Is this the right prop for my boat?

[stack08]

I got a 1989 force 125 outboard and a 17' invaders bowrider

I got a 13x19 alluminun prop is this ok for my boat or what would be my options?

At wot I go about 44mph....

This is what came with the boat.
What the difference in alluminum prop to stainless steel prop?

Thanks...

 

[mthieme]

Re: Is this the right prop for my boat?

You really need to measure the rpm at WOT to get an accurate answer. However, you're in the neighborhood.

Do a search on "SS" & "Aluminum". You'll have much reading to do.

 

[Frank Acampora]

Re: Is this the right prop for my boat?

Do you have a tachometer? If you do and are reading between 4500 and 5500 RPM at WOT, then the prop is correct--however, it is always better to run nearer the top of the RPM range SO:

A stainless prop will gain about 400 RPM and about 2-3 MPH (maybe more depending upon hull and engine) over the same sized aluminum prop from the same manufacturer.

If your engine is now running 5500 with the aluminum prop, then a good guess would be to use a 13 X 21 stainless prop. That should keep it close yet still increase speed. Note that I said guess--nothing is etched in stone.

And without a tachometer, you really can not do anything but guess. It's like taking a trip: If you don't know where you are, how can you figure how to get where you are going.

 

[coastalcruiser]

Re: Is this the right prop for my boat?

I lost a aluminum blade on my singleprop Mercruiser a few years ago because of a small piece of wood. Always carry a spare prop!

Getting ready to install a duoprop and came across this in the Volvo service manual about SS props.

Quote:
CAUTION D-series aluminum propeller sets used on
Duoprop applications are not recommended for use on boat
and engine combinations capable of speeds in excess of 40
MPH. F-series stainless steel propeller sets should be used