Marine diesel
 

Is there a special outdrive for diesel engines? Beefier gears and different ratios since diesels turn lower rpms in thier optimum ranges?
Would an outdrive that was originally mated to a 350 work effectively ( I know diesels turn less rpm than gas and have more torque) with a diesel. Will the outdrive handle the torque?
If not, Can anyone reccomend a diesel and outdrive setup for a 2800 lb 22ft. craft? Prefer turbo diesel. I hear VW has a new sweet marine 6cyl turbo diesel.

Re: Marine diesel
 

95 through 465hp Cummins engine/Mercruiser drive matched sets, or
110hp through 375hp Volvo diesel/Volvo Penta drive, or
105 through 450 Yanmar diesel/Mercruiser drive sets, or
185 & 220 hp BMW diesel/BMW MkII drive.

The Cummins/Merc setup will give you access to the most service points, and the Bravo drives are very reliable.

I also found mention of 220 & 310 hp Mercedes diesel engine/OMC drive combos being sold in Australia.

The only mention I could find of a Volkswagen diesel/stern drive combo suggested that the VW would be mated to a Volvo drive in the future and available in a 80 and 120hp config.

Can anyone else find more info?

Re: Marine diesel
 

I did some research an d found the VW is avail in 165 HP and 225 HP mated to the bravo . The numbers on the example boats(specifically 20-22 ft boats) were impressive in terms of speed and fuel consumption. look at the WOT and Cruise Ranges and fuel consumptions , look at the speeds WOW !
http://www.vw-m.de/index.php?id=172&L=1&tx_prisreferenzboote_pi1[view]=details&tx_prisreferenzboote_pi1[uid]=35&tx_prisreferenzboote_pi1[amotor]=9&tx_prisreferenzboote_pi1[dstart]=10
I also discovered Ring Power is distributing and servicing them.

Re: Marine diesel
 

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.

Re: Marine diesel
 

In your opinion is that good economy in respect to gas I/O and Outboards ? Seems double or even triple compared to an outboard of same or close HP. remember this is thier 225 HP take a look at some of the 165 HP boat references.

Re: Marine diesel
 

First, that is not an apples to apples boat. Ski boats are usually flat in the back, have alot less wet hull area, and run on flat lakes, not the open ocean, compared to a 23' seacraft. IMHO, you could probably get close to the milage in a 4 stroke outboard, all boats being equal. I think that type of inboard would give you a little better milage (10-15%), and the outboard would give you better performance, it's a tradeoff, that's just my opinion.

Re: Marine diesel
 

VolksVagon just dosn't sound "badass" enough to be married to a beauty like a SeaCraft ;). I'm sure its a good product though :D just my 2 pennies

Re: Marine diesel
 

If gas wasn't 3 bucks a gallon, I have a 426 hemi that would probably move a seacraft along just fine, and sound even better.

Re: Marine diesel
 

Lake Pipes and all!

Re: Marine diesel
 

What kind of diesel do you want to put into what kind of boat. The lower end-powered diesels won't harm a Alpha sterndrive, but the upper end stuff is creates too much torque for a alpha and require a Bravo class drive.

Volvo makes the best drives although I'm not sure what series of drives can handle certain diesel power, but I'm inclined to say I prefer a volvo drive to a merc drive.

That said, my Grady White Sailfish has twin Cummins Mercruiser 1.7 DTI 120 HP a piece diesels mated to Alpha X drives. So far so good, but those drives are actually reinforced Alpha drives (they are called Alpha X drives)

Basically it is feasiable with great reliability, but you need to make sure the drive can handle the power.

Re: Marine diesel
 

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.

Re: Marine diesel
 

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.

Re: Marine diesel
 

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 :D

Re: Marine diesel
 

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

Re: Marine diesel
 

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.

Re: Marine diesel
 

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

Re: Marine diesel
 

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.

Re: Marine diesel
 

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.

Re: Marine diesel
 

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

Re: Marine diesel
 

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! :D

Re: Marine diesel
 

I have seen 3.7 mpg on a 23 with a single engine cruising at about 27. I don't think you will get past 4 mpg with an outboard. The difference is, the same boat has a wot of 48, where most diesels won't go much past 35.

Re: Marine diesel
 

Gradysailfish. Do you have a 25' grady? Was it an i/o new or did you do a convert? What is your cruise mph/burn and top speed? I have heard those 120's burn next to nothing but vibrate pretty badly. I saw the motor drive combo quoted for about 11 grand.

I am guessing your burn combined about 7.5gph at 25mph. Am i in the ball park?

Re: Marine diesel
 

For the question of different outdrives....I know the Bravo I has a different top cap for diesels....it has cooling fins on it. There could be different internal parts as well.