Dont forget the 485/935 Yanmar, which Im told is closer to 500hp.

Theres the 500hp yanmar which when rated with a reasonable fuel temp is actually at 485. This engine produces 1100lbs of torque.

Then there is the 6ly3 which is the 480hp engine but it is rated with about 940lbs of torque. It weighs in at about 1400lbs and peaks at 3300rpm. I would say it is as close as you will get to a fast spinning light weight reliable engine with close to 500hp. Prop setup is very critical as well as some good tabs in order to spin lots of prop and still get out of the hole with this type setup.

Yanmar is known amongst diesels as light and high-revving at the expense of more torque at low rpm. Typically you give up a good bit of top speed because a similar HP engine (ex yanmar 315 vs. volvo d6 310) will make more power down low and take more prop.

Same boat with a yanmar 315 or volvo 310 the volvo spins much lower RPM for the same cruise speed, more top end speed and similar if not better hole shot. The trade off is weight, its a good bit bigger and heavier.

If you are looking at modified truck engines which are lighter and more powerful than the equivalent offering from yanmar I would be wary. Yanmar has pushed the envelope and then found the happy medium to create a reliable but reasonable size/weight, push much farther and you'll be making a very expensive mistake.

Last I checked a new 6ly3 lists at around $40,000.

Do I see some Weissman gearboxes specially built for Duramax?

http://www.jaylenosgarage.com/video/...l?vidID=100933

Great 9 min. video. That would make another great project.

Agreed. Look at the horsepower ratings of these light truck engines, when installed in the heavier truck lines. They are always detuned for longevity. For instance, the Duramax is 360 hp in the pickups, but detuned to 300 hp in the larger Kodiak and Topkick lines.

Michael

For the same reasons the Chevy 496 gasoline engine doesn't make 700 horsepower, light duty mechanicals, insufficient volumetric efficiency (bad breathing), and inadequate fuel system.

Michael

Do you by chance know anything about a tune for my 6ly3's that is coming out in the next few weeks..

Dont forget that with a diesel in a performance boat what you really want is a torque curve that is the opposite of what you need in a truck as you dont need the torque rise as the revs drop like you do when you go up a hill.
So when the manufacturers lift the torque curve up the rev rangefor a boat engine, HP being a function of rpm, also goes up.
Now peak Volumetric Efficiency is also peak torque so can the engine breath well at the new rpm that you require it to produce peak torque ( turbos can mask some of this )
I think this is why some great truck engines just dont make great boat engines.
You cant just go and buy your high flow race heads and cam for a diesel....or can you?

You cant just go and buy your high flow race heads and cam for a diesel....or can you?

Sure you can, check on the Cummins tuner sites, these guys are making some pretty neat stuff.

have you seen the small high (relatively) reving diesels out of switzerland - they drop in where chevy big blocks already are - they even use the same wire harness.....little light on HP for now but coming along.http://www.perfprotech.com/store/Art...l-engines.aspx