IPS versus V-Drives comparison test

Dave S

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TECHNICAL Contributor
Oct 3, 2006
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Upstate South Carolina
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This is an interesting test comparing two Formula 45's back to back. One is equipped with more powerfull engines and V-drives while the other is equipped with IPS drives. The IPS equipped boat is the clear winner with some pretty dramatic results. I wonder if Zeus will perform as well. Here is the article. http://www.boattest.com/Resources/view_news.aspx?NewsID=439
 
That's what I'm talkin' about!
 
BoatTEST.com testing found that in the Formula 45 --

The IPS version weights about 1700-lbs less
The IPS model costs $19,620 (MSRP) Less that the V-drive model
The IPS system has 280-hp less, total, in the twin installation
The IPS version has a WOT speed of 37.9 mph on our radar gun vs. 36.2 (5% Faster)
The IPS burns at cruise 31.5 gph vs 46.5 for the V-drive version (33% Less)
The IPS has a cruising range of 320 miles vs. 217 miles (47% more range at 90% tankage)
The IPS has the Joy Stick which makes everyone look like a pro and keeps marriages together

http://www.cmdmarine.com/ftp/zeus/
 
Were the cruising speeds the same for both?
 
The concept is sound

Surface drives and jet drives have all been trying to get to the point of propuslion within the laminar flow of water over the moving hull. Prop shafts with down angles of 14-18 degrees are wasting a tremendous amount of enegry torqing the hull up instead of forward.

The word is Cummins will announce a all Cummins IPS system in Mid 2008. Unfortunately, IPS will not be a practical repower solution for current sub 60 footers as designs for the ER hull structure is totally different.

Next boat ... maybe. We'll see how Neptune takes to this idea over the logn haul.
 
The numbers are pretty hard to ignore in addition to the space gained by the use of IPS. Even if the numbers where identical the ease of control with the joystick makes it more desireable.
 
A 30% fuel economy advantage? 30%??

And both designs are basically using PROPELLERS to drive the boat? The benefits claim just doesn't sound right.

I am not naysaying the benfites of PODS. . . I think the directional control has significant advantages. . .but one has to wonder about the how you get such dramataically improved performance considering that the mechanism of propulsion is similar.

Can it POSSIBLY be because of the angle of thrust? If so. . .that would imply that the advantage of IPS would tend to disappear in I/O boats, which can be trimmed for optimal drive angle. It would also imply that I/O boats would have much better fuel economy than comparable hulls with V drives. . .which I don't think is the case.

Can it possibly be the screw arrangement? I note that the pods seems to have the duo prop arrangement. To me, that doesn't seem quite right. Afterall, boats with BIII drives are not inherently more *efficient* than boats with BII drives.

I think application of Occam's Razor would suggest that these numbers are cooked in some way. i.e., the 45 with conventional drive had a few funky cylinders that both robbed power and fuel economy.
 
comsnark said:
A 30% fuel economy advantage? 30%??

And both designs are basically using PROPELLERS to drive the boat? The benefits claim just doesn't sound right.

I am not naysaying the benfites of PODS. . . I think the directional control has significant advantages. . .but one has to wonder about the how you get such dramataically improved performance considering that the mechanism of propulsion is similar.

Can it POSSIBLY be because of the angle of thrust? If so. . .that would imply that the advantage of IPS would tend to disappear in I/O boats, which can be trimmed for optimal drive angle. It would also imply that I/O boats would have much better fuel economy than comparable hulls with V drives. . .which I don't think is the case.

Can it possibly be the screw arrangement? I note that the pods seems to have the duo prop arrangement. To me, that doesn't seem quite right. Afterall, boats with BIII drives are not inherently more *efficient* than boats with BII drives.

I think application of Occam's Razor would suggest that these numbers are cooked in some way. i.e., the 45 with conventional drive had a few funky cylinders that both robbed power and fuel economy.

30% is about right - bear in mind that they downsized the motors 280 HP.

I/O's do have about a 30% performance advantage over V-Drives (just a little less).

BIII's are more efficient than BII's, though not that much.

All in all, I think the data is spot on.
 
Hampton said:
30% is about right - bear in mind that they downsized the motors 280 HP.

I/O's do have about a 30% performance advantage over V-Drives (just a little less).

BIII's are more efficient than BII's, though not that much.

All in all, I think the data is spot on.

Thank you. I appreciate the insight.

So. . .simply converting the angle of thrust is a majority of the *fuel economy* benefit. By this logic. . .we should all have I/O drives on boats this size.

I understand that they were using smaller motors with the pods. WHY? I presume (and this probably a good thing) that if the pods are that much more efficient, then you can get away with smaller engines.

This still implies that the pods will yield LOW advantage in fuel economy vs an I/O drive boat.

- - - - - -

Which brings me to my main point: If this type of engine arrangement is SO much more efficient, why does everyone poo-poo all over I/O drives in 35 foot boats when V-Drives start to be available? Nobody quotes performance advantages of the I/O. But everyone does talk about the maintenance problems of I/O drives vs V-Drive.

So. . .looking at this drive -> how much more complicated is this drive than a B-III drive? To me, it looks a HECK lot more complicated. Duo prop arrangement, and lots more flexibility. I suspect in 3-5 years, the tech will advance enough that reliability will be ON PAR with BIII units.

So if "conventional wisdom" is to go for V-Drive over I/O, then why would you pick IPS over I/O? The only advantage that I see is Maneuverability of the boat.

Which of course. .. .is a big deal. Is it really that much better than V-Drive and a bow thruster.

(By the time I can afford such a boat (probably never), I would get the IPS system.
 
Comsnark,

You can't leave I/O's in saltwater!!!!!!!!!!!!!!!!!!!!!!

In a 340 such as mine, there wasn't a decision to be made. Besides, there are two things that I am glad to be rid of - my I/O and my trailer - they were each more maintenance than my boat and motor, even though neither ever failed in 10 years.

So, you take the efficiency of an I/O, the maintenance of a V-Drive (I hope), and the maneuverability of a tugboat, and you've provided the drive for my next boat.
 
Hampton said:
Comsnark,
You can't leave I/O's in saltwater!!!!!!!!!!!!!!!!!!!!!!

But Hampton; exactly how are these "pods" any different than a BIII I/O drive? It seems to me that these are basically I/O units mounted UNDER the hull instead of BEHIND the hull.

Mind you. . there are probably HUGE advantages having these pods under the hull from a maneuverability perspective; but I *suspect* that's where the advantages over I/O drives end.

From a corrosion and maintenance perspective, I imagine that these pods are pretty much equivilent to BIII drives.

It is quite possible that the materials and whatnot are superior to what is used in a BIII drive. If that is the case (one certainly hopes so!) then you could also apply the technology to a BIII drive. Wouldn't that be sweet? That could really be important for the trailer boats (I am not sure how you would trailer a boat with a POD under it).

In terms of internal complexity, you are still transmitting engine force to a propeller that does not have a fixed geometry to the engine. And the pictures show a duo-prop. The mechanical internals are probably quite similar to a BIII drive.

BTW: I imagine the desire for a bow thruster doesn't change with the pods, unless one of the pods is at the bow. Sure, you can push and pull the stern in all sorts of crazy ways -> but if a 15knot wind is yanking your bow, the bottom line is that you either need to PIVOT the boat with reversed engines or you need a bow thruster.
 
At least the MC Zeus version has the props behind the housing, facing back unlike Volvo IPS which has the props facing forward.

I cant imagine the amount of prop damage this would create,
theres plenty of posts in here about hitting debris already.
 
comsnark said:
Hampton said:
Comsnark,
You can't leave I/O's in saltwater!!!!!!!!!!!!!!!!!!!!!!

But Hampton; exactly how are these "pods" any different than a BIII I/O drive? It seems to me that these are basically I/O units mounted UNDER the hull instead of BEHIND the hull.

From a corrosion and maintenance perspective, I imagine that these pods are pretty much equivilent to BIII drives.

It is quite possible that the materials and whatnot are superior to what is used in a BIII drive. If that is the case (one certainly hopes so!) then you could also apply the technology to a BIII drive. Wouldn't that be sweet? That could really be important for the trailer boats (I am not sure how you would trailer a boat with a POD under it).

I am with Comsnark on this one... what is the difference... thinking my next boat will be in the range that does not offer v-drives, but such that trailering is not really an option, I will be docking at the coast. Would like to see more info on this subject.
 
There was a question about if I/Os are like IPS and are both so much more efficient, why don't boaters choose I/Os much more often than an V-Drive?

There are a couple reasons. I'd just like to point out that I/Os and IPS are not that much alike in design. I see the main commonality in that they have a steerable prop with no ruddder.

First, in a heavy sea an inboard balances the boat better, with the engine amidships instead of in the stern. The props are beneath the hull and are less likely to cavitate in heavy seas.

Second, maintenance. An inboard system has lower maintenance requirements for the in-water gear. You don't want to be hauling larger boats all the time because it's expensive. It's possible to do more work in the boat in the water with an inboard drive.

Third, power. Until fairly recently I/O drives did not have the power to drive larger boats. Improvements in design and materials have allowed sterndrives to be practical in larger boats.

Fourth, risk. Think about the multiple bellows on a I/O drive. Do you want to risk your million dollar boat sinking from a leaking bellows? The rate of failure doesn't change from a smaller boat (except comparing single- to multi-engine setups, but the risk is greater because the boat costs more.
 
Some info from the Volvo IPS FAQ section.

What’s the difference compared to sterndrives?
The drive units are of bronze and stainless steel, rather than aluminum. Combined with the placement under the hull, out of the sun, means reduced risk of marine growth. Service requirements are lower for IPS.

I'd say this is a major difference between I/Os and IPS. Less risk of corrosion, and there is no bellows.

Why pulling propellers?
Pulling propellers work in undisturbed water giving better efficiency than rear-facing. They are farther away from the transom – minimising the risk of cavitation. Pulsation from the propellers is minimal, reducing onboard sound levels. There is also no need for hull tunnels and a flat surface V-hull can be used – always the most efficient and economical solution.

The push vs. pull debate will probably go on forever, but I don't see a pulling prop arrangement as bad. If you are hit something in the water, I don't think it much matters which way the props face. You'll still need prop work done.

What kind of propellers are used?
The specially developed and systematic Volvo Penta T-series propellers made of nickel, aluminium, bronze-alloy.

How much service is needed?
Service requirements are low, compared to inboard shafts and sterndrives. Apart from standard engine service, the oil in the drive unit needs changing every two years. No glands to change, no propeller shaft alignments etc.
 
comsnark said:
Hampton said:
Comsnark,
You can't leave I/O's in saltwater!!!!!!!!!!!!!!!!!!!!!!

But Hampton; exactly how are these "pods" any different than a BIII I/O drive? It seems to me that these are basically I/O units mounted UNDER the hull instead of BEHIND the hull.

Mind you. . there are probably HUGE advantages having these pods under the hull from a maneuverability perspective; but I *suspect* that's where the advantages over I/O drives end.

From a corrosion and maintenance perspective, I imagine that these pods are pretty much equivilent to BIII drives.

It is quite possible that the materials and whatnot are superior to what is used in a BIII drive. If that is the case (one certainly hopes so!) then you could also apply the technology to a BIII drive. Wouldn't that be sweet? That could really be important for the trailer boats (I am not sure how you would trailer a boat with a POD under it).

In terms of internal complexity, you are still transmitting engine force to a propeller that does not have a fixed geometry to the engine. And the pictures show a duo-prop. The mechanical internals are probably quite similar to a BIII drive.

BTW: I imagine the desire for a bow thruster doesn't change with the pods, unless one of the pods is at the bow. Sure, you can push and pull the stern in all sorts of crazy ways -> but if a 15knot wind is yanking your bow, the bottom line is that you either need to PIVOT the boat with reversed engines or you need a bow thruster.

Corrosion:

The anode consists of a titanium plate coated with ceramic that is protected in a rugged housing injection moulded from DuPont Zytel 75LG40HSL. The resin is made up of polyamide (PA) 66 polymer reinforced with 40% by weight of long glass fibres and is part of the DuPont SuperStructural Solutions portfolio. Mercury Marine injection moulds the housing and assembles the anode at its moulding facility in St Cloud, Florida, USA.

The robustness of the anode allows it to be mounted underwater on the hull, close to the boat’s propeller and drive train. The housing is hermetically sealed to the hull, and the anode is connected electrically by wire to a power source within the boat and to a reference electrode placed at a calculated distance away. The anode has already been used as part of the Zeus™ drive for large diesel-powered craft from Cummins-MerCruiser Diesel, a joint venture partnership of Cummins Inc and Mercury Marine. It is claimed that in the future, the anode could be used to protect inboard or outboard marine drives of any size or power.

“The DuPont material allowed us to develop an anode that can perform and endure fully immersed in a conductive and corrosive underwater environment,†says Scott Olig, polymer engineer, Mercury Marine. “In addition to having inherent corrosion resistance, it meets needs for high load-carrying capacity, resistance to abrasion or impact damage by sand, grit or underwater objects, stable dielectric properties and ability to hold exacting dimensional tolerances.â€

Stern Drive Compare and Bow Thruster:

Zeus is a highly advanced propulsion system that delivers a proven level of safety; up to 15 percent faster top speed, up to 30 percent better fuel economy, unsurpassed handling at high and low speeds, vessel systems integration unparalleled in the marine industry and increased power density up to 550 horsepower.

Some of the most notable benefits from Project Zeus for boaters will be experienced at the helm. Around the dock, our intuitive joystick control eliminates anxiety. Underway, the automated trim control feature simplifies operation. In addition, Skyhook Electronic AnchorTM, a component of our highly advanced Precision PilotTM system keeps a Zeus equipped vessel on a fixed heading within a tight area, even in strong currents and windy conditions. All of this technology was developed with a goal of simplifying the boating experience while maintaining safety.

Culminating 15 years of development, building upon technology advancing designs, Zeus incorporates a familiar looking, yet totally new pod with counter-rotating stainless steel, rear facing propellers and a through hub exhaust. Independent vectoring for each pod delivers dramatically improved high-speed handling. Docking is easier than ever. These steerable pods, along with an advanced joystick control system deliver precise turning and tight maneuvering that is far superior to bow thrusters.

Efficiency and additional features:

The “torpedoes†leave the water relatively undisturbed so that the props grip with -maximum efficiency. As a result, both high-speed and low-speed handling are dramatically improved. Trim tabs are integrated into the pods.

Zeus-powered boats track true and respond instantly to helm commands. At low speeds, Zeus steers with a joystick that directs pod thrust for precise maneuverability. The driver is actually able to crab the boat sideways or pirouette in a tight circle. But the advanced technology doesn’t stop there. An intelligent station-keeping system reads GPS coordinates and directs thrust to keep a boat in position without the driver having to touch the wheel or controls—that’s a very handy feature to have when waiting at a busy fuel dock or for a berth to become avalable.â€
 
Wow. The truth is almost lost in all that marketting mumbo jumbo, isn't it?

From reading the blurb, it seems like much of the "experience" is thanks to fancy electronics ("Skyhook Electronic AnchorTM, a component of our highly advanced Precision PilotTM system" - what da' blazes is that?.) Also, note the reference to an automated trim control system, and the fact that trim control is achieved via the pods.

Note the repeated reference to "15 percent faster top speed, 30 percent better fuel economy" -> presumably better than to a V-Drive.

And the references to the Anode covering is intruiguing. Note that they are not saying that the pods are electolytically a non-issue: they are saying that they have a good anode system.

I see that B_arrington found information stating that the Volvo pods are Brass and stainless, thus minimizing corrossion. And the reason the BIII drive doesn't isn't built this way is. . . .cost?


- - - - - - - -

It should be interesting to see where this technology goes over the next few years. I bet this is just like when cars switched from carbs to fuel injection. Greatest thing since sliced bread -> once you get the kinks worked out.

- - - - - - - -

There are a couple reasons. I'd just like to point out that I/Os and IPS are not that much alike in design. I see the main commonality in that they have a steerable prop with no ruddder.

First, in a heavy sea an inboard balances the boat better, with the engine amidships instead of in the stern. The props are beneath the hull and are less likely to cavitate in heavy seas.

Second, maintenance. An inboard system has lower maintenance requirements for the in-water gear. You don't want to be hauling larger boats all the time because it's expensive. It's possible to do more work in the boat in the water with an inboard drive.

It would be interesting to see how IPS changes boat designs. I need to do more reading; but on the surface it seems like if you are MOVING THE ENGINES, then you are changing the basic design of the boat, right? How is this handled on boats that have both V-Drive and I/O options -> Are the engines moved significantly? Or is one option inherently suboptimal (i.e., the boat is designed one way; and the "other" option results in a less well balanced boat).

The note about caviation in rough seas is very sound.

I wonder what the real maintenance requirements of the IPS are. There are gears and whatnot in this drive just like in a BIII drive. Do we really think this maintenance can be done without removing the drive? I suppose you could get at it from the top; but I suspect that the engine would be in the way.

BTW: I personally am not a huge fan of the BIII drive. When I was boat shopping, I really liked the idea of getting Twin Alpha's rather than a single BIII. The BIII just 'seemed' too complicated. If I had to do it over again, however, I would prefer to get Twin B-I's (not that I had a choice). Much prefer to not have the water pump in the drive.
 
comsnark said:
Wow. The truth is almost lost in all that marketting mumbo jumbo, isn't it?
I see that B_arrington found information stating that the Volvo pods are Brass and stainless, thus minimizing corrossion. And the reason the BIII drive doesn't isn't built this way is. . . .cost?

There are probably a number of reasons why sterndrives are made from aluminum, and that cost is a major consideration. Bronze is a copper alloy, and copper is pretty expensive.

BTW, it's bronze, not brass. Both are copper alloys, but they have big differences in properties. I'm sure IPS uses some alloy specific to a marine environment, but I don't know any specifics.

I'd say that weight is also an important factor. Aluminum (and it's alloys) is generally much lighter than bronze. The molecular weight of Al is 13; Cu is 29. Since most bronze is about 88% copper, that's a big difference. Aluminum stern drives are heavy enough - I have to think a bronze drive would be much heavier. Since IPS is installed in pairs on bigger boats the increases eight is less important.

As for boat design and IPS, yes the boat hull has to be design to accommodate the setup. That's one reason why you didn't see more IPS-powered boats right away. It took some time for the marine architects to understand IPS and change the designs to accommodate it.
 

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