3300scr new props and intakes

[queenendorf]

Good Day all

I have a 2001 3300scr with 5.7l mercruiser bravo 2 drives.
I have decided to change my 2 barrel carbs over to 4 barrel. This involves new intakes as well as the carbs.
Currently I have 19 pitch 19 inch ss props.
With the increase in HP i will get from the 4 barrel carbs (about 15 per side), it was suggested to me that I could to go up a pitch size on the props.
Going from 19 to 21 for example should increase my top end and allow me to have a higher "sweet spot" .
with lower rpms.
With the secondary barrels closed I should save fuel while cruising.
The question I would like to pose is this.
Is there any advantage to going to 4 blade 20 pitch SS?
Look forward to hearing your thoughts

[shrew]

The drive is geared the same so i'm not sure that an increase in HP would make a difference. Once upgraded, use the MAX RPM range of the motor and the actual MAX RPM your getting as a guide to properly sizing the wheels. The 5.7L (carb) should have a Max rpm range of 4400-4800 RPM's. At WOT with proper drive and tab trim, in realtively calm seas, what is your actual MAX RPM?

If Actual Max RPM is under 4400, you are overpropped.
IF Actual Max RPM is over 4800 you are under propped.

If it is anywhere between 4400-4800 you are running OK. Many will say you should be as close to 4800 without going over.

I've never seen prop sizing that uses HP alone. I've never seen one that uses Speed at all. Just a couple of thoughts.

IMHO you're going to increase fuel consumption with no appreciable increase in performance. I went from 300HP to 375 HP and saw very little change in overall performance with the same prop.