MerCruiser and Chevy: Marine Power Couple


Chevrolet small block

Millions and millions served: Chevrolet’s small block is the most prevalent marine powerplant on the planet, and for good reason. MerCruiser photo.

Look under the hatch and on the transom of most stern-drive runabouts and you will almost invariably see black, as in MerCruiser. And where there is MerCruiser, there is GM. But how did this come to be?

To approach an answer to that question, let’s look at what boat builders — and boaters, for that matter — need from an engine. Foremost, they need reliability and torque, and they need as much of the latter as they can get without sacrificing the former. They need tight packaging. They need parts availability and they need a wide service network to take care of customers after the sale.

Let’s start with power and reliability. Perhaps no other engine exemplifies those two watchwords better than the venerable small-block Chevrolet V8. Even if you have V6 MerCruiser power, you are benefitting from the simple design of the small block engine because the 4.3-liter V6 is essentially a V8 with two cylinders engineered away.

Introduced in 1955, the small-block engine has survived to this day with minimal refinements and design changes, and GM has produced — quite literally — millions of them. They were designed to be simple, because simplicity in an engine is a good way to achieve reliability, and because there are millions in use, parts for the small block are probably the easiest to source on the planet.

The simple V8 can reliably produce 300 horsepower in the form of MerCruiser’s 350 MAG ECT and run for years with little need for anything more than fluid changes and winterization. And it will do so smoothly and quietly with a catalyzed exhaust to reduce emissions. Turn the key and go.

(In fairness to Volvo-Penta, it too uses GM engines for its recreational applications.)

The small block does all that within a compact footprint. It’s the smallest V8 made that’s worth a darn. It’s shorter than the Ford small block by just enough, and we all know cockpit space on a boat is tight, so the less room the engine takes up, the more room for other things. Like beer.

That brings us to back to black, and that’s Mother Mercury. With more than 4,300 Mercury dealers in the United States and Canada, it’s easy to get black engines serviced. For comparison’s sake, Volvo Penta has some 1,200 dealers in the United States, which might help explain why MerCruisers are the dominant powertrain in most of the boats you’ll find on

So, is that the gospel of why marine power is the way it is? Well, not quite,  but the reasons I’ve listed are a big part of it, and, as always, I hope it helps you in your quest for that perfect used boat.



  1. Kyler Brown says:

    My grandfather has an old boat that hasn’t been used in years. I’m trying to fix it up so that I can use it. This article taught me a lot about engines, and I thought it was interesting to see the relation to Mercruiser’s and GM. I’ll have to check the engine on my grandpa’s to see if it was a GM one as well. Thanks for sharing this.

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