Continuous Rated Engines

[Ski in NC]

Yea, a 370 at 1200 in gear should be pretty social continuously. If it started loading up and smoking, sounds like it has a problem. They may be a bit smoky at dead idle, but above about 900-1000 it should be pretty clean.

Still doubting the numbers I posted a couple threads up, but they came right off the Cummins burn data charts. Might poke around with some other charts.

 

[DavidM]

Ski:

All logic and limited experience tells me that the 220 hp B would be more efficient at low speed than the 370 hp B. Why?

1. The 370 hp B may have lower compression which is going to reduce combustion efficiency until the turbo kicks in.

2. The air intake flow path for the 370 hp is going to have more restriction (air cooler) than the 220 until the turbo kicks in resulting in lower volumetric efficiency.

3. The 220's injection pump and injectors are operating closer to design flow rate than the 370, resulting in a better and more efficient spray pattern.

OTOH is there something significantly different mechanically between the two engines: 12 valves vs 24, or???

So the obvious question: is Cummins fudging the numbers? Maybe they only had real data down to 2,000 rpm and some engineer decided to extrapolate with a drafting curve downward ;-).

David

 

[Ski in NC]

Same number of valves, head is the same AFAIK. Turbo is larger, so it actually chokes flow less at lower power settings. Need to check on CR. Air cooler will have no significant delta P at low flow rate. Difference may be in the injection: 370 uses a very expensive, robust and high pressure P7100 that I think has variable injection timing. 220 uses the rather crude CAV rotary pump, not sure if that has variable timing. Getting the timing optimized at low power setting has a big effect on BSFC. If optimized for full power and no variable mechanism, that might explain it.

Your extrapolation explanation might be the most plausible...

 

[dhmeissner]

Sorry, I have nothing to contribute to this thread. Just stopping by for a beer.

 

[Donsan]

Sorry, I have nothing to contribute to this thread. Just stopping by for a beer.

Be a REAL contributor and buy us all a beer!

 

[sunchaser]

Some years ago I managed a interesting mine where no power lines were even half way close. When purchasing our gensets we requested as part of the bid guaranteed fuel burn. This was complied with by the bidders and was a major part of the decision. The spread was about 5% as best I recall and amounted to many dollars when spread over the year. The 4 units we purchased easily met the guarantee but had to be operated well up the bsfc curve to achieve the results.promised. This was twenty years ago.

Fast forward to 5 years ago where a similar request was made this time for 400 ton haul trucks operating at 15,000 feet. Dynamometer testing over the entire operating range was used to establish fuel burn and HP output which translates to cost per ton hauled. The variance between Cat, Cummins and MTU diesels was noticeable and part of the decision criteria. Boring stuff I know but important nonetheless as equipment selection for an 80,00 hour unit must be solidly based.

Today's light truck diesels will be subjected to Dyno testing to meet emissions for the entire operating range, idle to peak RPM. The Cummins 6B falls into this category so I'd guess Ski and David that no extrapolation was done, but rather real world data.

For a marine diesel to meet Tier 4 compliance it would be interesting to know the RPM range tested. For my 11 year old engines when updated dyno testing was used to establish BSFC for Tier 3 testing, absent a prop hooked up mind you.

 

[kulas44]

Put the 370 injectors in a truck and see how you like it. Turn the p pump up to 370 and you will like it even less. Turn it to 480 and its like a race car. The engine can do it just not for long. But longer than the drive train. Its a lot of fun while it lasts. Yes. the 370 has a lower cr and retarded injector timing, resulting in white smoke at low loads, which means low cylinder temps.

 

[ksanders]

Actuall use does not bear those figures out. At 1200 rpm after several hours the 370 6BTA is a nasty beast. You cant sit in the cockpit and fish. Every few hours we pulled up the lines and ran it up to speed until they cleaned up. Then good for a few more hours. High hp DDs are the same, just not meant for low speed operation.

I have Cummins 5.9L 330 HP engines in my boat. My expperience with these engines is that they love to be run easy and do not start smoking or "need to be cleaned out" like your 370's

I run my engines most of the time at 1350 or 1500 RPM. 1350 is enough to get my Balmar alternator spinning to charge the batteries and results in a speed of approx 8-8.5 knots.

1500 the engines purr and the boat makes 9-9.3 knots which is the theoretical hull speed for my boat.

I do not run at 1200 rpm because in my boat its not enough to charge the batteries or even keep up so its not a speed I choose to run.

I do run both engines at idle speed for 3-4 hours at a time trolling and never have seen any smoke or had to get after it to clean them out.

 

[kulas44]

At 330 hp they are ok. You would probably do fine with the 210 version. No aftercooler to deal with, cheaper raw water pump, etc. The 370 is on the edge for the 5.9 liter 6b. Any little thing at full bore spells disaster. The injectors are very loose and the pump is really tight. She needs a lot of boost to keep up. Lower compression and retarded timing allow for more air flow to compensate for both, which equates to more power above 2500 rpm.

 

[ksanders]

At 330 hp they are ok. You would probably do fine with the 210 version. No aftercooler to deal with, cheaper raw water pump, etc. The 370 is on the edge for the 5.9 liter 6b. Any little thing at full bore spells disaster. The injectors are very loose and the pump is really tight. She needs a lot of boost to keep up. Lower compression and retarded timing allow for more air flow to compensate for both, which equates to more power above 2500 rpm.

I asgree that the 370 HP is at the edge of what the block should produce and maintain a reasonable service life. Thats why I specifically chose the 330's when re powering over 370hp.

As a FYI the only difference between the 330 HP and the 370 HP is the injectors and injection pump. Some 330's have a injection pump that can be re-calibrated to convert to 370hp. When buying the reman engines from Cummins there was only something in the order of a thousand dollars difference in price.

The only other difference is the rpm rating of the engine.

I did consider going with the simpler engine but there are times I'm glad for the extra HP. When I want to get somewhere quickly my properly propped boat will make 14 knots at 2400 RPM with a EGT of less than 900 degrees.

 

[Steve]

See more information at this link

Cummins Engines

 

[Rustybarge]

I asgree that the 370 HP is at the edge of what the block should produce and maintain a reasonable service life. Thats why I specifically chose the 330's when re powering over 370hp.

As a FYI the only difference between the 330 HP and the 370 HP is the injectors and injection pump. Some 330's have a injection pump that can be re-calibrated to convert to 370hp. When buying the reman engines from Cummins there was only something in the order of a thousand dollars difference in price.

The only other difference is the rpm rating of the engine.

I did consider going with the simpler engine but there are times I'm glad for the extra HP. When I want to get somewhere quickly my properly propped boat will make 14 knots at 2400 RPM with a EGT of less than 900 degrees.

I would be interested in 'the ballpark' figure of your reconditioned Cummins engine in the states: here in the UK it's a special order with no published price list.


PS:brand new:
265hp v.6 3ltr cummins with bravo three drive is £29,500.($48,500)
350hp v8 4.2ltr is £43,400.(€72,900)

 

[ksanders]

I would be interested in 'the ballpark' figure of your reconditioned Cummins engine in the states: here in the UK it's a special order with no published price list.


PS:brand new:
265hp v.6 3ltr cummins with bravo three drive is £29,500.($48,500)
350hp v8 4.2ltr is £43,400.(€72,900)

In 2011...

The cummins 330 reman was $15K each sans electrical harness, starter, alternator.

or $19K each in what is called a "repower" copnfiguration which is all included drop in, connect gauge harness, etc...

My installer recommended the first option because boat manufacturers differed with their wiring harnesses, and I had a aftermrket balmar high amp alternator.

I'm still not sure which would have been cheaper. I paid to have my Balmar rebuilt, along with new rebuilt starters, new relays, new everything else. The costs added up pretty quick.

What I do know is that I like having engines that I know about every hour, and everything thats been done to them.

 

[Rustybarge]

In 2011...

The cummins 330 reman was $15K each sans electrical harness, starter, alternator.

or $19K each in what is called a "repower" copnfiguration which is all included drop in, connect gauge harness, etc...

My installer recommended the first option because boat manufacturers differed with their wiring harnesses, and I had a aftermrket balmar high amp alternator.

I'm still not sure which would have been cheaper. I paid to have my Balmar rebuilt, along with new rebuilt starters, new relays, new everything else. The costs added up pretty quick.

What I do know is that I like having engines that I know about every hour, and everything thats been done to them.

Thanks.
Wow, that's a big big saving on the new price. (Rumour has it there's a 20% discount off the 'new'list price)

Makes re-powering an old boat seem more of a viable project at those prices.

even the 'fully wired drop into place' spec is just do-able at $20k a pop....

 

[kulas44]

One of the best things about the 6bta Cummins is that you can buy an excellent condition used engine from a wrecked 3/4 or 1 ton Dodge truck for less than 3k. It will be rated at 195 to 215 hp. Even with 100,000 miles on it it is barely broke in. Have the pump recalibrated to whatever you need and put all of your marine components on it. For less than 6k you have an engine that will outlast the boat.

 

[Mule]

Or a 5.9 4 valve per cylinder rated at 250hp, I think they stopped those in 2007, EPA nonsensiby choked em out. Had to increase displacement to keep hp. Where it was.

 

[sunchaser]

One of the best things about the 6bta Cummins is that you can buy an excellent condition used engine from a wrecked 3/4 or 1 ton Dodge truck for less than 3k. It will be rated at 195 to 215 hp. Even with 100,000 miles on it it is barely broke in. Have the pump recalibrated to whatever you need and put all of your marine components on it. For less than 6k you have an engine that will outlast the boat.

The cost goes up real quick if you marinize it - things like transmission, heat exchangers, after cooler, RW pump, exhaust elbow etc. That is why the marine Cummins reman with warranty is such a deal.

 

[ksanders]

One of the best things about the 6bta Cummins is that you can buy an excellent condition used engine from a wrecked 3/4 or 1 ton Dodge truck for less than 3k. It will be rated at 195 to 215 hp. Even with 100,000 miles on it it is barely broke in. Have the pump recalibrated to whatever you need and put all of your marine components on it. For less than 6k you have an engine that will outlast the boat.

Unless you are a DIY engine builder, or proferssional mechanic this suggestion is probably actually more expensive than just buying a reman engine.

Parts add up very quickly, and so does labor. Time adds up as well, time out of the water.

I'm a very good semi DYI mechanic and I say semi because of years as a generator tech. That said when I needed a repower I outsourced it to a good full service ship yard.

They got after it, and had my boat cruise ready in short order.

On the other hand the guy two slips down from me pulled his boat for a repower last fall.

His boat is still on the hard. He has missed an entire boating season.

That is the case with so many "bargain" repower jobs. They take forever, or never get done. When they do get done the owner often has issues with them. Issues that take years to work out.

On my repower, we seatrialed the boat after the work. Then I took the boat out once on a 1/2 day cruise. Then I took off on a 1500 mile cruise to Alaska.

That was three seasons ago. Havent had any issues since. Well, I did have a starter go a bit flakey and my ship yard air cargo expressed me a new starter free of charge. The same day I called.

 

[kulas44]

What I was talking about was basically a "long block". You would still need to recondition the originall items that would be put back on. And yes, having someone else do it would make it a losing proposition. I lose sight of the fact that most folks cant do this stuff. I was using my own perspective.