I see listed in various locations on the net about the 6.5 marine engine that gives you 300 hp. While our engines seem to be limited out at about 195. Now, I see that there is differences in injectors and pumps, but is that it? Do they have a different block and crank or something that can allow them 300 hp without blowin to bits?

They typically use the 18:1cr pistons - allows more Boost without incurring more pumping losses, allows increased fuel for more power.

'Course, they have the entire lake, or bay, to provide adequate cooling at full power.

Street engines are seldom at full power, so the heat is manageable.

Normal street use sees normal temps, load temps are lower because additional Boost lowers EGT's and ECT's.

Diesel engines are more efficient at 'lean' burn conditions - total combustion is assured where fuel charge is consumed before oxygen charge is depleted.

Lean doesn't have same connotations as with gasoline combustion - just means adequate oxygen to fully burn every last atomized globule of fuel on every power stroke.

Also lowers emmissions - won't see any black vapors behind you.

Tree-huggers will love you for that.

(Also, good persuasive argument for justification to the significant other);)

So, how 'bout de block? Is it the same block as our street diesels? or are they some kinda space-aged-super-titanium alloy of some crazy sort. I see your posts on the original design only calling for ~135hp. How in de world does the block hold together at 300hp?

Where traceability was available, broken blocks could be related to 1.) turbocharged, and 2.) harmonic balancer\drive pulley deterioration

Broken cranks could be related to turbocharged and 1.) at second main journal - harmonic balancer\drive pulley deterioration and 2.) at 4th main journal - dual mass flywheel deterioration.

Either type of breakage could, but not always, result in three center mains webbing cracking out of block

Three center mains could crack out of block without damaging crankshaft.

Where traceable, crank\block damage could be related to failing\failed harmonic balancer.

'92-'93 -599 block is supposed to be best among the older series for hop-up.

'97-up block with piston-spray oil galleries along pan-rails is supposed to be the worst.

The new 2001-200X blocks from AMG\GEP are supposed to be over-all best, redesigned for longevity.

All years are bad - all years are good, except for the '97-'99 oil-spray blocks.

It would appear that pulling the pan and inspecting the pan rails is the best method of determining good or bad - if the harmonic balancer is in good shape, and the mains webbing does not indicate any cracking, then you have a good block.

Marine-use and stationary Diesel engines - long-term, fairly constant rpm - are subject to less, and much different, stresses than a street engine.

For street (racing), balanced and Tuf-Trided crank, block machined for splayed mains caps, close attention to harmonic balancer seems to keep things together.

For street hauling power, balanced crank and close attention to harmonic balancer seems to work.

Both types are out there, in various types of service, chalking up the mileage.

But, no - nothing exotic, beyond the recently new blocks from AMG\GEP.

And, remember - you do not hear about all the ones that do not break......

I've read about splayed mains, so what are they?

The pan rail\mains webbing is machined to take new, wider main caps, with inner pair of bolts - closest to crank - in original location.

The two outer bolts are angled outward - splayed - and the block is drilled and tapped to accept.

The original outer holes are filled to prevent collapse.

The inner bolt pair clamping force is straight down, the outer pair clamp at an angle, which helps hold the sides of the block crankcase together, stabilizing the mains webbing.

Which stabilizes the crankshaft, such that no angular movement offsets piston travel.

It is done, in this case, to help hold the block together.

Ok.
Here is a silly question, is the harmonic balancer\drive pulley the same thing. That is the pulley on the front of the crankshaft?

Also, what is a dual mass flywheel? How can a flywheel deteriorate? :)

The harmonic balancer hub is mounted on and bolted to the crankshaft, to the tune of 200ftlbs.

The accessory drive pulley hub is bolted to the h-b hub, via four bolts.

Both have rubber-isolated components - the rubber deteriorates with ozone, heat, oil spills, torsional stress, etc.

You'll see the pulley, with the drive belt around it, and the harmonic balancer directly behind.

The dual mass flywheel is a two-piece unit, with the harmonic shock absorber ring being rubber-isolated from the main flywheel, which is attached to the crankshaft.

Purpose was to absorb the various shock-loading of the engine\manual transmission power train.

The rubber components deteriorate from heat, ozone, torsional stress, and any oil leakage from the rear main seal, or fuel spills from the filter area, etc.

Makes a loud rattling noise at idle.