hull extension in progress with pics

[Tacklewasher]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

Thoughts on a diesel.

A lot of added weight vs a BB. Maybe as much as 50% more weight.

The one in the link is based on the 6.5L. Not the best auto diesel out there by any stretch. You'd be good to price a 6.6l Duramax or something newer.

Diesel is almost 25% more right now in town. Trust me, I've been watching it. Cheapest right now is $1.10 vs $0.874 (Crappy Tire). It's been a while since diesel has been cheaper than gas (close to a year).

Water in diesel is a killer. More so than in gas. Both in the fuel and coming back in the exhaust.

Harder to find a good wrench for the diesel. Not impossible, but I don't think I've seen one diesel pleasure boat on the lake.

Won't be able to fill up on the lake.

Much more difficult to quiet a diesel.

Love to see it done as I love diesels, but I'm thinking it's a lot more headache.

 

[Larcus]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

Oops, I think a diesel would be the thing if it was not too heavy. Maybe like this one. Man it sounds GOOD.
http://www.youtube.com/watch?v=LkWnbS0Qfrg

 

[erikgreen]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

A marine diesel is basically a diesel with non corroding parts and seals, and a cooling system that has a heat exchanger for lake/ocean water, plus provision for a wet exhaust.

Mercruiser once upon a time had a line of I/O diesels (D-tronic) but to put this (above) engine in a boat you'd need to have most of the add-ons custom built.

On a related subject, I ran across a place that would convert a Duramax diesel for marine use at a total cost of about $12k per engine.. I can look that up if you want.

But yeah, with all the add-ons for marine use it'd be more than 50% heavier than a big block, possibly up to twice as much.

For this size boat it might make sense to use a small diesel engine, like an automotive 3.X liter one, but a big block diesel is probably more than you have space and weight for. Heck, a big block chevy is probably borderline, unless you use stainless manifolds and aluminum heads to shave some lbs.

Diesel fuel is more expensive, but it's a wash when you compare how much more energy you get out of a gallon of fuel vs. gasoline, IE you go farther on the gallon of diesel than gas.

Erik

 

[NoKlu]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

Diesels do produce a lot of torque but at what rpm? Newer truck diesels torque drops after 1500 rpm. Go higher and you just burn a lot of fuel and the torque drops off quickly. They need to run at the top of the torque curve so I'd want to see the Dyno chart before I would even consider one.

 

[Tacklewasher]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

For this size boat it might make sense to use a small diesel engine, like an automotive 3.X liter one, but a big block diesel is probably more than you have space and weight for. Heck, a big block chevy is probably borderline, unless you use stainless manifolds and aluminum heads to shave some lbs.

Simple solution to that is he makes the boat bigger (again)

 

[Renny_D]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

Outside of the weight a duramax would be an awesome engine - they can do an easy 800 ft/lbs torque on a fairly mild tune. It would need larger injectors, larger turbo, air/water intercooler and a chip but you'd make that kinda torque all day long. A Duramax is a fairly high reving diesel especially for it's size and is lighter and much more powerful than the 6.2 liter na or the 6.5 liter gm turbos which were the predessors of the duramax. Still a turbo or supercharged gas engine would be more fun and the turbo would get the better fuel economy of the two.

Thanks

 

[NoKlu]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

I did some looking and GM says the duramax produces max torque at 1800 rpm. Just under 600 ft lbs, from 1800 to 3000 it drops steadily to 550 ft lbs. After 3000 it drops like a rock,straight down.

 

[erikgreen]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

Noklu, when does it drop below 300 ft/lbs?

Remember, for marine use we don't need huge amounts of torque all across the RPM range, we just need minimum torque at any given RPM to spin the prop we choose up to optimal RPM for that prop.

If you look at the dyno of a stock big block chevy engine, which most of us would agree works well in a boat, then you'll see that max torque is also achieved at 3000rpm, and it drops after that. The difference is that a diesel gets max torque faster.

As long as the Duramax gets the minimum needed torque for the prop Oops uses at all RPM ranges, it'll work nicely even with a 1:1 gear ratio. Especially if he operates it at just above planing speed a lot (most fuel efficient speed).

Here's a great link on the comparison between gas and diesel engines in boats. This guy has some interesting opinions in there, but in general he presents a lot of good facts and explanations. I recommend you guys check it out:

http://www.yachtsurvey.com/GasNdiesel.htm

Erik

 

[proshadetree]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

How about a b20 Honda engine with a turbo 15psi boost and twist it to 8000 rpm.It'll live a long time Ive seen several stock units boosted with over 200thousand miles on them live for several years.Sort of joking Cant wait to hear what ends up i the bay.I like many others do prefer a big block lightened up with a head and intake swap.But compared to the old 4.3 you had a mild 383 would still be a great choice.Diesel plants are heavy and off hand I couldnt tell you how to get one lighter,Not a lot of market for that yet.

 

[NoKlu]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

With a Diesel engine it's not the optimal speed of the prop you should be concerned with. The optimal speed of the engine is what you need to be concerned with. Run them too slow and they burn up. Run them to fast and the efficiency and longevity go out the window. The operating range of a diesel is about 300 rpm despite what they are trying to do in the pickup trucks these days. Just ask any of the diesel truck owners how much work they have to do to there motors. The only way I can see a Diesel working in a boat and getting a long life is with a CVT transmission so the prop and the engine are both working at there optimum rpm and staying at that rpm. The duramax engine seems like a good engine but they don't last. GM put lousy injectors in them and they almost all have to be replaced. Some get lucky and get them done before they blow the engine but a lot do not. I am in the market for a new truck right now and got offered an 04 Duramax with a brand new $17,000 engine in it with only 170,000 km's on it. My boss want's me to buy his 03 with only 130,000 on it. His warranty work was only $12,000. 2 guy's I work with have dodges with the cummins and both have all new injectors and one a new engine and both are less that 3 years old. If I get a diesel truck I get all of my fuel free but unless the truck is almost free I will buy a gas powered truck. In the proper environment a good Diesel will run for a very long time.My experience with diesel does not come from reading it comes from 30 years working with them.

 

[oops!]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

12 valve cummins.....mines got 320 k youve pulled in that truck havent you?

 

[oops!]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

awesome stuff bubba.....as usual......i could not be happier with all the info that is coming out on this thread



alll you guys deserve a big pat on the back !

 

[oops!]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

Hang on a second folks, lots of information here that seems to go a bit astray. When talking about engines, torgue and HP there seems to be some confusion so let me try to clear it up. First, there is no such thing as horse power other than as a mathmatical abstract, it doesn't really exist. Horse power is nothing more than a formula that uses a turning shafts RPM and Torque to come up with a horse power number. Thats all it is, just a number, it has little meaning when we are talking boats with one exception. Horse power is a very good way to measure actual work done. By using a horse power number we can compare very different types of work done. As an example, a steam boiler has a hourse power rating, a jet engine has a horse power rating even though we measure its thrust. Its a handy way to be able to compare apples and organges.


I put together the following chart to demonstrate this and anyone wishing to copy it for another day feel free. Across the top is the Torque in pound feet, on the left the RPM, and in the center the calculated horse power.
Example, a shaft spinning at 2500 RPM and delivering 250 lbft of Torque is preducing 119 horse power.

In a boating application, Torque is everything because the prop requires a specific amount of torque to spin it at a given RPM. (Assuming its in the water) In fact, because of the nature of a boat, the prop is using 100% of the torque delivered to it 100% of the time. That is a very important distiction over almost any other engine use like a car.

If you want to increase the speed of the boat you increase the RPM of the prop, and that requires an increase in torgue. There is no such thing as getting on plane and coasting, unless you reduce throttle.

Some might think the best thing to do is keep an engine at its maximum torgue RPM. Lets say a 454 chevy where the peak torgue is around 3000 RPMs. Sorry but no, and this is where the horse power number comes in. Remember I said horse power is a handy way to measure work done? Ok, in the case of our prop work done is the amount of water it displaced in a given amount of time. The more water it displaces in a second, the more work it is doing. (Or conversely how far it moved the boat in the water. For every action there is an equal and opposite reaction. )

Look at the chart and lets assume our 454 has a peak Torgue of 300 lbft at 3000 RPM. It is producing 171 horse power. Now lets take the RPM up to 4750 and we know the torgue curve falls to say 250 lbft. A quick check of the chart tells us at that RPM its producing 226 horse power and is doing that much work (displacing more water). Thats almost a 25% increase in the work done in the same amount of time. End result, you go faster. (Or pull harder.)

I've been doing a bunch of reading on prop design and I hope to put together the other half of all this, how much torque does it take to spin a given prop at a given RPM. I hope to post it in the next few days hoping it might make life easier for guys repowering boats. I would have done it sooner but Opps! stole my round tuits...

this was posted by bubba​

im just bumping this chart to the next page.

 

[erikgreen]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

Nice table. One refinement... it's not enough to measure the torque and RPM at the engine shaft, you need to measure it at the prop shaft. Mercruiser started doing that a few years back and their reported numbers changed a lot.

On the duramax vs. others, I think really diesels in small boats are a neat concept, but the newer automotive turbo diesels that aren't naturally aspirated are really too new to have good boat applications yet.

If you could find a used D-tronic (Mercruiser diesel) setup, that might be perfect. But, they're rarer than hen's teeth.

But... if Oops had the budget, these would be super neat:
http://boatdiesel.com/News/News.cfm?P=20081103_Caterpillar.cfm

Or, more realistically, this one:
http://www.sea-pro.com/mercurymarine/mercruiser/Inboards/diesel/D4point2L-D-Tronic.htm

You can get it reman from Mercruiser for I think less than $10k, and it's designed to work with a Bravo 3....

Erik

 

[NoKlu]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

The older Diesels like your 12 valve and the 6.5 were designed and built around older proven diesel designs. The new engines are just that, new designs, almost experimental, allways evolving. Just like microsoft they release a new OS then develop it while it's in the market. The big problem these days is the big 3 are on the ropes, no money so they have been cutting corners again. Last time gm was in trouble all the paint fell of thier cars cause to save money they eliminated one step in the prep before paint.Of the 22 guys on this rig there is 2 gas trucks. All the rest are new diesels and every one of them has had expensive repairs done to the engine. Some more than once.

 

[erikgreen]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

Doesn't matter which shaft you are talking about, these numbers still apply. Heck, could be the shaft of a windmill.

You're right that the basic calculations apply regardless of what's rotating (doesn't even have to be a shaft), but when comparing marine engines and calculating what prop will work you have to look at how the drive unit (B3 here) affects torque and RPM.

It's not correct to look at a boat engine producing 350 ft/lbs at 4000 RPM and say it has 267 HP at the prop. It'll be less depending on the efficiency of the drive, and torque and RPM may be really different depending on gearing.

I'm being picky here, mostly I'm posting this to remind everyone involved with this discussion that when comparing engines you should know where you're getting the numbers. I believe Mercruiser currently gets all their HP ratings for a given boat at the prop shaft.

Erik

 

[colobiker]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

I wish Merc, Volvo, etc. would tell us what RPM they are talking about when they say 250 horse at the prop. Or even better, publish a torque curve!

I agree. numbers are just that numbers.. equating to worthless information. unless you know how they are related.

I remember going to a seminar once.. a company was marketing this electric motor no bigger than your fist.. and quoted it as being a 5 hp motor.. I was like wow.. at what rpm.. .. 15000.. ... so essentially it was practically wothless for the application i was looking at..

unless the manufacturers relate the torque, horsepower and rpm (torque curves are the best).. its just a marketing number.. oh this motor produced 700hp.. (just before it threw a rod through the block)

I actually have some software that you can put in different information about a certain engine and gearing, intake parameters, exhaust parameters.. and it will spit out an approximate torque curve.. )I did a test on my buddys elcamino that had a newly rebuilt engine by a race shop..(yes they did a dyno test and gave him the torque curves)).. the curve spit out by this software and the curve given to him by the engine builder were almost identical.

this software was developed by people associated with NASCAR. as a quick way to judge if making certain adjustments to engines would be worth it, with out building an engine and running it on a dyno. I will have to see where iput that software.. might be worth digging it out for this discussion

 

[erikgreen]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

I agree. numbers are just that numbers.. equating to worthless information. unless you know how they are related.

That's exactly what I was trying to say in a more wordy way. Well done!

this software was developed by people associated with NASCAR. as a quick way to judge if making certain adjustments to engines would be worth it, with out building an engine and running it on a dyno. I will have to see where iput that software.. might be worth digging it out for this discussion

For the purposes of discussion, sure.. only problem is that the specs are probably set up for a car exhaust and drive train, so we'd have to be careful what assumptions we made.

HP is used all the time as a marketing gimmick, right up there with "Hemi"... that's why I sorta cringe when I hear car enthusiasts start talking about getting "extra ponies" in a boat

If anyone hasn't read this, I'd like to re-recommend it - it's good reading, and you'll learn a lot about marine engines, why using a maxed out engine design isn't a good thing, and some other useful stuff on gas and diesel. Really the whole site is pretty nice:

http://www.yachtsurvey.com/GasNdiesel.htm

Erik

 

[colobiker]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

erik,

excellent article. thanks for sharing... boy do I have alot to learn about
marine engines.. v.s. automotive engines.

 

[Tacklewasher]

Re: hull extension in progress with picks

Re: hull extension in progress with picks

Hey oops!.

How about mounting twin 200's on the back?

http://vancouver.en.craigslist.ca/boa/936370093.html