Ahoy Gregg, Can I assume you are referencing the Volvo Penta 2003 model? Most of the original W-32's had the Volvo Penta MD2B. It is 67 cubic inches. I personally have owned two W-32's with the MD2B and travelled over 30,000 miles with it. Many went around the world. My average motoring speed was 5.3k. I could do 6.4k. Both of my boats performed identically. (After fairing the bottom, they would do 7.0k) The top speed that a W-32 can be expected to hit would be about 7.4k. On occasion, I thought how nice it would be to have about 10% more engine displacement/power. The Volvo 2003 is 78 cubic inches; that is 16% bigger. I have no long distance cruising experience with the 2003 model, but that 16% should certainly move a W-32 along at .25k faster than the MD2B. There are, or were, some W-32's out there with the 2003 Volvo, as I have seen them.
Only you can say whether the Volvo Penta 2003, at 78 ci, is not enough for a W-32. Personally That size engine would not be a deal breaker for me. I currently have a 91ci Westerbeke (Mitsubishi). It is more than adequate. Many people want as much engine as possible and I have installed a 132ci engine in a W-32. The bigger engines, weigh more, are bigger, and consume a little more fuel. The fuel consumption issue is usually not a big deal, but it certainly can be when crossing the North Pacific High, or voyaging around the world in very remote areas.
Engine size on a long distance voyaging boat has to be a compromise. Good luck with your choice. Keep us informed. Thanks, Dave