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Old 10-15-2017, 05:22 PM   #1
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New to Cummins 6BT

Lifetime mechanic, but a new boat. A few Cummins 6BT questions. Where are the pencil zincs located inside the heat exchanger? Do the marine 6BT's have the same KDP "killer dowel pin" issue under the timing cover as the automotive versions? My first large boat and just starting to go through the engines.
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Old 10-15-2017, 06:20 PM   #2
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For those detailed questions, I would join boatdiesel and ask there as well as do a search for previous posts on that engine. You can also post to the sbmar.com forum which is Tony Athens' new forum mostly dedicated to the Cummins. If you post to sbmar, include your engine's CPL number.

From my memory the 6BT is a solid engine but some models have issues with coolant system plumbing, belt wrap layout, maybe the idler pulley and the raw water pump.

David
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Old 10-15-2017, 09:02 PM   #3
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Ditto David's comments. I repowered with 210 6bt's some years ago and they have been pushing us to Alaska and back faithfully ever since. Both boatdiesel.com and sbmar.com are good sources of information. Tony Athens at sbr knows everything about b an c series Cummins. I also bought the shop manuals which can be ordered from any Cummins dealer. Not cheap but a ton of information.
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Old 10-15-2017, 09:45 PM   #4
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The 6bt's I had used a single zinc in the reverse flow end, mounted in the bottom pointing up. I think it was a std 3/4" pipe plug but I did have to trim about 3/8-1/2" off the length of a std zinc or they would bottom out on the end cap center bolt.
And yes, you should check for the dowel pin, many engines made it into marine service before that fault became known.

What H.P. are your units?

Higher HP engines can benefit from a well known raw water pump upgrade, understressed units can survive without, but still good to do.
A remote mounted oil filter may ease service depending on the boats engine room layout.
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Old 10-15-2017, 10:14 PM   #5
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They 210 HP. I learned of the RWP upgrade right after buying new pumps. The Sherwoods have been working since 1989. Will consider the bypass oil filters. Have used these in other Cummins applications. Most likely a NAPA 4750 mount with 1749 bypass filter. Will order two of the KDP kits and get behind those timing covers.

Daniel
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Old 10-16-2017, 12:05 AM   #6
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++ About checking Tony Athens for KDP status. (Tony's direct approach some find abrasive, but uncontested expert). There's also some information on the idler pulley bolt & changing to a larger bolt. I did it, EZPZ. Ditto the CPL #, any 6BT advice will be predicated on that. I also had problems with the Sherwood M71 pump, still have it, but my engine is keel-cooled. I did change the mixer with a re-design that worked better with the limited flow on the pump, DeAngelo's in FtL can help with that, they've done a number of them that incorporate the design changes that I asked them to implement. My exhaust hose was running well over 250F, muffler was heat damaged. Now it's about 95-100, depending. MUCH improved.

Boatdiesel.com is a great resource as well.
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Old 10-16-2017, 05:50 AM   #7
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Shop Manual!

I wouldn’t own a boat / engine without owning the shop manual if I intended to do any of the work on it myself.

It will provide the correct info on capacities, operating temps, and the like. A wealth of info not based on hearsay.
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Old 10-22-2017, 07:34 AM   #8
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Three pencil zincs on my 330hp. Two port side one on the starboard side that needed to have 3/8” cut off of the zinc before installing.
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Old 10-22-2017, 03:40 PM   #9
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Quote:
Do the marine 6BT's have the same KDP "killer dowel pin" issue under the timing cover as the automotive versions? My first large boat and just starting to go through the engines.
I had the KDP discussion with Tony Athens several years ago when I was repowering with a 6BTA (270).
Tony does not believe the KDP is an issue as he had never seen it in his years in the marine trades.

I also had a Dodge/Cummins pickup at the time and was active in the TDR website and with a local group of dieselheads. And yes I have seen pictures of a couple of smashed up gear trains because the dowel pin came out. I have also done several KDP fixes on trucks, on both first gen (with the Bosch VE pump) and 2nd gen (with the Bosch "P" pump). I've done the drill jig method, the tab method and the staking method and believe the staking method is the best if you decide to bother.

Based on my discussions with Tony I am of the belief that it only happens in engines that are in trucks and "hopped up", as those are the only ones I have heard of that either came out or walked partially. I think it has to do with the vibrations that occur in a vehicle, that do not occur in a boat. As a mechanical engineer I have seen some funny things happen due to vibration.
I also never heard of one coming loose on a engine with a Cav pump (not sure if they were ever used in vehicles).

If it were mine I would not bother.
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Old 10-24-2017, 09:56 PM   #10
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So, the "major" parts kit for the Sherwood M71 pump does not include the oil seal? Off to the auto parts store for 5/8" id, 1 1/8" d and 1/4" wide. The complete M71 pump does not include the mounting gasket? $290 at Marinepumpdirect was the best price. The housing bolts and mounting bolts are not stainless steel, but they will be before installing onto the engine.

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Old 10-25-2017, 01:20 AM   #11
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Paul Foulston, also Boat Diesel, used to hammer on the "killer dowel pin" . He was bound and determined part, large part, of the problem was the removal of the support bracket on the cantilevered injection pump. Lots of hot rodders apparently removed those nuisances with the dowel pin result.


I have no experience but that came up often enough I remember his hammering at it.

SS bolts. Up to you but be carefull as they are substantially weaker than a Gr 5 bolt, lots weaker than a Gr8.

I'll second or third??? Seaboard Marine and Boat Diesel.
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Old 10-25-2017, 06:25 AM   #12
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How long

Quote:
Originally Posted by Pgitug View Post
Three pencil zincs on my 330hp. Two port side one on the starboard side that needed to have 3/8” cut off of the zinc before installing.
Attachment 69595Attachment 69596
Are your zincs? I have the same engines and find I don’t have to trim at any location.

Gordon
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Old 10-25-2017, 07:00 AM   #13
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Never heard of the KDP being an issue on marine B motors.

Whether you need to trim the zinc in the HX depends on where you source them. I think they are "E2" and some are longer than others. Just stick a screwdriver in the hole and sense the depth and compare it to the length of zinc and plug.

I think the B210 has only one zinc in HX, no aftercooler. Might have a zinc in gear cooler depending on where that was sourced. Factory cooler does not.

Some B330/370's have only one zinc in aftercooler, the lower plug. The upper plug generally is not submerged when shutdown so that renders the zinc useless. Most just put a blank plug up there.
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Old 10-25-2017, 09:39 AM   #14
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have an allthread connector nut on hand to remove the zincs when the brass plug comes out without the zinc.
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Old 10-25-2017, 09:51 PM   #15
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Quote:
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have an allthread connector nut on hand to remove the zincs when the brass plug comes out without the zinc.


Wow, I've never seen a zinc unthread on removal, but plenty broke off.
I install the zinc in the plug on a bench vise, clean, dry and pretty tightly.
I've always thought that was the way to insure that the zinc was making good electrical contact, thus able to function as intended.
Are you using lube on the threads?
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