I have a 2001 3488 Command Bridge and want to know my cruising range. I have twin gas 5.7 liter Mercruisers with 2 barrel carbs.
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There are so many factors that result in the range of a boat, and they are about to cause you to do some driving. Since your boat has been in the water for some time, you may need to get a real-life answer to your question as opposed to one delivered by the owners manual. If you want accuracy be prepared to do some work.
Initially, I would suggest that you define "cruising". Top speed is only for short distances and since you are interested in total range one can assume you are looking for comfort and efficiency. On what waters do you safely and comfortably travel at what speed? Will currents be an issue? How big is the family? Load is always a contributing factor in fuel consumption. With different loads can you adjust the boat's attitude? Trim tabs solve this dilemma - they are a must in a boat of this size. Not only can you trim the boat to the load, but the tabs will help in the effort to get on top of the water.
Actually, on top is a misnomer since the semi-planing hull only semi-planes. But there is a point where you stop plowing water and rise up a bit and the bow comes back down. At that point or slightly above is your best range. At what engine speed does the boat plane? If you go just a little faster, can you back off on the trim tabs a bit and produce a smoother ride? Somewhere within this power band is the engine speed upon which you will calculate your fuel consumption. There are numerous ways to figure this out: either mechanically or mathematically. Many contributors to this site have an "app for that" Knowing fuel consumption and amount of fuel in the tanks will give you the ultimate range. Then back off at least 15% for safety sake.
Happy boating.
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