Duo-Prop, what's the scoop?

[nodigg]

A buddy is about to buy a used (2002) boat with a Duo-prop set up? How well do these things work in the real world? Oh, on a 23' Essex in particular. Don't they take away some speed, performance and reliabiltiy in relation say to a Bravo one?

[Havasu Hangin']

No. The Volvo Duoprop is a great setup (dependable). The only downside is that there are less performance parts available, if you want to "hot rod" it down the road.

[nodigg]

Are they not slower at top end given equal power and conditions? I always thought they were for underpowered boats that could not get on plane. Like the Advantage party cats used to be.

[LHC Kirby]

I have the Volvo Duo-Prop. It is on a 24' Mariah Deck boat. I love it, no it is not a speed demon, top speed is 50. I get real good fuel/hrs on it - seems like I can go forever.. The response I get at an idle, is real nice, backing is a breeze as well. the only thing I do not like - $1500 bucks of prop hanging out the back. I follow people alot! :D
I would get this set up again if needed!

[Ziggy]

My understanding is they give you a better hole shot with the added torque but take 50HP to drive, some loss at top end but insignificant if you have enough HP.
Down is I hear very little to hop 'em up....if that matters to you.

[nodigg]

I have the Volvo Duo-Prop. It is on a 24' Mariah Deck boat. I love it, no it is not a speed demon, top speed is 50. I get real good fuel/hrs on it - seems like I can go forever.. The response I get at an idle, is real nice, backing is a breeze as well. the only thing I do not like - $1500 bucks of prop hanging out the back. I follow people alot! :D
I would get this set up again if needed!
Oh yeah, forgot about that down side, two for one if you hit the rocks. I guess you would not get the torque steer with it though, that makes sense.

[nodigg]

My understanding is they give you a better hole shot with the added torque but take 50HP to drive, some loss at top end but insignificant if you have enough HP.
Down is I hear very little to hop 'em up....if that matters to you.
Well, this guy would NEVER hop up the engine so no problem there. If these take 50 HP to drive, I wonder what a Bravo one takes?

[Havasu Hangin']

The Duoprop (and Mercury Bravo 3 which copied it) were built to prevent slip (more prop in the water) and prevent torque-steer (counter-rotating props cancel each other out).
The damn outdrive always wants to go straight- go figure.
Because there is more prop in the water, there is more drag, which is why they are a little slower on the topend (maybe a MPH or two). Most manufacturers could solve this by raising the X-dimension a little, but they probably don't want to risk any blowout on a family (ski/wakeboard/tubing) boat.
In fact, the Mercury Blackhawk was a dual-prop surface drive (pretty much a shortie Bravo 3), but I think they had problems with the high-performance engines idling low enough to shift without killing the gears.
You see, cone clutch Duoprops and Bravo 3s have alot of prop in the water to be jamming in-n-out of gear, so a decent (low) idle is a must. So the low X-Dimension, need for a low idle, and no Volvo performance parts (and less dealers) make it tough to hot rod.
But for a boat that you are going to leave stock? Volvos are very durable- maybe even a better reputation than Mercury.
Just my non-expert opinion.

[nodigg]

The wife wants it Rick and it is within budget so I assume Dave will go ahead and agree to it. I agree he will never want to hop up the engine. Did you geta chance to see the boat by the way?
No, sounds like a good enough price though. I told her Thursday she ought to buy your boat as they need to just get it over with and go big enough for their family. I was just curious myself about the Duo-prop since it is not a big seller unless you are into the heavier pleasure boats.

[ECeptor]

In fact, the Mercury Blackhawk was a dual-prop surface drive (pretty much a shortie Bravo 3), but I think they had problems with the high-performance engines idling low enough to shift without killing the gears.
You see, cone clutch Duoprops and Bravo 3s have alot of prop in the water to be jamming in-n-out of gear, so a decent (low) idle is a must. So the low X-Dimension, need for a low idle, and no Volvo performance parts (and less dealers) make it tough to hot rod.
If someone really wanted to use a Blackhawk with big hp and a fast idle, they could set up an ignition kill system like the Alpha 1. It would kill the engine for just a second when the drive was engaged to cut power and rpm. I think it would be easy to make a home-brew system. Just need some sensors on the shifter for both fwd and rev, then an adjustable timer so you could tune it, and wire in to the lanyard kill circuit. Or you could just get a system of an Alpha 1...
I'd think the concentric counterrotating shafts and extra gears would make the blackhawk less robust. I know the B3 is the drive for big heavy cruisers, but it sure seems to make sense given a certain space claim one big heavier shaft would be more robust than two smaller ones.

[nodigg]

They know where mine is and if they wanted it they can buy it. They isn't going to happen though as Dave is firm on his budget.
Tell you what, anything less than 25 IMHO is a little small for them. The boys aren't done growing yet and they are already huge. Also, I am sure they would like to bring a friend or two aboard with them. Oh well...The Essex sounds like it is in very good shape. I think Dave is coming out Friday night to check it out. If you are out there you should try to go with him Rick.
I agree on the size thing, those boys are B I G! And their friends are big too! AND THE GRANDKIDS ARE GONNA BE BIG TOO! Lol! I think it best if Dave just let's Sheila make the boat decision. After all, what has he got to loose if she picks and pays?

[jbtrailerjim]

Are you sure it is a Volvo Duo Prop and not a Merc.Bravo III? Essex built a lot of 23's with the Bravo III set up on them and my guess this is what is on this particular boat.

[BADBLOWN572]

The counter roatating system is a real nice system if used in the right application. They reduce a lot of slip and have a real nice hole shot. If you plan on routinely carrying a lot of weight I would recommend it. The Carrera party decks used to use them pretty much exclusively on any engine short of a 500h.p. They roll the boat over a lot better to get on plane, drive strait, and are easy to controll. They do slow you down somewhat on top end, but if that is not a big deal, I would do it. Again, the real downsides to them are no upgrades on high performance parts and if you ever hit something, double the cost for repair on the props.
The Blackhawk drive was an attempt at a high performance drive and it worked awesome when it did. Like it was said, high performance motors killed the drive because the gears were not really up to par and would grenade when shifting into gear. The other problem was that the boats that had them had handling problems. Since the drive was a surface drive it didnt want to really turn on a single engine application and it didn't like to slow down because there really was no drive in the water to create drag. I do know that a company called Great American Concepts would lock the drive into forward and use a crash box in a twin engine boat. The boats were extremely efficient and killed anything with comprable power and hull configuration. Too bad Mercury scrapped the project and stopped development of high performance counter roatating drives.

[cola]

Hey Rick, out a little late on Sun. night. I hated to put the boat away. 23' Essex with Bravo 3 = nice set-up for a family boat. The top of the drive is the same as the Bravo 1 & interchangable.
Late, Mike

[ELVIS]

we have over 500 hr's on our bravo three and have no problems.

[nodigg]

Hey Rick, out a little late on Sun. night. I hated to put the boat away. 23' Essex with Bravo 3 = nice set-up for a family boat. The top of the drive is the same as the Bravo 1 & interchangable.
Late, Mike
Saw you cruising into Steamboat Saturday? but could not get your attention. Caught sight of you guys in the channel Saturday night on our way to the Turtle. What a great day on the water! (weekend)!

[nodigg]

Just quizzed a mechanic about the Duo-prop, he says basically the same thing. As long as you do not intend on adding horsepower, no problem. But in the event you have to pull the outdrive, it takes 4 hours as compared to 15 minutes for a Bravo one.

[BADBLOWN572]

Just quizzed a mechanic about the Duo-prop, he says basically the same thing. As long as you do not intend on adding horsepower, no problem. But in the event you have to pull the outdrive, it takes 4 hours as compared to 15 minutes for a Bravo one.
If you are talking about a Mercury Bravo 3, that is very incorrect. I can pull one in 15 minutes no problem. The B3 and B1 bolt to the same gimbal and have the exact same connections. The only thing that takes more time is that the drive is a lot heavier and often requires two people to line it up.
I actually demonstrated to a friend of mine how the Bravo style outdrives would be the #1 thing that I would steal if I were dishonest. If I am moving and the drive doesn't have external steering, 2.5 minutes and it would be off and in the back of a truck. I highly recommend locks for all bravo style drives!!! 2.5 minutes and I now have an outdrive worth 7k. That would equate to 168,000 an hour. Sounds like I am in the wrong business. ;) :D All Bravos are the same.

[Flying Tiger]

How are they for manuvering at low speeds and backing up?

[BADBLOWN572]

How are they for manuvering at low speeds and backing up?
better than any single prop boat. Their strengths are at slow speeds and manuevering.

[Beer-30]

I have not seen an Essex with a Vulva drive yet. That doesn't mean there isn't one in existance, but I have looked at a lot of boats. They almost always use the B-3 (Merc) on the 23 Monarch, and some of the time on their other boats. I have inquired about this multiple times from other builders, and they always respond with the same thing:
"It helps hide some inherent problems with certain bottoms".
Every one that I have got this from has not elaborated on this theory, as they are all very professional and don't seem to want to slander another builder.
Nodigg, I would find out about this if you can. I have heard this same thing from no less than 3 other boat gurus.
Other than that, most of the tests I have seen on other B-3 driven boats equates to excellent docking and slow speed behavior. Around 5 (+/- depending on boat tested) mph loss with the dual props. Most drivers related there was a slight "vibration" from the B-3 drive.
My big fear(s) are the extra spinning parts that drive the count-rotating shaft, and 2 props to buy each time instead of one. Plus, I don't like burning a certain fuel gph and going 5 or so mph slower than I could with another drive.
Just my take on it.

[nodigg]

If you are talking about a Mercury Bravo 3, that is very incorrect. I can pull one in 15 minutes no problem. The B3 and B1 bolt to the same gimbal and have the exact same connections. The only thing that takes more time is that the drive is a lot heavier and often requires two people to line it up.
I actually demonstrated to a friend of mine how the Bravo style outdrives would be the #1 thing that I would steal if I were dishonest. If I am moving and the drive doesn't have external steering, 2.5 minutes and it would be off and in the back of a truck. I highly recommend locks for all bravo style drives!!! 2.5 minutes and I now have an outdrive worth 7k. That would equate to 168,000 an hour. Sounds like I am in the wrong business. ;) :D All Bravos are the same.
I wasn't! I was talking Volvo Duo-prop.

[nodigg]

I am not surprised at this. Nodigg was probably talking to the guys who work on his boat....lol
JK Rick.....
Damn you been hard on me lately youngster! :boxingguy :confused: :D

[nodigg]

You have been an easy target the last day or two :) Go back to the Cheetah thread...lol
Maybe I just better duck back under cover! Hey, I called Barry, he would not send me a scetch of the new boat even! Guess I gotta drop by.

[Deano]

I have not seen an Essex with a Vulva drive yet.
:D :D :D :D

[BajaMike]

I will go by with you. Want to go this week?
Tom, did you order a new boat???
:confused: :eat: :2purples:

[Beer-30]

:D :D :D :D :D

[nodigg]

I will go by with you. Want to go this week?
Is he open on Sundays?

[Mardonzi]

We've got a pair of Duo Props hanging on the back of the boat and pulling one takes about 15 minutes,, One problem that we have been encountering with them is cavitation burns when we run aluminum props,,,
As far as performance, we cruise out at around 55 mph with an 11,500# boat and have no real problems with them...