Cummins 6BTA

[RT Firefly]

Greetings,
Looking at a boat with Cummins 6BTA. States 250HP. Can the HP on this engine be increased (larger injectors, more boost?) fairly readily? I fully appreciate any upping of HP will decrease lifespan but just curious. Also, does this engine have a "good" reputation?


Thanks in advance.

 

[Comodave]

I think they made ones up to 370HP. They are a great engine. Had one in our last motorhome. They put them in a multitude of Dodge trucks.

 

[O C Diver]

The 250 HP version is supposed to be very durable (from memory). Not sure which items besides injectors or injector pump change. Not sure if there is more than one after cooler model and whether it already has the larger raw water pump. Don't remember if that exhaust is the smaller or larger one. Probably need to check if the transmission and shaft will handle the additional HP.

How much more HP are you looking for?

Ted

 

[RT Firefly]

Greetings,
Zowie! Almost instantaneous response. Transmission is: ZF Gears – IRM 220V-LO.


Don't really know what upper HP limit I'm looking for but hoping to increase cruising speed from reported 17knts to somewhere closer to 20+. I have NO idea if this is feasible. Hence the question.


I expect I will have to re-prop as well. Simply a mental exercise. Thanks.

 

[Rusty Scupper]

Hi RT, I.ve been running a 6-BTA in my old pickup since 1996. Other than routine maintenance I have had zero problems. It's the old 12 valve with mechanical "P" pump.
My friend has a newer 2002 24 valve engine with electronic pump that make ungodly amounts of power. You can reach a point of no return on any engine. If not abused these
engines are very reliable.

 

[HopCar]

Rufus send your question to these guys.
https://www.sbmar.com/store/
I had a 6BT, no after cooler. It was a very solid engine.

 

[O C Diver]

Greetings,
Zowie! Almost instantaneous response. Transmission is: ZF Gears – IRM 220V-LO.


Don't really know what upper HP limit I'm looking for but hoping to increase cruising speed from reported 17knts to somewhere closer to 20+. I have NO idea if this is feasible. Hence the question.


I expect I will have to re-prop as well. Simply a mental exercise. Thanks.

You may not have to reprop as I believe higher HP comes at increased RPM.

Ted

 

[O C Diver]

My 2002 Dodge pickup has the 220 HP version. 512,000 miles, over 10,000 hours and still going strong.

Ted

 

[O C Diver]

Greetings,
Zowie! Almost instantaneous response. Transmission is: ZF Gears – IRM 220V-LO.


Don't really know what upper HP limit I'm looking for but hoping to increase cruising speed from reported 17knts to somewhere closer to 20+. I have NO idea if this is feasible. Hence the question.


I expect I will have to re-prop as well. Simply a mental exercise. Thanks.

Transmission is very close.

https://www.google.com/url?sa=t&sou...wQFnoECA8QAQ&usg=AOvVaw0uwsPYE2lvmlNYE5A_ohwU

Ted

 

[DavidM]

The Cummins 6BTA 250 hp engine is turbocharged with a coolant cooled aftercooler, not raw water as on the higher hp versions. Your question or one like it is asked once or twice each year on boatdiesel and sbmar.com's forum.

You can do anything with enough money, but at a minimum it would take a new turbocharger, injectors, after cooler and plumbing. And probably an increase in the main heat exchanger and maybe oil cooler as well. And that assumes that the oil jet cooling and other systems necessary for the higher hp are in place. Sounds like about $10,000 for parts only.

You would be better off selling the existing engine and buying a remanned 6BTA 370 to replace it with.

David

 

[Comodave]

What boat is this in?

 

[Jeff F]

I agree with DavidM. That was the highest HP motor they made with the rotary injection pump. It's impractical to ask for more from that motor.

 

[High Wire]

Greetings,
Zowie! Almost instantaneous response. Transmission is: ZF Gears – IRM 220V-LO.


Don't really know what upper HP limit I'm looking for but hoping to increase cruising speed from reported 17knts to somewhere closer to 20+. I have NO idea if this is feasible. Hence the question.


I expect I will have to re-prop as well. Simply a mental exercise. Thanks.

17 kts at what rpm? The boat may make your 20 kt target as is. Or it might barely make 17 MPH at max rpm. The sea trial will tell.
You would want to go into that with pre-defined criteria, 20 kts at xxxx rpm or it’s a no-go.

 

[Juliet 15]

We had Cummins 6BTA M3's in a Sea Ray. Loved those engines. The heat exchangers were easy to clean. Impellers were hard to get to as they were on the outboard sides in tight 44' Sundancer engine space (won't call it a room).


I crossed 1500 miles of Atlantic water from Naples, FL to the Virgin Gorda (USVI) with them, not one problem (I carried a lot of fuel in 55 gal drums). They were great engines. I'd buy 'em again any day.

 

[Juliet 15]

Oh yeah - they were turbo's with advietised 370 hp.

 

[RT Firefly]

Greetings,
Thanks all. You've answered my question(s). Easiest, at this point is to find a vessel more suited to my/our desires.


As a replacement to our LRC, I'm leaning heavily towards a "downeast" type boat. Our style of boating has changed and the days of long distance cruising are behind us. I would REALLY like to run in the low 20 knt range. Size-wise 25' to 34'.


The boat market is hot right now and as many "lookers" are finding out, good boats sell quickly. As well, my better 3/4 has opinions that differ from mine.... occasionally.

 

[DavidM]

Downeast hulls are not particularly efficient. I had a Cape Dory 28 with a 275 hp gasser. It would do 20 kts at wot. I also did an informal survey of other downeasters, see below. These are wot numbers and cruising will be 3-4 kts less. It will be very difficult to find a downeaster that will cruise in the low 20s. It will take a Cummins 8.3 at 450 hp to push a 34' to 20 kts cruising. Not many made with that much power.

Boat Make LOA Disp-Laded WOT- Kts Hp Actual

Cape Dory 28 9500 20 275

Mainship Pilot 30 12500 17 230

Mainship Pilot 30 12500 22.5 315

Duffy Atlantic 37 22000 22.2 450

Mainship Pilot 34 18000 19.5 370

David

 

[jleonard]

I agree with DavidM. That was the highest HP motor they made with the rotary injection pump. It's impractical to ask for more from that motor.

Not necessarily a rotary pump.
It depends on the year and configuration.
I repowered my old Mainship with one that had the Bosch "P" inline pump. Mine was the recreational rating of 270, but the commercial rated version was 250.
The limiter would be the coolant cooled aftercooler.
But you can still make lots of power in those engines, but you'd have to watch a pyrometer closely since a boat engine is always under load.
The pickup truck guys do all sorts of power upgrades and they are not all that expensive.

 

[RT Firefly]

Greetings,
Mr. DM. Oh dear. The mem-saab is leaning towards a "running shoe" boat.

Personally, I think they're f'ugly! Above image is example only.

 

[rslifkin]

With a downeast or planing motoryacht or sedan type, a cruise in the high teens is pretty easy to come by. 20s is a little harder. There are definitely boats out there that'll do it without going to an express cruiser, just not as many. And finding something under 35 feet that runs that fast often means gas engines.

 

[O C Diver]

For Downeasters, weight and beam are significant relative to speed. Wetted hull service from a wider beam offers significant drag. Weight from boat build and owner stuff also has a huge impact.

My balsa cored Bruno and Stillman 35' is lighter than most and with less than a 3:1 length to beam ratio a lesser wetted surface. With the Cummins 6BT 210 HP motor, it would run 20 knots, empty on the pin.

Changing motor to the Cummins 6CT 300 HP, increasing fuel capacity by 40%, and adding a larger diameter propeller, optimized the boat for my charter service. Unfortunately all the added weight reduced the empty top end to 18 knots.

Ted

 

[RT Firefly]

Greetings,
Mr. rs. High teens would work. Would like to run over to the Bahamas in less than 8 hours.


We, or rather I, have narrowed choices down to Albin TE series, Mainship, some custom models (https://www.yachtworld.com/boats-for-sale/make-judge/model-32/) and Back Cove to mention a few examples. I've even considered Glacier Bay catamarans and similar. https://www.yachtworld.com/yacht/2008-glacier-bay-3480-power-catamaran-7018251/ Thailand, while a beautiful country is a tad far to go.


Minimal to no canvas is quite high on my "must have" list.

 

[OldDan1943]

RT, dont overlook an AT34/36. Cummins QSB 5.9 with turbo. Advertised 380HP @ 3000RPM.
In theory, 18knts @ 3060RPM, 19.5gph
Of course finding any of the used ATs is next to impossible and new build, a waiting time is about 2 years+/-

 

[Ski in NC]

There are a few versions of the 6BTA that are rated around 250hp. The one with the rotary CAV pump is an older model (around 1980's) and was not particularly good. Inj pump basically maxed out, cylinder head with 9mm injectors was prone to cracking, some other cooling system weaknesses. If the engine you are looking at is this version, it is not a good candidate for boosting up hp. In fact, not a good engine to run hard at all.

In the 1990's, they fixed those weaknesses with the 270/330/370hp versions with the Bosch P pumps, revised head with 7mm injectors, cooling system fixes, etc. When those engines came out we in the industry figured if you can't make them live at 250hp, what are they going to do at 370?? Firecrackers, we figured.

Well, that was not the case. Even at 370, they held up very well.

Then the common rail QSB came out, up to 480(!!) hp. Got to be a firecracker!!! Nope, even those held up.

Cummins learned a lot in the several years when they introduced the first B and C marine engines. The first ones definitely had weaknesses. Later models, much better.

 

[kapnd]

What Ski said above ^.
I spent a lot of time and money just to bring an old 6BTA 250 to a point where I felt it was safe to push it a bit.
Upsized the raw water cooling system throughout, including intake, seacock, strainer, raw water pump, aftercooler, transmission cooler, heat exchanger and elbow.
rerouted an upsized the coolant loop and replaced the head.
Probably a bunch of other items that I can’t remember!
Still had the same hp for all that work, but was able to run it at 2200 for several hours at a time with no problems.
The rotary injection pump did fail, and switching to the inline pump was not an option, so got it rebuilt.
In retrospect, swapping it out for a 370 hp would have been a much better idea!

 

[jdecris]

I have two 6BTA5.9M1 250hp engines in my '91 Grand Banks 46. I've owned the boat coming on 4 years. The boat has never left Chesapeake Bay, and I'm the 3rd owner.

The motors have about 2100 hours on them.

I regularly cruise around at 12-1500 rpm and around 8-10 knots. Fuel burn increases dramatically above anything more.

The previous owner told me he ended each day on the water with a 10 minute run over 2000 rpm. I've done the same.

They always start up on the first cranks. Underway, I regularly listen, watch, and smell - on deck and in the engine room.

I've never had any problems with the motors.

 

[FF]

"and with less than a 3:1 length to beam ratio a lesser wetted surface."

The narrower the boat the more wetted surface at the same weight, tho skinny makes smaller waves, so should go faster.

The least surface area would be round , like a beach ball , but the speed would be limited.

A round boat, Would make a great Roomarian tho!

 

[rmidgett]

I'll second this. My 1996 Dodge 2500 Cummins has 350,000 on the odometer. Engine is reliable but noisy.

 

[ranger58sb]

Greetings,
Mr. rs. High teens would work. Would like to run over to the Bahamas in less than 8 hours.

We, or rather I, have narrowed choices down to Albin TE series, Mainship, some custom models and Back Cove to mention a few examples.

To avoid "running shoe" I'd guess Back Cove and MJM could offer decent candidates. Hinckley? Alden? Maybe some Sabre models, depending on what lengths they've offered and -- depending on how you feel about pods -- whether some of their earlier straight shaft models might become available.

-Chris

 

[North Baltic sea]

Hi,

You might want to ask this seaboard Tony, it may be a simple increase in power or else it's a more complex thing they know about Cummins machines.

Good maintained, the right propeller will not over prop, I have read these have reached high hours of over 20,000 hours, as have newer QSB engines same.

NBs