Sterndrive Engines: Big Block or Small?

The 454 Mag big-block inboard, mated to a MerCruiser outdrive.

The 454 Mag big-block inboard, mated to a MerCruiser outdrive.

I might be overthinking this, but let’s just say for the sake of simplicity that the price difference among all three is negligible, the hours are comparable, and that they all have a Bravo One drive. One has a 310-horsepower 454 big-block engine, another a 300-horse small-block, and the last one a 385-horse 454. How do you know which one is right? This is a good example, because the used market is well stocked with boats equipped with all of these engines.

Well, a lot of people might just shoot down the middle and go for the 310 horsepower big-block. No so fast. At 1,177 pounds with the drive, the big block is pretty heavy. The small-block propulsion package isn’t much lighter at 1,025 pounds, but it’s the better choice. Why? More power per pound of weight. The big-block in this example only has 10 horsepower to push around that extra 150 pounds or so.

It doesn’t sound like much, but the performance would be superior and the fuel economy would be better, too. I was never a fan of the 310 horsepower big-block, anyway. The internal components aren’t strong enough to handle any power upgrades.

That leaves the choice between the small-block and the 385-horsepower big-block, which is usually known as a 454 Mag MPI, and it’s where big blocks start getting good. For my money, I’d go with the big-block, but that’s for personal reasons. Every engine in every boat I’ve ever run has always become less and less satisfying the longer I’ve had it. With the 454 Mag MPI, it has the beefy internal components you need when adding power later. The 454 Mag MPI has the forged crank and rods, and higher flow heads than the 310-horse big block, so you can add a blower without fear of scattering the bottom end.

On the other hand, if 300 horsepower is plenty for you and your family, the small block is the way to go. It’s lighter and smaller, which also might mean larger stowage compartments under the engine hatch. Parts might even be cheaper because the small blocks were produced in greater numbers.

It might seem like I’m picking nits, but you’re going to have to live with the boat you choose for a while. It’s best to pick nits now rather than later. Of course, I might be overthinking it.

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