Sterndrive power is very popular in the Great Lakes, but not so popular in saltwater. This schism is probably because many sterndrive engines are cooled with raw seawater. In saltwater the seawater cooling tends to cause corrosion of the cooling system, particularly the exhaust manifolds, whereas in freshwater this problem is greatly reduced. Some sterndrives use a closed freshwater cooling system and a heat exchanger to the seawater.
There is a humorous and sarcastic observation about the real purpose of a sterndrive: to be a mechanic's annuity.
In regard to the performance of an OUTRAGE 25 CUDDY with a 330-HP sterndrive: the Volvo-Penta DuoProp drive is generally an efficient drive system, although the propeller set is expensive. Performance predictions would be similar with outboard engine power at the same weight on that hull. Using the Crouch method, I would expect the top speed potential to be
LBS= 5,500 (for weight I just added 1,000-lbs to the figure given above for the dry hull weight to allow for fuel, crew, and gear)
HP = 330 (I assume this is the power at the propeller shaft)
HULL CONSTANT = 180 (this is a well-know value for classic Boston Whaler moderate V-hull boats like an OUTRAGE)
Predicted top speed according to the Crouch method is then
MPH = 44
If the power is not rated at the propeller shaft, and if the boat were more heavily loaded, the performance would decrease. Here is another analysis
HP = 300
HULL CONSTANT = 180
MPH = 41
In either case, the top speed is likely to be very sufficient for use in the open ocean. I don't think you will be dashing around at more than 40-MPH too often.
As for fuel consumption, I would assume the gasoline engine may have a brake specific fuel consumption (BSFC) of about 0.55-lbs/HP-hour at maximum throttle. At full throttle and making 330-HP, the engine would then consume 182-lbs of fuel per hour. If gasoline fuel at a density of 6.25-lbs/gallon is consumed, then about 29-GPH is the fuel flow rate. If making 44-MPH, then fuel economy would be 44-MPH/29-GPH for 1.5-MPG. The actual economy will depend on the engine's actual BSFC, the propeller and drive efficiency, and other factors. But I would expect 1.5-MPG to be the worst likely fuel economy; it may be closer to 2-MPG. Note all my distances are in reference to statute miles. If you prefer units of nautical miles, you can convert them with a 1.1515:1 factor. At slow engine speeds (as used when angling) the engne BSFC is probably improved, and MPG would likely be better than older two-stroke-power-cycle carburetor outboard engines could produce.
If not familiar with these estimates, I explain the Crouch method
in another article. Use of brake specific fuel consumption (BSFC) is a standard method of assessing engine performance. A Wikipedia article may offer more insight on brake specific fuel consumption
The presence of that T-Top will tend to reduce performance from these calculations. Also, I don't think Boston Whaler ever offered a factory option of a T-Top, so the presumption I would make is that T-Top on this boat was added after it left the factory.
Some other comments:
--the closed transom of the sterndrive OUTRAGE would be advantageous in my opinion for use in the open ocean when angling, as in a following sea you would not be taking any waves over the transom as will occur with a notched transom boat trolling slowly downwind in some seas;
--the greatest liability with a sterndrive is the rubber bellows that keeps the sea from entering the boat at the transom via the large hole made in the transom for the sterndrive mechanism. Any puncture of the bellows brings seawater aboard. With the vast reserve floatation of a classic Boston Whaler 25-foot hull, this concern is somewhat lessened, but the integrity of the bellows is paramount to staying afloat;
--this particular boat has the Super Console, which some think is an advantage compared to the much narrower standard console; others think the console is too wide and impedes movement fore and aft in the cockpit. It is really a matter of personal preference.