Njawb

You mean these? Looks like a pretty cool answer to my lingering question about how to get rid of the gasoline requirement for a yacht tender.

HabanaJoe

I don't know who Cuyuna is but I have to tell you a light weight2 stroke style 6-71 with an overhead cam (high reving) and all the fancy electronics you guys talk about, roots blower with a clutch for low end power and that could be a winner - although probably not teir 3 compliant it would get the job done.

If you were to build from scratch that would be the great marine go-fast diesel????

At our OSNA factory I have 3 machining centers that do protype work from April to June as orders are non-existant for new product.

How hard to make one from the ground-up? Use 6-71 liners make a modular block use like a 4-71 crank, lightr the counters, cut the main and rod journals down in dia, re-harden and grind, make new rods - the head would be a problem to make with water cooling, the block is easy as water is just at the top of the liner, just make a hollowed out top section so the block is 3 peices in height from top to bottom. Center section being the air ports.

Another crazy thought (strictly a test stand engine for theory only), if we took a little 4 bangers gas engine, dual overhead cams, we could in theory use 2 exhaust cams and have both sets of valves flow exhaust - right? Change the pulleys and turn the cams at crank speed.

Could we punch through the block right into the cylinder with nipples and use that to inject our intake air into the cylinder and have a 2 stoke now?

We could machine injectors into the spark plug holes with common rail we don't need high pressure timed pumps right?

I understand that nothing here would be optimal but I think it could prove a platform to develope off of? Low unit volume off-road (race) engines can get away with teir 3 still, correct?

Your thoughts?

HabanaJoe

You guys are too funny "Steady Money"

The 903, 555, 504 were good engines nothing wrong just heavy with little power.

They sucked in a truck though, what a nightmare!!!!!

stainless

joe my point was fuel mielage of diesels in general vs gas and rpm range for the duramax vs the cummins.. sorry i ran the two points together... the rpm question comes into play with top speed issues in a cat more rpm = more prop speed the few people i know who tried doing a diesel mti didn't really seem to get big top speed #'s i would love to see a diesel work for this app. I thought banks had a duramax prototype at the miami show. it's on their website for supposed release later this yr or early next yr ?

dmaxx3500

i think you guys need to think in the 300-400 hp range, then theres alot less strain on the engines ,way less fuel consumpton,and they still make 700-1000 ft lbs of torque and can spin to 3000-3400 which is plenty ,

HabanaJoe

Stainless,

I might have read the two together, getting a little nuts with 5 kids (only 3 are mine) in the house today and my wife is out all damm day!!!!!

As for Banks we'll see what they release. That brings up another question, there is no problem to build a great hi-performance diesel but if it cost 3 times a gas engine and only last twice as long - it's a loser.

I think this is where we all get lost/caught up in our passions and beliefs about diesels.

There is a $ point where the diesel does not become a viable replacement for gas engines. Look at the gas pump, diesel is $1 a gallon more than gasoline!!!! So for every gallon of diesel you burn the payback based on maintance or fuel economy just keeps getting further away - it's nuts!!!

Your MTI refernces, is not based on engine rpm, look at the gearing they use to go real fast. They gear up more than they turn the engine faster. Gear ratios are pretty much unlimited so if you have the power you can get the output rpm you need to fly across the water.

I still stand firm on belief that people get all caught up in the "torque" thing and that it makes no difference what so ever, it's HP and how you apply it. You run the MTI with twin 1,200 hp gas engines and then you put a pair of 600 hp diesels in there with twice the torque and think the boat should go as fast if not faster???? You need HP to move the load, it is a measure of work performed and you need work to move the boat fast.

Joe Gere

HabanaJoe

dmaxx,

That is intelligent, your right, in the 300-400 (450?) range the Durmaxx can be a winner. At these 600-800hp numbers I think their kidding themselves?????

But it the same thing, it will only replace a 400 hp gas engine not a 600 hp gas engine.

HaxbySpeed

Horsepower is a byproduct of torque and rpm. The guys talking about two speeds are on the right track imo. If you can take advantage of the diesels huge low rpm torque and convert that into propeller speed rather then having to spin the motors to 4000 plus rpms the effieciency and durability can be fantastic. I have done a lot of repowers using the volvo D series with duoprop drives. There hasn't been one where the cruise speed has not increased by at least 10 mph, but the gains are not as impressive if at all on the top end. In theory if the hull design is effiecent enough and there's enough torque available why not grab another gear. Also in terms of power needed, if you could harness the torque properly you wouldn't need an 800hp diesel to replace your gas motor. I swapped two 525sc for 310hp inlines and picked up 16mph at cruise at about 12gph combined...
Now go easy on me, just throwin my 2cents in the mix

stainless

So what if we had a 550 hp engine with 1100 ft lbs of torque and a 2 speed tranny would that break 110 in a 36' cat ?

HabanaJoe

I'm going to brow beat you watch out!!!!

Your 525's swap out what happened to top speed?

I agree with everything you've said.

I would ask you are the speeds at which you want to run in the 50-60's? That seems to be the barrier, above those speeds you need the Hp and overdrive gears to get it done.