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Old 12-30-2010, 06:50 AM   #21
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Cummins....

Quote:
FF wrote:

rpm with a 6BT 220 HP.

This is probably the truck rating.

If you find the 24/7 rating it may well be half of that , so 45 hp is not all that bad.

The key for a trawler is NOT to have a turbo, that may require some minimum RPM in order to survive.
The original 6BT motor was 210HP. Continuous duty rating was 15% less.* This was for marine applications long before Dodge started putting them in trucks. They also made a 6B natural at I think 150 HP. Over the years they just kept cranking the out put up and adding after coolers etc. You can get 370 HP out of a 6BTA. This is like the DD 6-71 story. My Grey Marine (original 6-71) was 165 HP. When they were done with it, the JT turbo 4 valve head was over 400 HP I believe.

Anyway, the 6BT 210 HP was the original bullet proof engine that ended up in so many 28 to 40' commercial crabbing boats on Chesapeake Bay.

Ted

*


-- Edited by O C Diver on Thursday 30th of December 2010 08:01:37 AM
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Old 12-30-2010, 07:33 AM   #22
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Cummins....

Ted, the 671s for normal sale got up to 485 hp - I made an offer on a*150 hour (Tolly 48)*that had them. They were part of the last production run and had been crated for several years before replacing the original 6-71s on this sinker boat. GM had just started building the Series 60 diesel*which saved their bacon, at least until Roger Penske came along and bought out DDA.

The engines ran great and did not leak. GM had finally figured out how to minimize 2 cycle drool and was using good gasketing material towards the end of the 6-71 run.
But I shuddered to think what the engine longevity at this rating would be when run at 80 to 90% rated RPM.

I also made an offer on the same identical vessel with 700 hour 300 HP 6BTs. It was a very different 'feeling' vessel with* much lighter, more fuel efficient*and quieter engines. With the Cummins,*The Tolly*ran on plane beautifully at 2200 RPM, well down the power curve.


-- Edited by sunchaser on Thursday 30th of December 2010 08:36:19 AM
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Old 12-30-2010, 09:34 AM   #23
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RE: Cummins....

"This was for marine applications long before Dodge started putting them in trucks. They also made a 6B natural at I think 150 HP"

Dodge put them in trucks in 1988 at 160 hp @2500 rpm. *I believe they were in boats in 1986.
The natural was 130 I believe.

It is hot exhaust that gets the turbocharger spinning. Run the engine easy = low EGT = low rpm on the turbo and not much, if any boost.
In both my truck and marine 6BTs I started to see some boost at about 1600 rpm under "normal" conditions.
*
The condition that a turbocharged marine diesel does NOT like is IF it is RAW water aftercooled with little or no boost the intake air is very cold esp in northern waters. That makes the intake air charge cold and can fill the aftercooler with moisture/oily yuck mix (if you have the PCV vent going back into the turbo). That also makes the combustion chamber cold and can carbon*things*up.

The 6BT 210/220 has NO aftercooler so this problem*does not *happen. Also the 250/270 hp versions are "jacket water" (antifreeze) cooled and they also do not have this problem.
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Old 12-30-2010, 09:53 AM   #24
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RE: Cummins....

Quote:
jleonard wrote:

..... They also made a 6B natural at I think 150 HP"....



.....
The natural was 130 I believe.....

It is hot exhaust that gets the turbocharger spinning. Run the engine easy = low EGT = low rpm on the turbo and not much, if any boost.
In both my truck and marine 6BTs I started to see some boost at about 1600 rpm under "normal" conditions.



I was going to interject the same thing about turbos but you beat me to it.

*

And the natural 6b was 115hp....and they are very rare!!! *I have seen ONE! *I would imagine them to be excellent engines though.
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Old 12-31-2010, 05:05 AM   #25
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RE: Cummins....

Modern thinking is a block can burn just so much fuel .

So at 70% power on a 115 hp engine the engine might burn 4gph.

Boost the power to 440hp at 24 gph fuel burn the engine will last 1/6 as long , in hours , but will have burned the same amount of fuel.

The key concept is the 440hp version is built very different from the starting 115hp version,

and simply running the 440hp at 4 gph will NOT get the service life of the 115.

This is where the under loading concept/problems comes from and what make the concept "fast trawler" an OXYMORON.
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Old 12-31-2010, 11:15 AM   #26
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Cummins....

As noted by many posters, the 6BT and its variants is a long time common use engine. The 300 and 330 hp Cummins made during the past 20 years are regarded by many as the penultimate diesel for "light" marine, work vehicle*and fixed base use. The weak links for marine use are the hang ons such as the water pump and crank shaft belt idler/pulley. This basic setup powers thousands of gensets sold and manufactured around the world. Add to that the tens of thousands of Dodge pickups and carryall vans, the engine should be consideredproven. It has far surpassed the commonality of the ubiquitous GM 6-71*

-- Edited by sunchaser on Friday 31st of December 2010 12:28:47 PM
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Old 12-31-2010, 11:33 AM   #27
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RE: Cummins....

Quote:
sunchaser wrote:The 300 and 330 hp Cummins made during the past 20 years are regarded by many as the penultimate diesel for "light" marine, work vehicle*and fixed base use. The weak links for marine use are the hang ons such as the water pump and crank shaft belt idler/pulley.
Could not agree more.

*
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Old 12-31-2010, 11:37 AM   #28
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RE: Cummins....

I just had a new coolant water pump installed and I am on my second Sherwood raw water pump. I wonder how much a idler/pulley costs and if it is DYI?
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Old 12-31-2010, 11:46 AM   #29
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RE: Cummins....

The idler pulley is a cake job as long as you can get to the front of the enigne.
Not sure what the assembly costs. I know there are upgrade kits the truck guys buy that are supposed to be superior to the OEM assemblies.
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Old 12-31-2010, 12:23 PM   #30
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RE: Cummins....

Doc - As Jay and other Cummins guys who follow boatdiesle know, the Sherwood pump can be replaced by the Seamax unit from Seaboard.
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Old 12-31-2010, 12:54 PM   #31
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RE: Cummins....

Will a truck pulley fit a boat?
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Old 12-31-2010, 01:59 PM   #32
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RE: Cummins....

"Will a truck pulley fit a boat?"

I would say yes but I am not 100% positive.* I have a truck engine in my garage the the tensioner pulley measures roughly 3 inches OD if that helps.
I also have a marine engine but the pulley is missing so I can't compare.
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Old 01-01-2011, 09:56 AM   #33
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RE: Cummins....

There is an upgrade to the bolt for the idler pulley that can be done with some time & effort.
Courtesy Seaboard Marine, Tony Athens.

http://sbmar.com/main/articles/idler..._6bt_6bta_5.9/
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Old 01-01-2011, 06:27 PM   #34
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RE: Cummins....

Ah Ha! I Had no idea that there were two issues...a tensioner pulley and an idler pulley. Whio knew? I thought tha the tensioner was the weak link but it looks like the other one is guilty.
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Old 01-05-2011, 07:28 AM   #35
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RE: Cummins....

Can anyone answer this? Neither of mine need fixing now, that I know of, but that has not stopped me in the past.
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Old 01-05-2011, 11:34 AM   #36
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RE: Cummins....

As with my Sherwood SW pumps, I seem to be getting reasonable longevity from the serpentine belt tensioner.* The first one went 1750 hours before it started making a little bearing noise.* It's replacement is still on the engine after 3200 hours and seems to be doing fine.
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