Volvo IPS claims

[eyschulman]

For some time now I have been following the marketing and magazine test results of IPS equipped boats. My interest in IPS goes back 3 years ago when I was putting together the specifications for a 48 ft custom boat I was having built with multiple options for power and drive trains as considerations. I find it hard to get reliable feed back regarding the IPS system. Asking somebody who has just bought a new boat or who owns one is not necessarily a way to get unbiased information. Relying on magazine reviews even worse. Boat reviews like automobile magazine reviews have pretty much become a bonus free advertisement for the magazines advertising customers and rarely a disparaging word with emphasis on the positive. One interesting article came from the Hunt boat company where three of their production boats were built with different drive systems straight-jet- and IPS. A typical Volvo add as in a recent Yachting magazine states "a 40% longer cruising range,20%higher top speed and 30% reduced fuel consumption". I for one find it very hard to believe this. Is this set of values at one particular speed level or across the range? I have been comparing my 48 footer with twin straight drives to multiple published magazine test data of boats of same size beam and weight and consistently find up to 18k my fast cruise speed the IPS is not so good and often downright poor. What I am thinking is that IPS is good for a boat that almost always travels in mid 20K and higher speeds but a poor choice for people who with high fuel cost wish to back off on the fuel burn. How can a boat traveling at the higher speeds get a 40% longer cruise than one going one K below hull speed particularly if IPS is not efficient at the slower speeds?? So are there any readers out there who can confirm or with some real evidence disprove my skeptical opinion of the volvo add claims.

[DeepFrz]

Have you searched the internet?

[eyschulman]

What I have found on the net is sparse and the fuel advantage I see reports on are for high speed. Should my boat builder be advertising almost double the fuel economy because at 8K it is so? I am curious to know if others are aware of studies or real life experience with this highly hyped system who can confirm or cut off a little of the hype edge. As I mentioned above the hunt experiment was revealing. Are there other examples of comparison done by third parties who do not have an interest in selling volvos or boats with this system. The IPS system has become a major pivotal point for marketing new boats. The industry was and is in need of something to sell new boats and IPS has become a prominent selling point If your competition is selling IPS with all the hype, so do you.

[goboatingnow]

You must remember the primary point of IPS is to provide boat builders with a complete " drop-in " engine and drive train , the benefits to the user are. much more obscure. It's the exact equivalent to sail drives for yachts.

In my opinion conventional shaft drives , offer simplicity , reliability and user serviceability. Why do anything else

Dave

[DeepFrz]

I did a quick search and it looks to me like there have been some very major problems.

[downunder]

Originally Posted by goboatingnow

You must remember the primary point of IPS is to provide boat builders with a complete " drop-in " engine and drive train , the benefits to the user are. much more obscure. It's the exact equivalent to sail drives for yachts.

In my opinion conventional shaft drives , offer simplicity , reliability and user serviceability. Why do anything else

Dave

Whilst I agree with what you are saying I believe the boatbuilders are claiming improvements in speed with same HP. Some flowback there also with fuel economy.

As with you I like shafts.

[GPSocal]

I'm waiting for the first person experience report of an IPS owner hitting a deadhead at speed. Does the drive unit shear off and leave a small hole or get ripped out and leave a very large hole?

[goboatingnow]

Originally Posted by GPSocal

I'm waiting for the first person experience report of an IPS owner hitting a deadhead at speed. Does the drive unit shear off and leave a small hole or get ripped out and leave a very large hole?

I think that's been dealt with , the leg shears off

Dave

[Stumble]

Originally Posted by GPSocal

I'm waiting for the first person experience report of an IPS owner hitting a deadhead at speed. Does the drive unit shear off and leave a small hole or get ripped out and leave a very large hole?

The drive unit breaks off and the seals keep the water out. Last year there was a battlewagon that ripped both theirs off after hitting a partially submerged shipping container at 28kn. Other than a long slow tow in no real issues. Bolted on the new drive units and they were back on the water in 2 weeks (it may have been 3). Years ago we hit something and ripped both shafts out of a large Hatteras (my uncle was driving) and if not for the mud shoal would have sunk the boat.


I can accept some fuel economy advantage, but I don't know about double.

[eyschulman]

I did not bring up the potential maintenance and vulnerability issues. I believe they will be real for some and down the road resale may be affected as is the case for older stern drives. Of course volvo and the boat builders selling this system are not making claims in those areas. What I question is buying a IPS thinking it is going to save fuel and get you farther. If you are always running at high speed maybe but many boats just aren't run that way. I after my research and consultations including engineers who deal with pod drive elected twin straight drives for my 48 ft 34,000lb boat. My fuel burn is not extraordinary but respectable. 8K/4gal 9K/5gal 10K/8gal 15K/16gal 18K/20gal. Many boats reported in boating magazines of this size and weight with IPS do not do better often much worse. I do agree that the drop in installation and space saving and weight distribution issues greatly influence the builders but not sure they benefit the buyers.

[CarlF]

I had also heard whispers that the pod drives have not lived up to the marketing claims and that they only deliver the improved fuel efficiency at well above 20 knots. Something to do with the pod drag at lower speeds.

I just spent a few minutes looking around. The Cat-Zeus site is strangely quiet about the fuel economy savings. It says this:

Caterpillar pleasure craft customers enjoy the following benefits with the new Zeus® Pod Drive System:

• Clean, quiet, and comfortable. The pod drive system's counter-rotating propellers are mounted on large rubber supports for reduced gear noise and vibration.
• Enhanced maneuverability. The independent movement of each pod results in exceptional turning efficiency and amazing response.
• Safer by design. By mounting the pod in a tunnel, most floating debris is deflected downward, away from the propellers.
• Easy to install. The pod drive system is a complete package, requiring much less installation time compared to regular inboards.

No mention of fuel economy! It doesn't seem like something the marketing people would forget to put in

Then I found this PDF on the same site. It appears to say that there is no difference in nautical miles per gallon at any RPM between straight shaft and Zeus (except maybe the Zeus is worse around 1800 RPM)

http://marine.cat.com/cda/files/1132...%20Cummins.pdf

Am I reading this right?

[boatpoker]

Originally Posted by goboatingnow

You must remember the primary point of IPS is to provide boat builders with a complete " drop-in " engine and drive train , the benefits to the user are. much more obscure. It's the exact equivalent to sail drives for yachts.
Dave

Not quite "exactly the same". a few years ago I delivered a Regal 5560 with IPS from Toronto to Duluth MN. It was kinda fun to drive the boat around the harbour side ways. I don't think your sail drive can do that

[sabray]

What is the value of sailing around sideways?
I might pay more for a non Volvo natural aspirated diesel. Beta, john Deere or cummins .
Pretty cool for that brief docking moment. Otherwise I don't buy its value.
Someone has this and can tell us if they get better economy

[Richard_W]

How can a boat traveling at the higher speeds get a 40% longer cruise than one going one K below hull speed particularly if IPS is not efficient at the slower speeds?

Assuming that you are comparing boats with same characteristics (same hull and same engines), the other factor worth considering is engine operating characteristics over RPM range.

Two points for your consideration:

1. It is not unusual that higher HP/torque engine is more fuel efficient than lower HP/torque engine when moving the same heavy hull.

2. Many engines, especially gasoline engines, operates more efficiently in mid/high range than in low range of its RPM range. My big block gasoline Volvo Penta on my boat with my props, operates most efficiently in 1100-1200 RPM and 3200-3500 RPM ranges achieving 2.5 MPG. If RPM drops to 2000-2500 RPM the MPG gets below 1.5 MPG. These are based on instrument readings … GPS and FFM.

The long way of saying … yes, the higher RPMs can get you better mileage …

[eyschulman]

I believe what you are pointing out works for OB gas and smaller boats and some planning boats that have terrible mileage below plane in the range between hull speed and up over the hump. almost all motor boats do significantly better at or below hull speed. I agree that a boat built for and used routeenly at speeds of mid 20ks and higher can benefit from pod drive(not by much) but point out that that is not how most larger boats travel unless one owns oil wells or something like that.