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Cummins 4BTA mods

Old 04-19-2019, 08:51 PM
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Default Cummins 4BTA mods

Anyone familiar with these engines knows about the poorly designed and poorly placed seawater pump. After years of dealing with it and pulling my hair out getting the port side pump out I decided to do something about it. I designed a bracket off of the front inboard motor mount of each engine and mounted a pedestal style pump driven by a cog belt. I have enough room in front of the engines to do this after moving the Racors. This will work on any B series Cummins. At the same time I had to replace both after coolers. After almost 20 years I guess it had to happen. They are NLA, so I had to retro fit with a pair of Bowman coolers. Had to get clever with the air tubing etc. I am going to sell the Sherwood G1503 pumps, only have 120 hours on them since installed in 2014 and no leaks. Impellers are removed.
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Old 04-19-2019, 08:51 PM
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I can't post pics of the project here until I have 10 posts.
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Old 04-20-2019, 04:14 AM
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I would be interested in seeing your mods. I have 4bta's and a water pump failure wiped one of them out about 5 years ago. Since, I have been doing a major rebuild on my pumps every other season. Last year, I took the starboard pump out for it's semi-annual rebuild and the seal was already leaking grease. It was only a short amount of time until the pump was going to fail. Go out and reply to a few threads until your post count reaches 10,
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Old 04-20-2019, 09:29 AM
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Ok, will do that.
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Old 04-20-2019, 09:30 AM
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BTW, what boat do you have them in?
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Old 04-20-2019, 09:55 AM
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Take a look at this website. He has his own forum where he answers questions about cummins engines. He also has a Tony's tips section where there is a lot of information about cummins diesels. He also makes his own seawater pump for cummins. He's easy to deal with any has helped a lot of people over the years.

https://www.sbmar.com
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Old 04-20-2019, 08:56 PM
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I have been on the SBMAR site and purchased items from him. Just got 8 new of his engine mounts from him.
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Old 04-21-2019, 06:12 AM
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I have 4bta's in a Carolina Classic 28. I and others have done extensive research regarding these raw water pumps. SBMAR does not make an updated pump for the 4bta engines. They do make them for the 6bta. Tony Athens did not see enough sales volume for the 4 cylinder Cummins engines to spend the time and money to engineer a replacement pump. Also, you can only get this particular Sherwood pump from Cummins. The last time I bought a new one, it was North of $1100. I get my pumps rebuilt at Depco Pump in Clearwater FL. They do an excellent job at a fair price, typically at one third the cost of new. My 4bta's are great engines. They run reliably and have taken me offshore and back safely many times.

Once while speaking to a tech at Depco, I asked him why these raw water pumps were so terrible. He told me that the bearings in this raw water pump were too small for the large amount of overhanging weight. That big gear just weighs too much for the relatively small bearing set supporting the pump shaft.
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Old 04-21-2019, 07:50 AM
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I had emailed with Tony about different pumps, nothing he has fits in that spot, as you said. I looked into many different alternatives to the sherwood pump and also spoke with Depco. If you look for 4B performance parts online you come across many businesses that cater to the cummins in a jeep swap crowd. They make all sorts of billet items including gear case covers. I was all set to have a cover made that would mount the r/w pump in front of the engine, just opposite of the current spot. But it did not really change access to the port side pump all that much, Plus any other pump was pumping way too much water so I went with a crank driven pump driven at a 1 to 1.3 ratio. It will pump just a hair more if I figured this right. I will post pics once I have the ten posts, only allowed 5 a day so far. How much room do you have in front of your engines?
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Old 04-21-2019, 08:49 AM
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I have plenty of room in front of my engines. An average guy can get in front of the engines and have room to move around. Changing the pumps is not really a problem. When changing the port side pump, a small jack and a wood wedge are needed to support the engine when the motor mount is removed. Changing the starboard pump is easier, since no jack is needed to support the engine. I am interested in how you setup the crank driven pump. What boat do you have your 4bta's installed?
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Old 04-21-2019, 09:40 AM
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I have a Pursuit 3000 Express. Tightly packed engine room. The pump has a cogged pulley on it, and I had a crankshaft adapter, like a dry sump oil drive, turned down and put a cog on that. I made a bracket to mount the pump on. I will post pics when allowed.
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Old 04-21-2019, 10:58 AM
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BTW Fine Catch, do you still have the Cummins after coolers? Mine took a hit this year and I just got done setting up Bowman coolers.
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Old 04-22-2019, 03:27 AM
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finally able to add pics



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Old 04-22-2019, 05:00 AM
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I still have the original Cummins aftercoolers. I had to replace one when I had the starboard engine rebuilt 5 years ago. Cummins was not able to provide a new one, but did find a used one at that time. Did you do that mod to both engines? It does not look like something that you can do with the engine in the boat. I assume that you can not use the stock pulley guard anymore. Have you actually run the boat with your new raw water pump setup yet?
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Old 04-22-2019, 06:19 AM
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I had the pulley guard taken off years ago, there was no way I could change the belt if needed. The engines are not in the boat now, and I don't believe I could have done this job with them in. I had to make all the brackets so I needed to be able to get at the engine for measurements. I needed longer bolts for a few things and had to grind out or elongate holes in some brackets. I hope to test run the engines this week on the shop floor.
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Old 04-22-2019, 06:33 AM
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Best of luck with your new pump setup! The lousy raw water pump design gives an otherwise stalwart engine a black eye. For now, I am just going to be hypervigilant and rebuild a pump every year, with a major kit. Keep us posted.
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Old 04-22-2019, 11:12 AM
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I also love this engines. Fuel economy is out of this world. I average a total burn of 7 gal. per hour for the season cruising between 22 and 24 kts. I will keep you posted. When all set I am going to put those pumps on the classified board.
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Old 04-22-2019, 01:29 PM
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Originally Posted by boatmanmark View Post
finally able to add pics



I like that set up. That will work.
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Old 04-22-2019, 01:36 PM
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Thanks. Dry sump oil systems are driven like that all the time. Many diesels have belt driven pumps, that pump is from a 3208 Cat with a half thickness cam, only difference is that on the CAT it is pulley driven, a 9 inch pulley on the pump!. I wanted to keep both pumps (port and stbd engine) inboard and inside the stringers so a cog was called for. Just had to reduce the pump RPMs so as not to flow to much water. About the same flow at idle, a hair more at WOT. With half thickness cam the impeller should last a long time too.
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Old 05-08-2019, 06:05 PM
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Started up the engines today on the shop floor. The new raw water pump worked great in the new location, no vibration to the bracket at all. I have new SBMAR motor mounts on and you can see those 4BTAs really dance when trying to get fuel prime. Tried to upload the videos but I can't.
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