Velvet Drive possible dumb question

[Bigmako286]

Jango I have a question for you I have a 1989 286 mako with twin 350s merc with velvet drives and the boat weight is 8000.what prop size should I be running? thank for any help you can give .
Capt. Dave

[Jango]

You need to provide gearbox ratio , Also is 8000# with fuel, gear and normal passenger load? ----- Jango

[Bigmako286]

Thanks for your response ! The gear box is 1.52.1 and the 8000 is bare boat with no fuel and no gear added .I also use my boat as a six pack dive boat or fishing trips.
Thanks Capt. Dave

[Jango]

Assuming your Engines are 350 cu in and 270 HP. Figuring 9500 lbs w. 270HP @ 4400 rpm Motors, 1.52 gear, Prop calculates to 16 x 15, 3 blade - 55% D.A.R. Max speed 31 knots, with cruise around 23 K.
Higher displacement would require larger Dia or higher D.A.R ( 4 bladed props ) with 14 Pitch.

Hope this Helps ---- Jango

[Bigmako286]

That helps quit a lot !! Thank you so much.I will take a look and see
What needs to take place to get the props pitched correctly.
Capt. Dave

[Jango]

Forgot to mention;
Make sure your motors are in tune and the Boat Bottom is clean (not fouled). Also the 16 in.Prop Dia is important - don't go smaller.

[Bigmako286]

Thanks Captain.
See ya on the big Blue!!

Captain Dave