what size prop

[paleo10]

hello what size prop should i have on my 89 125 hp force engine it says operating range 4500 to 5500 how can i tell its pitch and size thank you
ps the boat is a 21ft pontoon normalaly carry 5 adults or less

 

[SpinnerBait_Nut]

Re: what size prop

Prop questions and topics

 

[Silvertip]

Re: what size prop

Have you read any of the posts on this forum? If you did you would know there is no way anyone can give you any information because you gave us absolutely nothing to go on. There is no "standard" prop for any engine/boat combination. Until you determine what you have now all anyone can do is guess. We need some speed and wide open throttle rpm to go on. WOT rpm is not what the manufacturer says it should be, it's what you are actually seeing on the tach. If its not in the range you indicated, then we can help but only if you tell us what prop you have now. Remove the nut and look on the hub.

 

[paleo10]

Re: what size prop

well first off siver tip dont be a jerk i dont know anything about it other than it is a used motor given to me for my boat i fiqured more expierinced boat people would know the standerd prop that would have came on the motor origanaly it is a 1989 125 hp force i dont know wot because the prop on it is probally to small and i dont wont to over rev engine with this prop so i wanted the corect prop for this engine which it origainaly came with i guess if you dont know the answer dont waste your time saying you dont

 

[Silvertip]

Re: what size prop

Thanks -- I've been called worse! Usually by people who can't stand to have someone suggest they actually "buy" a service manual. Back to your problem. Just to clarify -- engines 40 HP and over do not come with a "standard" prop. There is no such thing. Instead, a range of props with varying pitches are provided by the manufacturer and about a couple dozen other versions by aftermarket manufacturers. About the only thing standard is the diameter for a given HP range and even that will vary up to 3/4 inch. The manufacturers "recommended" rpm is not what's needed. It's what you actually observe at wide open throttle. If you are over reving, that's one scenario, if its unable to reach that rpm band, that's another. Below is a link to iBoats prop section: All the information you need is there. It even tells you that the 90 and 125 use the same diameter prop (13-1/2). The range of available pitches is 15 to 21. Based on the info you gave all I can say is pick one. On a pontoon -- probably a 15.

http://www.boat-props.com/propellers/s#sterndrive