Single vs Duo Prop on Volvo Outdrive

dcartie

Seaman Apprentice
Joined
Sep 24, 2013
Messages
35
Hey guys, I am currently operating with a bayliner with a single 5.o mercruiser engine Bravo 3 and looking to change to a 2005 Cruisers 300 with two engines with 5.0 Volvo Penta with a single prop. It'll be used as a cruiser should, so top speed is not going to be needed. Backing into a slip in the marina is a concern as well. What's everyone's opinions/reviews and is it possible to change the single with a duo prop. (I doubt I will due to the expense), My concerns are planning, and getting good mpg, as well as backing.
 

Thalasso

Commander
Joined
Jan 18, 2011
Messages
2,876
Sx drives are basically the same as DPS-A's Only diff is the lower gear case. Not cost effective to switch over. Props alone are in the $700.00 range for the DpS-A
I would venture to say the lower unit is in the $4000.00 range (rebuilt) not counting core charge.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
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47,297
switching from SP's to DP's is common, however like Thalasso pointed out, can be costly.

however you are also going from a single to twins. backing anywhere is a breeze with twins. keep steering straight ahead and use the throttles and gears to back the boat. you can even spin the boat around.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
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fuel economy and boating do not go together
 

JoLin

Vice Admiral
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Aug 18, 2007
Messages
5,146
I've owned a single engine boat with VP duo-prop, and two twin engine boats with single-prop drives (one VP, one Merc). As noted, the cost of changing 2 drives over to duo-props is very, very high. It's highly doubtful that you'd notice enough performance improvement to warrant it - and any minor improvement in fuel economy would never pay back the initial cost over the life of the boat.

As for backing, twin single prop drives and their inherent propeller torque are your friend. Practice, practice. Learn to put the helm in the straight ahead position and keep your hands off the wheel. Use the engines/drives to steer the boat into your slip. Buy a Davis Rudder Position Indicator ($25.) and mount it on the hub of the steering wheel so you can be sure it's centered before you start backing.

Port drive in forward pushes the stern to port. In reverse it pulls the stern to starboard.
Starboard drive in forward pushes the stern to starboard. In reverse it pulls the stern to port.

You're gonna love it once you get the hang of it.

** As for fuel consumption, my bet would be 18 gph at cruise (mid-20's mph, 3200-3500 rpm) +/- 10%. Overall you'll get in the neighborhood of 1.25-1.5 mpg.
 
Last edited:

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Twin 230 hp 5.0s will use about 46 gallons per hour at wot.
Your drive train weight will be about double with twice the complication of a single.
It's my opinion that while a twin setup provides a spare in the event of a failure it
also very slightly increases the odds of a failure.
I have no experience with a twin setup but it would seem to me that it would require
a little more throttle to stay on plane of course you have the additional drag of the extra outdrive.
 

Reel-hip

Seaman Apprentice
Joined
Jun 1, 2012
Messages
40
switching from SP's to DP's is common, however like Thalasso pointed out, can be costly.

however you are also going from a single to twins. backing anywhere is a breeze with twins. keep steering straight ahead and use the throttles and gears to back the boat. you can even spin the boat around.


I second that ! Once you go with dual motors it will be easy.!
 
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