There are a lot of mixed opinions about IPS drives. I find it funny that some of the opinions (mostly negative) come from individuals who do not own, and have never owned an IPS powered boat. They just parrot back what they have either heard or read. I also happen to know that the majority of IPS problems occur after hitting an underwater object and not following Volvo Penta's repair procedures (you MUST check propellershaft runout after striking an object as a bent shaft will cause the seals to leak and put you in a world of hurt if water gets into the drive).
I can supply you with the following facts about IPS:
They are more expensive to service than either inboards or sterndrive units. The pods hold 4 gallons of drive oil each. They require a yearly change and the cost of the pod oil is about $70 per gallon. In a 2008 model, make sure the steering seal rings have been changed from bronze to the newer stainless steel upgraded versions. At the same time, also make sure that the drive unit oil pumps have been upgraded (along with the oil coolers). That covers the drive units.
Diesel engines also are a little more expensive to service. They hold much more oil, have multiple oil and fuel filters not counting air filters and crankcase vent filters.
Now for the pluses -
IPS is probably the most efficient drive system. My boat weighs about 23,000 lbs. It cruises at about 30 miles per hour and burns 20 gallons per hour (both engines). Top speed is about 42 miles per hour and burns a little over 30 gallons per hour (again, both engines). It tracks dead straight at idle all the way up to full speed. Because of vectored thrust (the pods turn), you have full directional control at idle speed.
Handling both underway and around the dock are fantastic. Waiting at the fuel dock or for a bridge opening is totally without stress. Because of the underwater exhaust, noise is lower than other systems and fumes or smoke is totally nonexistent.
