The test bed is this 100,000 lb. (45,359 kg.) luxury convertible sportfish built by Spencer Yachts. Can it attain any measure of a descent speed with roughly 18% less horsepower than the closest competitor? Will it burn twice as much fuel pushing more with less?
The plan was simple enough...
1. Create a boat that will show the world that large pod drives will work in luxury yachts.
2. Demonstrate that with less horsepower such a yacht will achieve respectable speeds.
3. Further demonstrate that said yacht will achieve superior fuel economy that will make it more than feasible for everyone else to follow suit.
4. Prove to big game anglers that a 100,000-lb. boat with pod drives can turn on a dime, back down, wiggle around and keep the stern pointed at the most spirited billfish imaginable trying every trick to break free -- and do it all better than any conventional inboard-powered boat on the market.
Now it would have been nice if a builder came up to Volvo Penta and said that they wanted to give this a try, but to no one’s surprise, that didn’t happen. The last time a builder of large yachts tried to experiment with a good concept was with diesel/electric engines and it was a miserable failure. Why would anyone want to spend millions in an attempt to put experimental pods in a large yacht to see what would happen… with the world watching?
Evidently, no one told Volvo Penta that diesel/electric story and they decided that if Mohammad wouldn’t go to the mountain, then they would just have to bring the mountain to Mohammad. They would have to have the boat built themselves.
The Project Boat – “Penta Gone”
When it came time to build their world class experiment, Volvo Penta needed a semi-custom yacht builder that could make a one-off, very specifically outlined yacht. The builder they chose was Spencer Yachts. With the passing of Palm Beach's Rybovich brothers, owner/designer/builder Paul Spencer is very close to claiming the mantle of king of sportfish custom boat building. And with Volvo Penta’s Spencer 70 “Penta Gone” he’s taken a giant leap further in that very direction.
Of course the main innovation of this yacht takes place in the engine room, not only in the newly designed engine/propulsion system, but in the very layout itself. Volvo Penta believes the new drive system is going to change sport fishing forever. Found there are three, brand new, state-of-the-art 13L, 900-hp engines that literally incorporate all the latest technology for maximizing performance, environmental friendliness, quietness, smoothness… all the attributes that the sport fishermen is looking for.
The engine room bulkhead has been moved a full 9’ (2.74 m) back providing more living space without compromising roominess in the engine room. Notice the space between the pods and the outboard main engines. Those white boxes house the house batteries - and the jackshafts.
The Big Pods
The third generation IPS-3 pods are the biggest units Volvo Penta has ever made to date and they specifically did so to move into the big yacht segment. Volvo Penta has enjoyed enormous success with IPS -1 and 2 in smaller boats.
The three generations of IPS. The number designators are not actual horsepower, but representative of the horsepower equivalent that is achieved with the pod drive system.
The list of innovations on this boat is, to say the least, lengthy. But let’s cover the highlights. First up is the installation of the pods themselves. We’ve demonstrated time and again how when there are pods installed in a boat it allows so much more living space because they simply don’t take up as much room as an inboard engine installation with a long shaft protruding out the back. In the case of the Spencer 70, they were able to move the aft bulkhead and the master stateroom further back a full 9’ (2.74 m). So in effect if you are standing in the master stateroom the foot of the bed is where the bulkhead used to be. Now there is additional space for an entire berth plus a head.
This is the outboard of one of the main engines. Notice how much room there is to move about. After two years of operation, the entire engine room is still as sterile as an operating room.
The Engine Room
Next we come to the extraordinary use of space in the engine room. Even with the bulkhead moved back 9’ (2.74 m) into the engine room there’s still an incredible amount of space. So much so that you can even walk around all three engines. Many of the ship’s systems need to be installed, but never need to be touched afterwards. These items are moved behind panels, out of the way, and out of sight. The front of those panels is then used for items that you do need to see: things such as display screens, touch pads, and the like. In all cases those panels can still be opened to reveal the tertiary items behind.
While it is necessary to have jackshafts running from the engines to the pods, it’s not necessary to waste the space around those shafts. At the two outboard engines, Volvo Penta custom built a box to go over the shafts. This is an incredibly clever use of space.
The middle engine on the centerline is low enough to be placed under the cockpit deck. The two outboard engines are higher because of the boat's deadrise, so must be pushed forward under the mezzanine seating and cabin.
No need for dual generators to take a dual space. In this engine room the generators are stacked one on top of another. Immediately adjacent to the generators is an array of fuel filters, 10 in all, two for each generator and two for each main engine. Ball valves will allow you to easily change the input between filters, so that you can effectively change filters on the fly. I notice these filters are mounted very close to the bottom of the workbench, but then I notice that the table of the workbench lifts right out for accessing the tops of the filters.
Notice the panel over the engine on the right. It houses the controls for the dual refrigerators and dual freezers in the cockpit.
Redundancy Makes Perfect
There are dual alternators on the two outboard main engines. Interestingly enough, one alternator is used for charging the house batteries as normal, the second is used for powering both the ships systems and the pilothouse systems. In this manner, the “Penta Gone” is able to continue running and get home in the event of the complete electrical failure of losing both generators, the entire AC System, and feeds from the batteries. For that matter, the pilothouse is basically a standalone unit. If it were possible to lift it off of the yacht, you could even drive it home if it had its own propulsion system.
On the left are dual stacked generators. Under the workbench are the fuel filters. Both gensets, and all the mains have dual filters that can be swapped out on the fly by turning the ball valves in between. Notice how the panel that the display monitor is mounted on can open revealing the rarely used components behind. On the right is the 240 volt panel.
On the aft bulkhead are exhaust diverters. These are connected to a clear wake exhaust system that eliminates bubbles from the prop wash which might scare fish off. Now, with a flip of a switch the wash behind the boat is cleaned of turbulence and bubbles. We will be sure to test the effectiveness of these exhaust diverters on camera.
Missing In Action?
To the practiced eye it was quickly evident that there were still some items missing in this engine room. It was just too open and there was just too much empty space. Sure enough, that initial impression was correct. When I mentioned this to Mike Meyer, a Volvo Penta consultant and one of the heads of the “Penta Gone” project, he simply smiled and escorted me to the forward stateroom.
Under the stateroom is a large equipment room that houses all of the missing items that neither need, nor want to be in the engine room. Looking around this compartment, it was easy to identify the water chillers, water makers, potable water tanks, and a second hot water heater. And since this is a pod driven boat, which eliminates the need for bow thrusters, the open forward section of this compartment is now used for storage.
Here is another view of the livewell pumps on the aft bulkhead. Notice how all hoses are perfectly double clamped.
Controlling The Beast
Now we come to the meat and potatoes of the “Penta Gone”. This is where the rubber meets the road as it were, and the entire reason for building this magnificent demonstration platform.
In the past, when I’ve been aboard a yacht of this caliber and class, it seems as if the builder was on a mission to make things as complicated as possible. In such instances, there are those among us who believe that this is part of the job security plan on the part of the captain, who typically has a hand in the design process. On the “Penta Gone”, the opposite is true. Not only was everything labeled to perfection in the engine room, but the operating systems were as straightforward as could be. It was the most elaborately laid out pilothouse I’ve ever seen, but it all came down to the control module at my right hand, and the joystick immediately adjacent.
It is the exact same control module that you would see on a 30’ (9.1 m) sportboat, with the same buttons and features, and the exact same joystick that we’ve seen time and again. The beauty of these electronic controls lies in the fact that there are no cables directly connecting the controls to the engine room. Instead there are wire runs to an electronic controller. This allows you to easily add control stations, a feature Volvo Penta exploited to its fullest on the “Penta Gone”. There is the main control station in the pilothouse and aft control station behind the pilothouse over-looking the cockpit, two additional control stations in the cockpit, and a fifth set of controls in the engine room.
Under the toolbox are the air chillers for the engine room. The boat’s chillers are located elsewhere in the boat. To the left is access to the crew’s quarters.
Finally The Test Begins
Departing the dock was simply a matter of engaging the joystick in low power mode, maneuvering the boat side to side as the crew casts off the lines, and ultimately pushing the stick forward to depart the slip. Once clear of the channel, and into the Intracoastal, we immediately came to a drawbridge that was set to open in 7 minutes. A single push of the “position hold” button on the control module was all it took to have the system automatically holding our position as we waited for the bridge. It was interesting to see how well the boat held her exact position, and heading, while those around us continually jockeyed for position in the following current… all without my having to touch the controls or the wheel.
Once we cleared the bridge the first order of business was to test the clear wake exhaust diverter. I went to the aft station, transferred control to that station with a push of a single button, and engaged the clear wake system with a push of another button. Sure enough, the turbulence that was immediately following the transom smoothed out into a clear, bubble-free wash. It literally appeared as if we had shut the engines down and we were now being towed through the water.
It did seem however, that the three engines were pushing us a little too fast for trolling at idle speed. True to form, by pressing one button, the trolling valves were engaged and our idle speed of 7.5 knots was reduced by half. Now we were in a trolling speed with a crystal clear wash behind us. I was starting to rethink my theory about these engines not attracting fish.
Still having the “keep it complicated” mindset, I began to add power to the throttles to see if the current setup would throw a curve to the uninitiated captain of the “Penta Gone”. Without any additional input, the exhaust diverter shut off at 800 rpm, and the trolling valves disengaged 1000 rpm. Just like that we were back to normal operation.
The Moment of Truth
Now it was time for the real test. Would this admittedly "underpowered" boat be able to make it to the coveted fishing grounds of the Bahamas, the middle grounds, or the canyons at the coveted 40 knots speed that sport fishermen crave? Would we burn twice the amount of fuel due to smaller engines having to work twice as hard? These were the questions running through my head as I advanced the throttles.
As I advanced the throttles to the stops we reached our top speed of 34.7 knots at 2300 rpm. There was no trimming, everything was being done automatically by the pods. Not surprisingly, we weren’t getting 40 knots. But to be fair, the fact that we we’re going this fast in a boat with a combined 2700 horsepower when normally it would’ve had 4000 to 4800 horsepower engines, was speaking volumes about the capabilities of these new pods.
But it isn’t just about speed, fuel burn is a critical factor. And fuel burn effects range.
Here you can see the exhaust diverters for the “clear wake” exhaust feature. The yellow hose is connected to a Hookah system. To the right you can just make out the aerator pump for the livewell.
As a point of comparison, lets look at another 70 foot sportfish convertible, this one displacing 116,400 lbs. and powered with the traditional twin 2200-horsepower MTU engines. That boat had a tested top speed of 36.3 knots with 4400 horsepower. And the fuel burn at WOT was 251 gph.
The Spencer 70 “Penta Gone”, with 39% less horsepower, was able to come very close to the same speed with a fuel burn of only 127.5 gph! That is 4.4% lower top speed and a 49% reduction in fuel consumption! We’re talking what could very easily be a difference of $5000-$7000 at the end of a hard day of running. On a six or seven day delivery trip from Florida to New England the difference could add up to $25,000 or more -- real money even for wealthy anglers.
Let’s do best cruise. Both boats seem to be reaching their best cruise speed at 1750 rpm. The MTU-powered 70-footer's cruise speed of 26 knots was achieved with a 138 gph fuel burn. By contrast, the “Penta Gone” cruised at 23.7 knots with a 77 gph fuel burn. That represent a 9% reduction in speed and a fuel burn reduction of 44%!
Obviously this isn't a lab-perfect head-to-head comparison, but about as good of one as you're likely to get in this size of vessel and the message here is unmistakable. Further, the percentage of fuel savings seen here is right in line with what we have seen when BoatTEST.com has been able to test the same model boat with both IPS and conventional inboard drives in smaller boats.
Take a look at the dual alternators on the main engine. Both outboard engines have this feature. One charges the house batteries, the second charges the ship's systems.
Dancing With Billfish
Performance figures notwithstanding, there was still one more test I had to perform. Volvo Penta chose to make their test bed out of the sport fishing boat, and in this league the captain’s ability to chase down a fish is as important as the catch itself. I headed to the aft station once again and transferred control. While enjoying a commanding view that more than encompassed the entire cockpit area, I faced aft and put both hands on the Palm Beach control sticks.
With sportfish mode engaged I shouted “fish on” and attempted to chase down my imaginary quarry. In this mode, Volvo Penta engineered the outboard pods to angle themselves outward, thereby giving a better bite for directional control. And it works! With the entire Volvo Penta senior executive staff watching, I got very heavy handed controlling their multimillion dollar luxury yacht in the wrong direction. Not only did I have complete, and previously unseen, directional control but I was also able to watch the GPS record 12 miles per hour while backing down! I pity any fish that this boat has to chase down.
Volvo Penta took a big chance at building the “Penta Gone”. The plan was to build a platform that demonstrated that pod technology will work in larger yachts. My test has shown that not only will it work, but it is actually an attractive proposition and one that deserves serious consideration on any new build. If the performance and maneuvering capabilities aren’t enough to convince you, then a simple glance at the fuel savings should do the trick. The “Penta Gone” may be the first boat with these new IPS1200 pods installed, but most assuredly won’t be the last.