Classic 18 Prop Question

[John Grinder]

I recently bought a 2005 Classic 18. Mercruiser 5.7L 300hp, Alpha One stern drive. At 5000 rpm I am going 60mph. At full throttle I am approaching 5400 and 65mph. I do not want to run over the red line of 5200, but I would like to be able to operate at full throttle with maximum speed.
the prop is a 3 blade stainless. The only markings on the prop are the numbers 9170 and 21. There are no manufacturer markings I can locate. I don't want to invest in a new prop of higher pitch without some confidence with what I am doing. Any advice you could offer would be appreciated.

[Lenny]

Try a 23" Merc cleaver. ( three blade ) I do like it on my 18. Expect to see about a 5000-5100 WOT with that and a light boat ( load ) Everyone here seems to have a favorite of their own liking due to preferred ride characteristics, etc.

[Greg Guimond]

I recently bought a 2005 Classic 18. Mercruiser 5.7L 300hp, Alpha One stern drive. At 5000 rpm I am going 60mph. At full throttle I am approaching 5400 and 65mph. I do not want to run over the red line of 5200, but I would like to be able to operate at full throttle with maximum speed.
the prop is a 3 blade stainless. The only markings on the prop are the numbers 9170 and 21. There are no manufacturer markings I can locate. I don't want to invest in a new prop of higher pitch without some confidence with what I am doing. Any advice you could offer would be appreciated.


For a deep drive like yours I would borrow and try a Mercury Rev4. It's a through hub 4 blade which you can get with PVS vents which I would suggest as an option.

[Pat McPherson]

For a deep drive like yours I would borrow and try a Mercury Rev4. It's a through hub 4 blade which you can get with PVS vents which I would suggest as an option.

I run a 25p Rev 4. Vary stable, 4mph faster mid range than a 3 blade and only 1 mph slower at wot.
I'd suggest trying a 23p Turbo 1 3 blade and 23p Merc Rev 4 4 blade.

[John Grinder]

I recently bought a 2005 Classic 18. Mercruiser 5.7L 300hp, Alpha One stern drive. At 5000 rpm I am going 60mph. At full throttle I am approaching 5400 and 65mph. I do not want to run over the red line of 5200, but I would like to be able to operate at full throttle with maximum speed.
the prop is a 3 blade stainless. The only markings on the prop are the numbers 9170 and 21. There are no manufacturer markings I can locate. I don't want to invest in a new prop of higher pitch without some confidence with what I am doing. Any advice you could offer would be appreciated.

Lenny, is this the Merc Mirage line of props?

[jl1962]

I have one season on my new to me 2004 18 350 MAG/MPI Alpha.

I haven't experimented w/ props at all, but my boat has a 23" Mirage Plus which seems like a great all rounder.

Good for low 60s (63-ish on GPS, speedo read higher) at 5000 rpms with no bad habits.