Marine diesel

[nestorpr]

The Volvo website says that their DPS and XDP drives are designed to mate to high power diesels up to 225hp and their larger DPH & DPR drive mates to diesels in the 225-350 hp ranges.

For a Mercruiser you would need either the Bravo 2 or 3 models to take the higher torque of the larger diesels, the Alpha should be able to handle the lower hp models.

[3rdday]

I appreciate your opinion. Thanks Good point on the 4 stroke OB. with the diesel at 10-15% better economy, it would take a long time for the Return On Investment. Although it could be a lifetime engine.

[JohnB]

After thinking about some of the oil burners I have been on, a SeeVee in particular, I think at lower speeds, 25 mph or so, they might actually get quite a bit better fuel burn. The down side is weight. In a 23' boat, a diesel is probably about max weight on the boat. With all that weight, you have to push it harder to get more of it out of the water. I am not sure that 23' SeaCraft hull really performs it's best with that type of power. The inboards do ok, but it is a different kind of boat/ride. More like a ship, than a boat. They plow, rather than slice.
It's hard to explain, unless you drive one.
These new outboards are really starting to get some gas milage, but it takes a lot of gas to pay for a 15,000 motor.
From what I have seen, 25' of boat is the break point for going to twin outboards, or diesel. The advantage of the diesel is milage and low center of gravity. The advantage of the twins is speed and redundancy, while giving up balance and fuel milage. If there was a perfect solution, there would be only one kind of boat

[3rdday]

Very logical and well said. Thank you for the help and perspective !

[76Red18]

I'm paying $3.48 for a gallon of diesel and $3.05 for unleaded down here in S.W. Fl.. Haven't done the math, but maybe diesels' not the economical choice anymore.

[3rdday]

is that diesel off road diesel/ should be $ less... as it is taxed differently

[76Red18]

No, its at the pump but theres nowhere around here to get it in small quantitys. If you have a site prep or land clearing operation you can get a large supply delivered to a large holding tank. I dont have that type of an operation so I just pay at the pump for my trucks that use diesel.

[Fr. Frank]

They don't know how to do math on that engine.
WOT of 45 knots burning 13 gph is about 3.9 miles/gallon, not .29 and cruise is 5.8 miles/gallon. The range is off a tad, but at least it's close.

The quoted figure was gallons per mile, not miles per gallon.

WOT burn at .29 gallons per nautical mile is 3.4 nautical miles per gallon, or 3.9 statute miles per gallon.

Cruise fuel burn at .2 gallons per nautical mile is 5.0 nautical miles per gallon, or 5.75 statute miles per gallon.

[JohnB]

The quoted figure was gallons per mile, not miles per gallon.

WOT burn at .29 gallons per nautical mile is 3.4 nautical miles per gallon, or 3.9 statute miles per gallon.

Cruise fuel burn at .2 gallons per nautical mile is 5.0 nautical miles per gallon, or 5.75 statute miles per gallon.

Thanks for pointing that out, I always think mpg vs gpm.

[nestorpr]

With these numbers I don't know of any OB out there that gives 5+ mpg at cruise, does anyone? I think diesel is still the most economical way to go, and with the prices of OB's nowadays I don't think there's that big a difference in the "entrance fee" anymore. That plus the safety factor of diesel vs gas, the newer lightweight diesels (Volvo, Steyr, a new diesel being developed, see the Bertram31.com website), and computerized/common rail fuel systems have really made the new diesels very competitive in my opinion. I do like the ease of maintenance and "simplicity" of the OB's but, if I had the $$, I would still opt for a diesel over gas if possible. Just my $0.02!