THE GASOLINE INBOARDS on my last boat were based on a V- 8 design from 40 years ago, popular, I was told, in taxicab fleets. Robust to be sure, but they were also noisy, smelly, and reliant on the vagaries of the four-barrel carburetors that sat atop each block like carbon-smudged crowns. It may be a cliché, but one of the first things you notice while being around modern
inboards is, well, they start. As in the first time you turn the key, just like your car.
And that’s no accident, considering there are very few differences between the
engine powering today’s boats and the one in your light truck.
Our marine inboards have always shared a basic design with automotive engines. But
until recently, the biggest inboard manufacturers, Mercury Marine and Volvo Penta, relied
on blocks from General Motors that were a generation or two behind the times. That’s all
changed now. In a major departure from the status quo, Mercury announced in June 2014
that it would produce a block of its own design for the MerCruiser engines. Volvo went in
the other direction, and it began basing its designs on newer-generation GM blocks. These
two different approaches to the same problem – how to improve the boating experience for
those of us with gas inboards – can be boiled down to opposing beliefs.
“Six years ago, GM notified us it was discontinuing manufacturing the blocks that we’d
used as the basis of our engines for the past 20 years,” says Marcia Kull, vice president of
sales for Volvo Penta North America. “At that time, we needed to make a decision. We asked
ourselves, are engines more like a basic commodity, or are they an important component that
influences the boating experience?” Volvo Penta believes that all the engineering work and
technology built into those GM power plants pay dividends to boaters in measurable ways,
so the company moved forward using the very latest GM Gen 5 blocks.
Six cylinders, 250 horses, and zero
GM parts. Mercury designed its
new block from the ground up to
be a marine power plant.