Does Size Matter?

Just had my engine serviced (Mercury Outboard 50hp 2 stroke) The chap suggested I change the propeller as it was kinda beat up. I am new to boating so took his advice. I was given a spare propeller when i bought the boat, so we replaced it with that. I just noticed that the replacement prop was just a fraction smaller than the beat up one we took off. Will I notice a massive difference in performance with a smaller propeller? Advantages disadvantages?

Re: Does Size Matter?

No way of knowing the answer to that one without running the boat with a tachometer, normal load, and speedometer (GPS is better).

Re: Does Size Matter?

Sure thing... but the rule doesn't go that a smaller propeller would provide less propulsion therefore less top speed and/or acceleration? Or is my thinking a bit to obvious there?

Re: Does Size Matter?

Running with a prop that is not right for your boat can cause serious expensive damage. You'll need to provide the information requested above for assistance. Do yourself a favor and don't just assume it will be okay.

Re: Does Size Matter?

Putting a prop on a boat/engine package is like putting on new shoes, Griz. If it doesn't fit the package you will have trouble.

Go to the Prop Forum and get an education on finding the right prop.

Re: Does Size Matter?

sometimes even correct props for the application, but from 2 different manufacturers might have slightly different total diameter of the blades (by like a 1/4" to 1/2" or so). If you check the part number on it, you might be able to find out if it was intended to be used on your motor. Or maybe it is intended for a 40 hp or something else. Even if it is appropriate for your motor, the pitch may be very different than the other one. A difference in pitch will make more of a difference than a small difference in blade diameter. Props that are made to be used on your motor will come in a whole range of pitches to allow the motor to be used on a range of different boats. (light vs heavy) Sometimes people have 2 props... a "speed" prop with more pitch, and a "ski" prop that has less pitch, but more pulling power... so just because it is a spare, don't assume it's the same pitch as the other one.

Re: Does Size Matter?

Its beautiful old wooden camping boat. However the dude i bought it from did mention water skiing, in conjunction with this propeller. I would never water ski from the damn thing. Thanks for all the advice so far. I am off to the stockist tomorrow to pic up a replica of my old beat up prop. The replies here have scared the bejesus out of me... so better to stump up the cash for a new prop, than stump it for a new motor.

Re: Does Size Matter?

http://forums.iboats.com/showthread.php?t=234025