 or 13 x 19 cupped. For a heavier load (lift,thrust, hole shot) you can run a 13.75 x 15 or for a light load (high speed) you could run a 12.75 x 21. More than likely a 13 x 19 cupped is what will run the best being that Sylvan is a fast planing hull. A four (4) blade propeller will give you a better hole shot and better mid - range control but is rarely to never put on at the factory. That only happens at the dealer and it's usually from profit margin on stainless steel or personal preference. The maximum horse power output on your motor will be at 5400-5600 rpm's.
******** (W.O.T.) Wide Open Throttle Numbers ********
The propeller pitch and the gear ratio of the engine sets the burn on the motor. It's got nothing to do with anything except proper consumption of fuel on the engine. Some people will say" Well I never go that fast or I only cruise at 4000" That dose not matter, it's set for...... PROPER CONSUMPTION OF FUEL ONLY. If you are not running in the W.O.T. numbers you are running rich or lean, either way you will blow up your engine.
To find your W.O.T. numbers: A new or reconditioned propeller only...no damage.
(1)Run your boat as fast as it will go, throttle all the way home. Conditions to your favor (wind to your back, water like glass, little to no chop).
(2)Trim the engine down to ninety (90) degrees off the stern, prop horizontal to the hull. The stern will lift and the bow will plow and you will lose speed.
(3)Look at the tachometer only, not the speedometer, just the tachometer. That is your (W.O.T.) wide open throttle number. Trimmed up will throw your numbers out by about three (3) hundred so as long as you are in your W.O.T. numbers pushing 5800 plus is ok as long as you don't hit your rev limiter, which is usually 6050 or a little higher.
Thanks for you question. propguy513
