Re: dual outboard motors
I have had a twin installation and like them. That said, unless the boat is so big that it requires more horsepower than is currently available in a single engine, the negatives generally outweigh the positives. Most of the negatives relate to cost and performance. The simple fact of the matter is that twin installations are not as efficient as a single installation of the same horsepower.
You will carry more weight on the stern and burn more fuel, than you would with a single 120 hp engine. You'll also add the compexity of an extra battery, control unit, tach, fuel tank (unless you have one, large one now), fuel lines, etc. You will also have to change your steering system to accomodate a pair of engines, rather than a single engine.
Another thing that you will have to do, is to select the right pitch props for the new installation. You need to go to a higher pitch than what you have on the single engine now, but not so high that you can't plane the boat if one engine fails.
While your boat will go much faster than it does now, it will be slower than if you upgraded to a single, 120 hp engine, with the drag associated with two lower units being the main culprit. Your operating and maintenance costs will also be higher with the twin installation.
I would also plan on the possibility of having some problems related to torque steer and lean.
On the positive side, you will enjoy a certain amount of security that you don't get in a single engine. As long as you don't lose power in both engines due to fuel contamination, a log in the water, etc., its rare to have both engines fail at the same time. Increased maneuverability at the dock/trailer is also nice. If you ever do any towing and need to put the boat in a side tow for any reason, you will especially appreciate the ability to control the tow at low speeds, if you have two engines.
All in all, I would just evaluate the wisdom of the setup in terms of whether or not the boat will perform as it was designed and whether or not you can accept a higher cost associated with the twins.
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