Join Date: Sep 2007
Location: Pasadena Md - Magothy side
Thanked 31 Times in 31 Posts
Rep Power: 12
Re: Bayliner Bucaneer Cruise Speed Under Power
Keep in mind that while diesels like to work, they like to work at no more than 90% continuously (recreational boats are fitted with either light or medium duty diesels, not the tug boat type continuous rated ones).
Your MD7A is rated at 13hp max at 2600 RPM. I'd not run it above 2340 RPM for more than 30 minutes.
If the Volvo and Bayliner engineers fit it out right you should reach your hull speed (
Your B 275 is 24.33 feet at the water line, max speed is 6.65 knots) at that RPM.
Volvo gives two different reduction ratio's - you didn't say you have the S drive (folder) so I'll go with the 1.91 ratio of the other model.
At 1800 rpm that's 942 RPM at the prop.
942 RPM * 11 inch pitch * .48 (standard slippage per Dave Gerr for a displacement boat) = 414 feet per minute - or 6.9 feet per second.
you guessed it 4.7 miles per hour
Funny how math just seems to work out isn't it.
At 2340 RPM
2106 rpm at the prop, 11 pitch = 926 feet per minute 15.4 feet per second ( 9 kts).
Since you can't go 9 knots, you are over pitched. Generally your engine came with a 14x9, just saying.
Lessons learned are opportunities earned.
Last edited by chucklesR; 01-23-2013 at 01:09 PM.