There are plenty of things to think about when looking at outboard motors, including the decision between one or two. Some people will pick up two smaller outboard motors instead of a single larger one, reasoning that they'll still have one power unit if something goes wrong. That might be true, but modern outboards rarely suffer breakdowns. In fact, there are several more compelling advantages that come with sticking to a single outboard setup, and here are just four.
1. Lower Cost
Unless you get very lucky, picking up two outboard engines is going to cost significantly more than buying one outboard engine, even if overall horsepower works out the same. It isn't just the cost of the outboards themselves you need to think about – it's the installation. Having one unit instead of two simplifies power delivery systems and rigging. A more complex installation is going to be more expensive. Finally, you'll generally achieve stronger fuel efficiency when you use one outboard engine instead of two.
2. More Servicing
Having double the number of outboards means twice as much can go wrong. It's not necessarily twice as much work to service two outboards instead of one due to the fact that smaller engines require less oil, and you'll probably be dealing with eight cylinders instead of six cylinders. That said, it's still more work to keep two outboard motors running instead of just one. That isn't just inconvenient – it's also another factor that tends to make running two over one more expensive.
3. Added Weight
When you buy two outboard engines instead of one, you'll probably be buying two smaller units. Even so, you're almost certainly going to be adding more weight to your boat. This isn't as much of a concern as it used to be since modern outboards are becoming much lighter, but the weight difference between a single outboard and dual outboard is still significant. Added weight affects the craft's handling and balance.
4. More Drag
In theory, buying two 150 horsepower units instead of one 300 hp unit is going to provide the same speed through the water. In far, this is rarely the case. We've already mentioned the added weight, but what's more important is the added drag. The surface area of two outboard engines is going to be greater than that of one outboard engine. That means there's more drag through the water, which reduces top speed. As such, you'll probably need a pair of 170 horsepower outboards to match a single 300 horsepower unit.