Prop size question

[JJB]

I Have a Johnson 2000 175 with a 18" pitch ss 4 blade prop . My wot is at 5200 rpms and should be 5500 rpms . Would going to a 3 blade 17 " aluminum prop get me to my 5500 wot max rpms ?

 

[steelespike]

Re: Prop size question

Not an expert but:: you may want to fine tune your setup then make a decession on a prop.
Would be good to know what boat and max speed.Usually a 4 blade will lower max rpm some going to aluminum could give you a little and 1 inch pitch change a couple of hundred.So yes it would seem it would get you there.
The aluminum might give a little less performance.I think to keep it simple
I'd go to a 16 or 17 3 blade stainless.You might gain a little hole shot and top end (unusual) and get to your rpm.

 

[MikDee]

Re: Prop size question

I Have a Johnson 2000 175 with a 18" pitch ss 4 blade prop . My wot is at 5200 rpms and should be 5500 rpms . Would going to a 3 blade 17 " aluminum prop get me to my 5500 wot max rpms ?

Just Dropping to a 3 blade prop, will bring your rpm up, a coupla hundred rpm Dropping to an aluminum prop would also bring your rpm up, a coupla hundred rpm!
I'd say you could probably go to a 19" pitch aluminum prop, and still get the rpm you want, you may over rev with a 17" prop, IMO

 

[JJB]

Re: Prop size question

The boat is a 20' bayliner with 2000 175 Johnson on it . I was doing about 45 mph at about 5100 to 5200 rpm with the ss 4 blade . I like the four blade the way it keeps you on plane at lower rpms in the rough seas . I dont care about top speeds just want to keep in proper rpm range . Are there any different factors you need to take into consideration when using a 4 blade ss as compared to a 3 blade ss or aluminum ? Like if I was using a 3 blade 17" pitch ss prop and was in the right rpm range , would I need a 16" pitch ss 4 blade prop for same results ? Thanks for the input !

 

[Silvertip]

Re: Prop size question

Before buying another prop, work with setup (as in engine mouting height). Going up one hole may get you the couple hundred RPM you need. When doing that however, you are advised to install a water pressure gauge so you don't go so high as to lose water pressure. Its a good investment anyway.

 

[JJB]

Re: Prop size question

I have work with the height and have it as hight as it will go and do have a water pressure gauge on the boat . Still 300 rpms under at wot . with the 18" 4 blade ss prop