Prop Pitch

[Rusty Boater]

1999 Bayliner Capri 17.5
Merc 3.0
Alpha One

Ok so it warmed up enough to take the boat out. I replaced the tach and ran it out on sunday. I bought the boat last year and the prop is pretty chewed up and needs to be replaced. I cannot find a number on the prop anywhere. Right now at WOT it runs 4800 RPMs at about 44mph. Is that about right? Someone told me it should be a 14 x 19P. Also when I order a prop from here (Michagan Wheel) is there a prop hub kit also or does that come with the prop? Thanks for all the help!

 

[Silvertip]

Re: Prop Pitch

Did you take the prop nut and washer off and look at the hub for a part number or diameter and pitch? They are generally stamped on the hub or cast/stamped into the hub. 4800 is about right. Whether or not you need a hub kit depends on the prop you buy. If has an exchangeable hub system, the hub kit will be listed along with the prop. If the prop has a rubber cushioned hub thats an integral hub design and there is no separate hub.

 

[Rusty Boater]

Re: Prop Pitch

I removed the prop and found this part # 48-832832-C1-21

I tried to google it and came up with really nothing. Anybody know what size this is? I thought this was a 19P but i am guessing that 21 means 21P. What to do? I am at 4800-4900 right now. If i go to a 19 what happens?

 

[steelespike]

Re: Prop Pitch

I removed the prop and found this part # 48-832832-C1-21

I tried to google it and came up with really nothing. Anybody know what size this is? I thought this was a 19P but i am guessing that 21 means 21P. What to do? I am at 4800-4900 right now. If i go to a 19 what happens?

Not an expert but I would guess a 21 as well.I would get the prop repaired
cheaper than new, test her out again. Not sure what your max rpm should be
but my guess ia about 4,600.My guess is your rpm will be closer to what you need.Once we see that with the repaired prop we can decide where your at.
It would appear a 19 would put you way high of your recommended rpm range.Each inch yeilds about 200 rpm change. Lower pitch higher rpm higher pitch lower rpm.Difficult to make a change without readings from a sound prop.

 

[Silvertip]

Re: Prop Pitch

That is a Mercury prop and it is a 14-1/4 x 21P. If you dropped to a 19P (assuming the same prop design) the engine rpm would go up by about 300-400 RPM which puts you well over the recommended WOT rpm range. Stay with the 21P unless you do a lot of water sports (skiing, tubing, etc.) In that case the 19P gives you better hole shot and towing ability but you need to watch the tach so you don't over rev. Just remember, a 21P prop from one manufacturer may not and generally will not have the same performance characteristics as a 21P from another manufacturer. The are close, but not identical. Also understand that just because the engine runs faster, the boat doesn't go faster. Raising the rpms means the engine needs to run faster to maintain the same speed you had with the 21P.

 

[Rusty Boater]

Re: Prop Pitch

Thanks for the input; i have ordered a 21p from here last night. We do ski, tube, and wakeboard a good bit. but the 21P has been OK and i think a prop just in great condition will improve performance while water sporting.