Outboard propulsion: one or two engines? When the boat exceeds a certain size, choosing between one or two units become one of the first issues for the owner-to-be. It’s a matter of safety and performance on one hand, and lower costs of purchase and maintenance on the other hand. We had a conversation with Stefano Arrigoni, after sales manager of Mercury in Italy.
1. When budget is the priority
It’s the only case when going for a single engine is the choice. One 300 HP unit is cheaper than 2×150, while all the rigging is simplified, as normally the twin units have separate power and fuel systems to maximize safety. Add to that the maintenance cost, which for a 300 HP is just a bit higher than for a 150. Finally, fuel consumption at a certain speed is lower for the sole engine. The only economical advantage for the two, is that each unit is less stressed mechanically, therefore should last longer. But this is not enough to compensate the expenses listed.
2. How much is safety important?
If you’re a seaman you perfectly know: safety first. And nothing is better than two engines, as in case of failure of one unit, the second will take you back to the harbor. This, provided that all the rigging is doubled, including the battery cut-offs and the fuel dip-tubes. In the end, only the positive pole of the battery can be shared. That is why, you should always carefully check what lays behind a cheap offer for a double engine.
3. Is the type of boat a crucial aspect for the choice?
Maybe not crucial, but surely the kind of boat and her destination can be important factors. For instance, if she will be used mainly on a lake, the choice for a single engine can be smart. Same thing, if the transom is rather flat or small. On the contrary, when the Vee is deep and the main use will be on the sea, going for a twin set will improve performance and safety.
4. Is it important to choose the right propellers?
Whether it’s a single or a double mount, the propellers are very important and the topic would require a deep analysis. In simple terms, one engine needs more push than each of a pair, because a single prop has to work as good as two. In any case, installation of the engine must be very careful: not only the distance of the prop from the water surface, but also, in case, the gap between the two units.
5. On his ideal boat, what would Stefano Arrigoni go for?
There’s no doubt: double installation. Safety first, always, and if it’s a matter of budget, I would rather go for a smaller boat and save the money for two good engines. Mercury, of course…
Who is Stefano Arrigoni 37, from Milan, Stefano Arrigoni is with Brunswick Italia since 2003. He is now in charge of the after sales network for Mercury in Italy. He’s been dealing with any technical issues related to the mount of one or two engines, so he’s one of the best experts on the topic.