Just about there with the Monte Carlo

[dsolaro]

I am just about ready to launch my Monte Carlo (pictures to follow after it is washed and waxed this weekend) but I am in need of a prop size. I am running a PCM ZR6 at 375 HP. Does anyone have an idea where I can start with a prop size? I have a friend who owns a boat shop and will let me try several sizes before I buy, but I would like to start out pretty close. Any ideas?

[Trackhappy]

Hi Dave. Well done getting this far. Not quite enough info for us to help yet though, (bearing in mind that I am no expert).
What is the maximum prop diameter you can fit?
Any reduction in the transmission?
What is max engine RPM?

My 5.7L 325HP Small block has a recommended starting place of 12 x 14 or maybe 12 x 15 with no reduction and max RPM 5500. My guess for you would be 13 x 14 or 13 x 15 but there is also cupping to consider.

[DaveLott]

Ok, Dave - need to know - are you straight drive or do you have the down angle reduction transmission PCM mates with these engines.

I can tell you that you will need some meat for a prop. I have the PCM 343HP and had to go to a 13.5x16 four blade overcupped to .130 just to keep the engine within RPM tolerances. I originally had a 13x16 three blade. The engine would exceed rpm tolerances in a blink of any eye. I went over 7000 RPM a couple of times with that blade.

So I expect you will have to start with something like the 13.5x16 four blade. What is your drop on your strut?

dave

[DaveLott]

Ok, Dave - need to know - are you straight drive or do you have the down angle reduction transmission PCM mates with these engines.

I can tell you that you will need some meat for a prop. I have the PCM 343HP and had to go to a 13.5x16 four blade overcupped to .130 just to keep the engine within RPM tolerances. I originally had a 13x16 three blade. The engine would exceed rpm tolerances in a blink of any eye. I went over 7000 RPM a couple of times with that blade.

So I expect you will have to start with something like the 13.5x16 four blade. What is your drop on your strut?

dave

[dsolaro]

I am using the PCM 1.23:1 down angle transmission. The manual indicates that the max RPM is 5300 with 5200 being preferred. I used a 16 degree 7 1/2" drop strut which should give me plenty of room for a 14" prop if needed. I appreciate the help, and as soon as the weather clears up this weekend I will get some pictures to show her off.

[DaveLott]

You have the exact same setup I have. A 14" prop will be too big. The recommended clearance between the prop and keel is 2". I am closer than that right now. I thought of going to 14" but it would put me right at 1" of the hull and I worried about prop wash damage

[dsolaro]

Thanks Dave. I will keep that in mind when I start out with the sizing.