HOW CAN I ACHIEVE MY BOAT´S BEST FUEL ECONOMY?
If you have not yet read Rule #1 & Rule #2, click here.
Reaching the longest Nm/l (or Nm/gal) – Rule #3 & Rule #4
Rule #3: Run your boat at planing speed (anywhere between 3000-3500rpm)
With a car we would say, run the engine somewhere between 1750-2500rpm in order to reach the optimal fuel economy because a big part of a car ́s fuel economy is affected by air resistance. The faster you drive, the harder the air becomes and the more difficult it is to drive through it.
At the speed at which the majority of sport boats cruise, air resistance is the least of the problems. The problem is how much the boat weights in the water (displacement), how much water surrounds the hull and how much water the boat has to displace in order to move. How do we reduce the displacement of the boat? By gaining speed. The faster you drive it, the harder the water becomes under the hull, the higher above the water the boat goes and the least resistance it makes around it. If you own a Monterey boats (as well as most north american boats) as a general rule you will find the optimal fuel economy planning at around 3000-3500rpm. This will allow you to reach the best Nm/L or Nm/Gal.
Rule #4: While running your boat at planing speed, lift up your boat’s bow (if the sea is rough the ride may become more uncomfortable, so adapt it to the weather conditions. Safety first!)
In “Rule #3” we spoke about how speed makes the water become harder offering less resistance on the hull. For the water to make even less resistance on the hull we will as well tilt the sterndrive to lift up the bow as much as possible at the same rpm mentioned before (between 3000-3500rpm). **always make sure the engine is cooling, and no cavitation noises take place at the transom**. Never tilt the engine more than 1/4th from the full down position.
Consuming the least L/h (or Gal/h)
The lowest fuel consumption will always be found at idle speed. If you want the tank to last as many hours as possible, you should be running your boat as close to idle speed as possible.
Summarizing the post, keep your hull clean, your engine properly serviced and always adapt your speed to your boating goals and weather conditions. For long distances (eg: covering 20Nm one way, or going from A to B, B to C and back to A), cruising speeds at around 3000-3500rpm will give you the best fuel economy. For long hours boating with a single tank without going anywhere, then keep the engine as close to idle as possible.
We wish you a fantastic boating day!
Don Marino Boats
