Single or Duoprop

[Tafflad]

I have owned several runabouts .... in the 20' range.
These are typically ~19' hulls with an overall 21' length incl swim platform.
My current being a Monterey 194FS

I only have a V6 MPI as that provides all the power I need for recreational kneeboard/wakeboard/skyski

I always fit a Tower and and a correctly matched High Five prop ...............that gives me huge increase in pull for the low speed starts.

Starting the search for next boat ...............

The ones I am looking at offer the drive in twin contra rotating props Volvo or Mercruiser......... I have never owned one of these ... are they worthy the extra cost ? the manufacturer blurb says all the right things for me, better acceleration, better torque, better tracking ............ all things I want, not interested in higher top end speed.
Have read that unless your engine is >250hp then the extar weight will cancel out any benefits ...


Welcome comments from those that have or have had these.

With a standard prop you spend time checking WOT to get the right pitch, does this not apply to 'duoprops' do they come matched by manufacturer and that is that ?

 

[alldodge]

I have owned several runabouts .... in the 20' range.
These are typically ~19' hulls with an overall 21' length incl swim platform.
My current being a Monterey 194FS

I only have a V6 MPI as that provides all the power I need for recreational kneeboard/wakeboard/skyski

I always fit a Tower and and a correctly matched High Five prop ...............that gives me huge increase in pull for the low speed starts.

Starting the search for next boat ...............

The ones I am looking at offer the drive in twin contra rotating props Volvo or Mercruiser......... I have never owned one of these ... are they worthy teh extra cost ? the manufacturer blurb says all teh right things for me, better acceleration, better torque, better tracking ............ all things I want, not interested in higher top end speed.
Welcome comments form those that have or have had these.

With a standard prop you spend time checking WOT to get the right pitch, does this not apply to 'duoprops' do they come matched by manufacturer and that is that ?

DP and Bravo 3 setups are the way to go. They can make an under powered boat respond better. A correctly powered boat will respond even better. Have run both for many years and currently have one of each. You cannot beat a counter rotating prop for coming out of the hole and fuel economy. A really great thing is backing up. A single prop makes the boat go sideways when backing, the twin prop is "almost" straight, not quite but much better. Only down is the twins are heavier so you need help removing and installing the drive, and if you want to run above 50MPH they start to slow you down.

Don't know what you mean but checking WOT. You can have issues with your high 5 prop with to much lift and it grabbing air. If you had a standard 3 blade prop you wouldn't have the same issue

 

[Tafflad]

>"Don't know what you mean but checking WOT"

To get the right prop pitch you need to know the WOT ratring for your engine and make asure that boat can get to that rating and not over or under in terms of rpm, which running too l ow or too high a pitch will cause.
Just wondering if you also have to do same pitch matching exercise for a 'duo prop', or whether they are installed matched correctly to engine/hull by manufacturer.

 

[alldodge]

>"Don't know what you mean but checking WOT"

To get the right prop pitch you need to know the WOT ratring for your engine and make asure that boat can get to that rating and not over or under in terms of rpm, which running too l ow or too high a pitch will cause.
Just wondering if you also have to do same pitch matching exercise for a 'duo prop', or whether they are installed matched correctly to engine/hull by manufacturer.

Props are props, doesn't matter if it is one or two. When a boat is designed the manufacture puts a prop or props on the boat to meet WOT and best performance. The only time you run into the need to change the pitch is when the boat is being used for something other then designed. Changes can be from the owner wanting more hole shot and less top end,. Like going from the standard 21 pitch to a 19 because it comes out of the hole quicker, but the down side is the engine will over rev. For the best setup you always want max WOT range +/- 200 rpm

 

[Tafflad]

So in the case of duoprop ... I would be right in initial comment that they would be matched to achieving WOT by the manufacturer.

Unless I have missed something you do not get a variation in duoprop deign ... 3-blade, 4-blade, 5-blade etc. .... or from Aluminium to Stainless so no need to ever change the pitch it should be matched.
To change it would take you outside of WOT operating range.

 

[alldodge]

So in the case of duoprop ... I would be right in initial comment that they would be matched to achieving WOT by the manufacturer.

Unless I have missed something you do not get a variation in duoprop deign ... 3-blade, 4-blade, 5-blade etc. .... or from Aluminium to Stainless so no need to ever change the pitch it should be matched.
To change it would take you outside of WOT operating range.

This statement is answered by not necessarily. A manufacture in most all cases does their home work and finds a setup that works. The setup includes weight, hull design, engine hp, drive ratio and prop for a given boat and it's intended use. Many manufactures will also use a cheaper prop to keep the price down for sale. Prop design is a complex issue which include rake, diameter, blades and materials. The prop that came on the boat is the general prop which will work and others may increase top end of take off slightly. Putting a 5 blade prop on a boat will allow for quicker hole shoots and increase lift to get the hull out of the water. The down side of a 5 blades on a boat not designed for it, meaning if the boat is not designed for the stern of the hull to be at the surface of the water. With the high lift prop the boat is lifted to the point the prop will ventilate.

So yes changing props do change hole shot and top end of a given boat for a given situation. If your WOT is 4800 RPM and your running just under it, another prop can get you closer to the top end, but this may also change the hole shot. A change will increase or decrease areas based on what your trying to achieve. The DP/B3 prop sets come in 2 variations, 3 and 4 blade configurations. The latest is the 4 blade twin props. There is plenty of advertising which states the 4 blade is better then the 3 but not actual side by side with same configuration.

I have two props for my Rinker, a 21 3-blade for running around and cruising. When I use to pull several skiiers at one time I would change to a 19 3-blade for hole shot. The 19 would give me all the hole shot I needed but I would over rev the engine at WOT.

 

[Tafflad]

My boat is only used for watersports .. so I don't need to 'change' props for different work .... on every boat I have had, I have changed to SS prop, tried many variants, but for me the High Five best meets the needs. ( the pull and low speed planing capability)
My contemplation at this time is whether to pay extra and get the DP/B3 ....so I was trying to ascertain if I order one would they come matched for WOT, so I would not have to look to change.
Assuming that SS DP/B3 sets are not cheap.

I founs some test reults of identical boat side by side ... one with DP the other not .... certainly more efficient and better acceleration.
The only disadvantage I can see is cost ... to buy - or if the blades strike something, or if you want to boat above 50mph ... which I don't.

i was not aware that there are 3 or 4 blade variants .. so will need to look closer at that.


Is there any big difference between DP and B3 ... read that there were corrosion issues with older B3 (now fixed by mercathode ) if you trailer your boat - as I do, then there is no issue anyway ... it was electrolysis between large stainless blades & aluminium gear-case.

Never owned a Volvo ...

I am interested in the new V6 250hp ..... sealed cooling system, it has all the power of the 5.0L in the weight saving V6 package.
Plus I do not want a V8 ... simply not needed for use I put boat to.
Maybe one day Mercury or Volvo will get around to a suitable marine diesel sports engine .. the marine version of the VW GTI diesel, is lightweight, loads of power, free revving and lots of low down torque ........... all the things recreational boaters could benefit by.
Plus I could get marine diesel that is significantly cheaper to buy.

 

[alldodge]

DP and B3 all come with stainless steel props. I know of no current prop manufacture which makes a set from aluminum. Merc is making the B3 with a 4 blade forward and a 3 AFT. Both companies make a good product, I stick with Merc because I know them and parts can be found all over the place. Prices for parts are also cheaper.

As far as diesels, they are on the way, there are a few more out there this year then a last, but still for mostly larger boats (above 21ft).

As for corrosion, stainless causes corrosion, and the more you have the more possibility of it happening. Both Volvo and Merc have and have had similar issues. The Mercathode has been around for a very long time and Volvo uses something just like it but calls it something else. The big issue here is if the boat is connected to shore power, which yours is not, it's trailered. So this is a non-issue for your self

 

[Scott Danforth]

Is it worth the extra $ for a dual prop drive - yes

I own an older volvo DuoProp, and I absolutely love it. I run two sets of props, one for watersports, and one for cruising. Then again Im pushing over 24' of boat. I have a warmed up 5.7 liter currently and will be going stroker soon, so I disagree with the >250hp statement

both Mercruiser and Volvo have nice dual prop choices, with the benefits indicated being absolutely true. Volvo props are a bit more expensive than Mercruiser props, however I prefer the Volvo drive slightly to the Mercruiser, so its a trade off.

PCM has been providing the VW/Audi based V6 and V8 diesels in ski boats and wake boats for a while now. great power plants. If you can get the V6 diesel in front of a dual prop drive, you would have a killer drive train in an I/O.

 

[JoLin]

I've owned both types as wel. A single engine boat with a VP Duo-prop, and two twin-engined boats with single prop drives- a Volvo and the current Merc.

On a single engine boat dual props have a big positive impact on the boat's handling, particularly in reverse. Prop/torque steer is nearly eliminated. On the twin engine boats, I actually use that same prop steer to maneuver the boat via the engine controls. I seldom touch the steering when backing, as I can swing the bow or stern any way I need to by shifting the right drive into the right gear at the right time.

From a performance perspective, I do wish I had the duo's. My 27' Four Winns (V-6 Volvos) and the current boat (V-6 Mercs) would both benefit from the extra 'oomph' they provide comng out of the hole, and better midrange efficiency.

In your case (single engine, V-6 boat), I'd go with the duo's in a heartbeat if I could afford the price difference. You'll get better hole shot and easier handling. It's a win-win. There are pros and cons to both brands (I personally prefer Volvo), but I think ether will do you just fine.

My .02

 

[bruceb58]

I would never own another sterndrive boat without a duoprop.

 

[Tafflad]

Thanks guys .... all positive ... only negative seems price