Duo-prop v. single

smvorca350z

Looking at 2 identical boats (29' 10' 6" beam), ea with  2, VP 5.0 GXi motors, one has Duo props & the other has single 3 blade (not sure of size or pitch) props.  Looking at the spec sheet the twin props offer about a 3 mph increase at same fuel consumption. 

The boat with dual props is about $12k more and most other criteria between the two are similar.  Are there any other significant pros/cons to one or the other & is it worth the extra $ for the duo props?

MarkB

One minor thing ... a single prop has a tendancy to turn the boat to one direction. A dual prop offsets each other so it keeps the boat straighter. This will only be noticed at low speeds (idle, no wake).

Michael T

IMO the duo props are worth the money for the performance they will deliver, particularly if the boat is loaded-up. The 5.0 is, IMO, a small, small block and the Bllls will add needed performance. I can not be more specific about performance as I do not know the make and model of the boat you are considering.

NavyCTRC

duoprop boat will get on plane faster and stay on plane at lower speeds.  all of the differences between the boats you describe will be in the "performance" category. If it was just a few thousand difference, it would be worth it.  12K is a big difference.    there are thousands of pocket cruisers with single prop outdrives that get along just fine. 

LaRea

Sounds like the second prop saves you 10% on fuel.  Do the math ... how long will it take to offset the $12K?  Not long, if you use the boat a lot.  And you'll have a boat that goes faster, planes better and docks easier.

Michael T

.....and then there's re-sale some day. Buyers are starting to expect counter rotating drives.

Dream_Inn

For $12k difference, depending on what the single prop drive is (B-2?), you can change out the lower unit and replace with a counter rotating drive.  I know on my B-2 drives (single prop), you can change the lower unit and make them B-3s.

@MT, it all depends on the boat.  The larger boats tend to go much better with a single prop.  It's mainly because that single prop is much larger in diameter.  Mine goes like a dream with the single props.

jme097

Don't the BIII's offer better maneuverability at docking as well than the older single blade drives?  I took my buddies 98 Vista out last year on a calm day and it was almost night and day when it came to pulling in the slip when compared to mine. Who knows, maybe it was in my head lol

wm61356

I have Bravo 2's on my 320 and it performs very well, however my choice for the boat you are looking at would be the duo-prop setup. The duo prop set up will help improve efficiency and should be a good performer coupled to the 5 liter engines that the boat is equipped with. One caution that I have is to stay away from the VP XDP Duo-prop drives. VP XDP's are known for water intrusion at the driveshaft bellows. Even after several recalls and revised part releases from VP the issue was never resolved and repair costs to try to fix the issue are quite high. VP discontinued production of those drives after a relatively short time. You didn't mention the year of the boat in question or what model drives it has so I thought I'd mention the XDP issue just in case.

rasbury

I would agree with the difference at the dock. The only other boat I have had was a 20' bow rider with a 4.0L alpha II- backing was night and day between the two- would for sure say my 270 handles much better than the single prop hands down, was amazed at the difference.

Michael T

Can't agree @ DI I have never been on any model of cruiser up to 40 feet that performed better in any manner, handling at low speed, getting onto plane handling at high speed and fuel efficiency that didn't perform better with Bllls. IMO single prop for any pleasure boat up to 40 feet is old technology. I have been on a 2013 Rinker EC 400 with 502's and BlllXR drives and it blew the cr*p out of any Rinker 400 with Blls that I was ever on - in every respect. I think you need to get out more DI.... LOL

NavyCTRC

MT, not sure about big cruisers, but on smaller boats BII drives are faster than BIII's because the surface area on all those blades creates more drag.  That is why go-fast boats almost exclusively use BII's or single prop drives of some sort.  But I agree with you!  Duo-prop and BIII's outperform single props on cruisers for all sorts of reasons, mostly backing up and getting on plane faster are the biggest benefits.

Dream_Inn

@MT, LOL!  you are certainly all about power, more power.  I agree with you on typical cruiser boats, which is what is being talked about here.  The 2 counter rotating props are great!  Had it on my 310 and loved it.  But when you get to 40 ft, there is a lot of weight and that big prop can really dig in.  I cruise probably close to a dozen times a year with two other 400/390 boats that have duoprop (one has diesel with Volvo duoprop, the other gas with B-3s).  Not really much difference at all.  Heck, we've had all 3 of us take off together (what a sight to see) and we really all got up to speed at the same time.  It's interesting you said you were on other 400s with B-2s.  I haven't really seen any others.