I've been pondering this all day, why don't diesels run as fast as gas engines in boats. It seems to me that with the tremendous torque of a diesel and the proper gearing and prop selection, they should perform as well as a gas job.

Glad you brought that up!!! I have been pondering this for some time too. I think they would be a much better powerplant. Ton of torque, and easy to increase power. With only a computer chip my F-350 has around 400 hp and 500+ lbs of torque. Do the injectors, larger turbo and exhaust and forget it!! There was a comparison done in Powerboat mag back in the summer between 2 Fountains, 1 with gas, the other with diesels and Arnesons. The diesel was equal, except $100,000.00 more!!!!! Plus it does not need a rebuild for 10,000 hrs.

My brother-in-law was going to repower a 1988 30' Checkmate with deisels. He said the deisel only weighs 160 lbs more than a big block.

I would love to hear more about deisels.

One problem is that they weigh alot. That alone will slow the diesel down. Another problem is that they have a very narrow power band. Most top out at 3k, many sooner. What that means is that a steeper prop is needed for speed which results in a very soggy bottom end. This is accentented by the use of turbos which won't spool up until the engine sees some r's. The cruiser guys like them because they don't care about the weight, and they like the TBO times. Besides, not many cruiser guys even know what a hole shot is.

I have bravo ones, whats a hole shot?

power to weight ratio.

In a 9000 pound boat, you add 1300 pounds for a diesel swap to 350 hp Caterpillars. You also can't use Bravos with them.

In an 18000 pound cruiser you add 1300 pounds for a diesel swap. You got v-drives or straight inboards and drivetrain durability is not a problem.

My Sea Ray was available with 330hp Mercruiser V-drive 454's that topped out at 34 mph (4500rpm), cruised at 22mph (3200rpm). Used 50gph WOT (both motors) and 29GPH cruise.

I got 310 horse Cats. Tops out at 37mph (2800rpm), cruises at 30mph (2400rpm). Uses 34GPH WOT, and 24GPH cruise. Runs just as hard with 15 people and full tanks as it does empty. Planes effortlessly (after turbo spool up), and never sounds like it is laboring.

Had to experience it myself before checking the option box for the upgrade - it was expensive.

I'll never run gas motors in a big boat again.

Performance boat?
Hard to overcome the power to weight ratio issue (unless you use questionable aluminum block Yanmars). The turbo lag is a real issue as well, but only coming out of the hole...


Other items: Diesel will not explode due to buildup of fumes...
Diesel will not silently kill you from Carbon Monoxide poisoning - yes it still puts out some CO, but you will wake up vomiting from the other comonents in the exhaust long before you will succumb to CO poisoning... Diesel fuel is usually cheaper than gasoline.
Diesels sound cool.

Bad? soot. gets everywhere, even on "sootless" new tech engines...

The Fountain with Yanmars and Arnesons? I think it is the coolest...

Ken, I know what you mean about the truck. I've got a 3500 Dodge with 370 horse marine injectors, "hot" fueling plate, 4'' exhaust.ect.....will run 16.2 in the 1/4 at 7900#. This is what lead me to start thinking about the diesel thing.
If I remember correctly didn't Fountain set a speed record with twin Diesel power?

I would love to see a 24HTM or 25-26Daytona with the MC 300hp diesel and bravo one package.

30" prop, 1.12 drive, 3500rpm = 88MPH less slip = 80MPH!

I know a guy with a 2002 Fountain 38 Sport Cruiser with Yenmar's and surface drives. Don't hold me to it, but I believe the engines are rated at around 415HP each.

Bottom line is this is a VERY HEAVY boat and he is running 68 MPH on GPS.

Not too bad when you consider all things.

I have also seen a 50 Foot Nortech with Diesels and if I remember right they are running over 80 MPH.

In my opinion we will start to see more diesels in performance boats in the years to come.

Just wish they could make them sound a little better. LOL

Sonic 30SS, My truck runs 16.3!!!

There are several new diesel packages available for offshore boats. Tremendous weight savings over earlier diesel options plus a much wider power band. And they come with outdrives. Merc is even offering one.