prop size question

[roffey]

My prop is bent, must have hit the mud..... Any who I need a new prop. My current prop is the one that I got with the boat. Its a 23 inch and WOT I hit 5000 RPM. MY motor is a 4.3 and the recommended RPM is 4800, so I think I am right in the manufacturer specifications. My question is if I go with a stainless prop should I go to a 24 inch or stay with the 23. IMHO, I think I am right on the line for RPM and a steel prop is lighter and might over rev the motor. I do not go WOT normally but every now and then ......

 

[Alumarine]

Might be better to ask in the prop section but I always thought that if you go from aluminum to stainless all thing being equal you should go down a size.
Therefore 21.
I'm not a prop expert at all.

 

[Sea Rider]

SS is way heavier than alum props, if with a 23 prop achieves 5K revs, going down one size to 22 should achieve same rpm, right or wrong ? If right will need to repitch current one as probably there isn't a 22 pitch market available.

Happy Boating

 

[alldodge]

Would need some more info to determine if your slip numbers are correct.
Need drive ratio and a gps reading for mph. Will also need to know if your Tach is accurate, most are not

Otherwise stick with 23, aluminum or stainless and watch you rpm's.

 

[roffey]

depending on wind I go from 52.9 to 54.2, on the gps. Tach is 4900 to 5000 depending on how far up the drive is. I trim it until I start to lose MPH. not sure on the drive. I will look around and see what numbers I can come up with.

But you guys think I should go down in pitch, or as AllDodge said just watch the rpm. It sure would be nice if you could test drive a prop first.

 

[alldodge]

Using the 4.3 normally has a 1.81 drive and if everything else is correct you have 11 percent slip (using 53 mph), which is not bad. Being a small boat it should be below 10 percent. Many places will let you test a prop, but there are many more that have you lay down a deposit for your next prop

 

[roffey]

I would happily put down some cash to test a prop as I am in need of new one. Thanks for the info...

 

[superbenk]

PropMD has a pitch exchange program & are great at working with you. I'd recommend giving them a call & tell them your numbers. They'll give good recommendations & work with you until it's right. I've been really happy with them both for repairs & recently a prop purchase.

 

[roffey]

ill give them a call