Prop size
 

Hello Scarab Brothers & Sisters, I am new to this but have read alot of useful info. I am ready to install new 383s in my 79 300 what size props should I start with ? And trim tabs ? 9x30 or 12 x24 Drives are Bravo 1

how much horsepower do you think you have

they have 325 hp at the prop they are the mercs. 6.2 whjch are bored larger and longer stroke

I would say 21" if you had BBC's, I'd start with 19" 3 blades. What was your torque?

390 pounds

ya i agree i think 21s would work

My friends '89 Bravo Panther with 330's will spin a 23" mirage 4600. I assume you need more RPM's ~5500? with the small blocks to make your power. I would start with 19"

rpm at 5500 might be a little high my 350 mpi's
say they like the rpm around 4900 to 5000max on a stock motor but i guess that depends what you did with your motors

OK Thanks I read in the 383s specs. that it was sea trialed in a 86 sea ray pachanga, did not give size or weight w/ the 383, bravo one drive and a 24 pitch prop. the boat hit a top speed of 63 mph at 5000 rpm that was a 20% performance improvement over the orig. set up that was a 350 Magnum, Alpha one Drive with a 21 pitch prop. and between 30 and 40 mph the 383 sipped 3.5/3.7 gallons per hour. I like that, but I know that I am prob. heavier and have twin screws. Also can you tell me now to put pics. in the Thread.

The only way you can post pics if you are not a paying member is host them with a site like www.photobucket.com