engines comparing

[Lee Jerry]

You also need to provide a little more information. In particular, are you planning on using the same (existing) transmission(s)? are you planning on using the same (current) propeller(s)?

Are you planning on DIYing this yourself or have it done professionally?

And then there are issues of engine bed alignment, plumbing, etc., which can affect how difficult the change is.

[Aravind]

I am not planning on using the same transmission or propellors. I will not DIY the engine installation.
The engine room has been cleaned out for complete re-epoxy and install. So I can basically pick and choose, that is if it fits within budget and expectations.

[ranger58sb]

Originally Posted by Aravind

I am aiming at an engine that does 700+ torque, 200bhp.

Am I correct in comparing the engines this way?
I thought the 6cyl would be more efficient, but looking at the data the 8LV looks like a good choice?

Originally Posted by Aravind

the current engines have to be rebuilt completely.
maybe it is better to invest this money in to something more economical, rather then in the old stuff? A rebuilt probably costs over 5k US.

Once you get all your comparative data on the same page... looks like an OK way to start. But then you'll also want to take dimensions into account.

I think I'd also add the Cummins QSB (either version, if they still make the 5.9L too), and Cat... and since you're in Europe, also comparable engines from MAN and Volvo.

An inline 6 could give you significant improvement in free engine room space, compared to a V8.

Assume you'll need new gears, new mounts, possibly new shafts and props, etc.

And then compare new costs against projected costs to rebuild your 3208s and re-hab existing gears if necessary.

-Chris

[newhaul]

Have you looked at the French built Perkins M250C specs look good to me .
Looks to be about 15 to 16 lph at 200hp
https://www.frenchmarine.com/product...e-250hp-1435-1

[Lee Jerry]

Originally Posted by Statistical

The fuel consumption numbers are based on the propeller curve not the peak output curve.

For the Steyer at 2,400 rpm it is consuming ~18l/h but that is based on the hypothetical prop curve above which is ~72 kW or 95 Hp. To produce 200 HP (~150 kW) would be 3,300 rpm and consume ~40 l/hr.

Likewise the yanny does 200 HP at around 3,100 rpm which also is ~40l/hr.

If you are cruising globally hard to beat yanmar part availability. That would be a factor for me.

Originally Posted by Aravind

ok I see what you mean. I need to use the prop hp instead of the crankshaft hp.
wish I could edit the first post and correct it :d

Statistical has you on the right track - the nominal prop curve determines the operating point. (Note this is only a nominal curve; the "actual" curve will depend on the transmission and propeller characteristics as well as the hull drag characteristics, and then will vary with the wind and sea state. We can get into it more if necessary, but at this stage the nominal curve is good enough.)

I get slightly different numbers for your three engines:
Steyr gives 200 hp @ 3300 rpm consuming ~43 l/hr.
6-cyl Yanmar gives 200 hp @ 3300 rpm consuming ~41 l/hr.
8-cyl Yanmar gives 200 hp @ 3000 rpm consuming ~36 l/hr.

Note, however, that the 8-cyl Yanmar is a bigger engine than the other two, producing more power and torque, and with a larger footprint - roughly same length as 6-cyl but ~1/3 wider. You said this was important.

Also note that the Steyr doesn't produce as much torque as either Yanmar and also reaches max torque early and then tapers off somewhat more quickly. This might be an issue with prop match, meaning less thrust (speed) at given engine speed. (Or maybe not, need more analysis.)

Of these three, the 6-cyl Yanmar looks like the best option on initial look.

[rslifkin]

Originally Posted by Lee Jerry

Note, however, that the 8-cyl Yanmar is a bigger engine than the other two, producing more power and torque, and with a larger footprint - roughly same length as 6-cyl but ~1/3 wider. You said this was important.

The 3208s coming out are physically rather large engines for their power output, so even though the 8LV is still a V8, it's almost certainly smaller in every dimension than the 3208s.

[Lee Jerry]

Originally Posted by rslifkin

The 3208s coming out are physically rather large engines for their power output, so even though the 8LV is still a V8, it's almost certainly smaller in every dimension than the 3208s.

OK, that may be. I didn't look up the old, was only comparing the new options.

[skipperpete]

Why not get Cat “Reman” 3208’s and stay with what you know best. All the other engines on your list are common rail and some have at least a few fragility’s ( other than the common rail system) that can ruin your day. I had a few problems with Steyr engines and avoid them as much as possible, I’ve never even seen the Yanmar V8 but really like the 6LPA, I worked on an single installation of one of these in an 84foot sailboat and it still performs flawlessly.
Do you use the yacht for crossing oceans and do you rely on your main engines completely? For some of those engines on your list there are no reliable parts and tech support although since Thales bought Steyr from the Chinese that may have changed ....but which ever engine you choose, I suggest you carry a complete set of sensors although with the twin installation you’ll always be able to make progress if one engine fails.

[Aravind]

I acquired some new data, and it seems like 100hp @ prop is plenty.

I have been absorbing all of your info, and also found some new data about my current engines:
Cat 3208 data
According to this brochure, the current twin engines each (210hp, 722kg, 1592lb, bottom one in the folder), each do:

---- @ engine -------------------------------- / (+- @prop, read from graph)
2800rpm - 157bkw - 534Nm - 210bhp / 157kw - 210hp
2600rpm - 125bkw - 460Nm - 160bhp / 130kw - 160hp
2400rpm - 99lbkw - 392Nm - 125bhp / 95w - 130hp
2200rpm - 76bwk - 330Nm - 100bhp / 70kw - 100hp
2000rpm - 57bkw - 272Nm - 78bhp / 60kw - 78hp
1800rpm - 42bwk - 221Nm - 58bhp / 40kw - 62hp
1700rpm - 35bkw - 197Nm - 50bhp / 30kw - 50hp
1600rpm - 29bkw - 174Nm - 42bhp / 25kw - 40hp
1500rpm - 24bwk - 153Nm - 37bhp / 10kw - 35hp

The ship was able to cruise @ 2200rpm, 100hp net, 330Nm Torque, 10knots, using 2x 20Liters of Diesel.
The ship is a steel sailboat of 79 feet, weighing 75tonnes.

I'm still considering which engines to replace these fat 3208's with.
My priorities are:
1 - fuel economy
2 - easy maintenance, mechanical preferred over electrical
3 - engine size (I prefer smaller)
4 - cost price (bigger engines cost more)

Since the engines to be installed are auxiiairy engines (it's a sailyacht after all), would twin 4cylinders be good enough? Most boats of this size/weight have a solo 6cyl. so why would I put twin 6cyl in?
I will cross oceans, but sail 80%+ of the time. On top of that, there will be a 10kw+ parallel hybrid added, for when there is sun and no wind, and for maneuvering in harbors etc.(5+kw of solar panels and a small 3cyl generator to feed it if necessary, still way more economical then starting one of the big engines.

- Yanmar 4LHA-STP - 240bhp - 19l/h @ 100hp MECHANICAL
- Yanmar 4LV250 250bhp 20l/h @ 100hp
- Yanmar 6LPA-stp2 315bhp - 24l/h @ 100hp MECHANICAL
- Yanmar 8LV320 320bhp - 18l/h @ 100hp
- Yanmar 8LV350 350bhp - 17l/h @ 100hp
- Yanmar 8LV370 370bhp - 17l.5/h @ 100hp
- Yanmar 6LY2M-WTD 352bhp - 20l/h @ 100hp MECHANICAL
- Yanmar 6LY2A-UTP - 370bhp - 20l/h MECHANICAL
-
Nanni: French brand with toyota blocks:
-Z4.230, 230bhp - 20l/h
All the nanni engines seem to be using 20l/h at 100hp, whether it is a 4cyl 230 or a 6cyl 300

- Steyr SE266S36 258hp 6cyl - 18l/h @ 100hp

- Perkins M250C 250hp - 20l/h @ 100hp

- Cummins QSB 6.7 250bhp 658kg, heaviest engine, can't find the fuel consumption chart.


So far the Yanmar 8LV350 looks to hit the sweet spot with 17L/h


looking forward to your replies.

[Aravind]

- Volvo D4 320hp - 20l/h @ 100hp, 2300rpm

I should have added the rpm's to all of the engines @ 100hp... that's a factor as well:




- Yanmar 4LHA-STP - 240bhp - 19l/h @ 100hp MECHANICAL 2550rpm
- Yanmar 4LV250 250bhp 20l/h @ 100hp 2700rpm
- Yanmar 6LPA-stp2 315bhp - 24l/h @ 100hp MECHANICAL 2650rpm
- Yanmar 8LV320 320bhp - 18l/h @ 100hp 2450rpm
- Yanmar 8LV350 350bhp - 17l/h @ 100hp 2300rpm
- Yanmar 8LV370 370bhp - 17l.5/h @ 100hp - 2300rpm
- Yanmar 6LY2M-WTD 352bhp - 20l/h @ 100hp MECHANICAL 2150 rpm
- Yanmar 6LY2A-UTP - 370bhp - 20l/h MECHANICAL 2150rpm
-
Nanni: French brand with toyota blocks:
-Z4.230, 230bhp - 20l/h 2650rpm


- Steyr SE266S36 258hp 6cyl - 18l/h @ 100hp 2470rpm
- Perkins M250C 250hp - 20l/h @ 100hp 1750rpm

[Aravind]

after exploring some more, I found an engine that is possibly perfect:

I'm not the biggest volvo fan, with their expensive parts and 'special' air filter replacement (including the sound silencing cap),... but this one has decent stats!
edit: perhaps the torque goes down too fast?


- Volvo D5A TA - 4cyl - 100hp @ 2000rpm - 18l/h

D5A TA product page
D5A TA specifications download link

[Aravind]

all the engines I've been comparing, and then some more...

They all are at 19-20L / 100hp

Some achieve it at lower rpm, others at higher.

I start wondering if the Yanmar 8LV stats are ... just a faulty graph.

There is something like, how much power you can extract from 1L of diesel right?

[SY Harmony]

Originally Posted by Aravind

after exploring some more, I found an engine that is possibly perfect:

I'm not the biggest volvo fan, with their expensive parts and 'special' air filter replacement (including the sound silencing cap),... but this one has decent stats!
edit: perhaps the torque goes down too fast?


- Volvo D5A TA - 4cyl - 100hp @ 2000rpm - 18l/h

D5A TA product page
D5A TA specifications download link

That’s a marinized Deutz.

[Lee Jerry]

Originally Posted by Aravind

all the engines I've been comparing, and then some more...

They all are at 19-20L / 100hp

Some achieve it at lower rpm, others at higher.

I start wondering if the Yanmar 8LV stats are ... just a faulty graph.

There is something like, how much power you can extract from 1L of diesel right?

I'm not surprised that at this early stage of design that all of the engines look about the same in terms of fuel consumption. You really need to start looking at the engine / transmission / propeller combination as a complete system to get any more refined info. You may still not find significant differences - the efficiency of the diesel process is limited and they all generally approach that limit these days.

Therefore you will need to base your decision on other requirements, such as some you've mentioned. These could include: reliability (real or perceived), parts availability, size, cost, etc.

It looks like most of the engine options you're looking at are significantly more powerful than the old one being replaced, which was 210 hp. The new ones range from 240 hp to 370 hp. Why the increase? Was the boat under-powered before? Do you have the room to turn a prop large enough to absorb this power? Also, diesels generally like to be run under load; I'm not sure they would be happy operating most of the time at <30% of rating (i.e only 100 hp).

The number of cylinders is not too critical (meaning a 4-cyl could work), other than they generally produce a bit less torque for corresponding power. Again, as long as the engine is matched to the prop, then no problem. A better metric might be the engine displacement. Be sure to check performance under a single engine, too.

Therefore, I think you are looking toward the smaller engines (in power) in your list - the 4-cyl Yanmars, Nanni, Perkins, and the Volvo D4-300 (not 320), pending the answer to the under-powered question. Note, however, that the Nanni engine sheet shows it coupled to stern drives, so make sure it is compatible with a displacement hull.

Originally Posted by Aravind

after exploring some more, I found an engine that is possibly perfect:

I'm not the biggest volvo fan, with their expensive parts and 'special' air filter replacement (including the sound silencing cap),... but this one has decent stats!
edit: perhaps the torque goes down too fast?


- Volvo D5A TA - 4cyl - 100hp @ 2000rpm - 18l/h

D5A TA product page
D5A TA specifications download link

I think this one is a little too small at only 160 hp. (The torque might not be as bad as it looks, though, because it is shown on a compressed scale making it look like a steeper drop off.)

[skipperpete]

It hurts to say this but the Volvo D5 doesn’t seem like a bad choice, individual injector pumps instead of common rail is a big plus and I like what appears to be some sort of manual oil change pump built in.
For a bit of clarity, one sailing yacht that I’ve worked on in the same length group (75’-100’) had 2 Cat 3208’s and Hundested propellers and really needed that amount of horsepower. A Swan 80 had twin D-3110’s and was over powered ( that bugger could really sail) and a 100’ European built yacht had a singly chunky V8 MTU but also a handy boat under sail. I replaced a turbo on a 75’ sailboat that had a single Yanmar 4LHA-STP, good sailer but underpowered with that engine. Finally an older design Swan 84 with a single Yanmar 6LPA- STP, a good fit for this particular design.
Is your yacht a good sailing vessel or does she fall into the motor sailer category? This has a lot of impact on getting the appropriate power plant to suit both your pattern of usage and vessel type. Oh, before I forget, I repowered a Swan 65 with a single Yanmar 4JH series 125 hp engine and the size of the prop it could swing was too small , she’d run up to 9 knots cruising and maintain that speed but was a real pain to stop or maneuver coming in to berth..... like dangerous!
Hope this info helps.