Difference between Cummins Engines

I am looking at two 2005 boats. One has a 6BTA5.9 370hp Cummins engine and the other has a QSB5.9 380 hp. Aside from the extra 10 hp, are these two engines essentially the same in term of set up and performance? Is one more or less rugged than the other?

The QSB is the slightly newer version of the 6BTA. So 1 generation newer with EFI instead of mechanical injection. The QSB will run cleaner and is quieter, but performance wise they should be similar.

Should I assume that fuel consumption would be comparable, or is EFI measurably better?

Looking at the fuel curves published by Cummins, I'd say the QSB might have a slight efficiency advantage, but nothing significant. They don't look drastically different or anything.

The QSB should be a bit more efficient but it also comes with electronics on the engine which may or may not be good, depending on your preference.

Good info. Thx

Comodave - can u give me some insight on preferences? Since these boats are both singles the number 1 preference for us is reliability assuming similar maintenance. What are the preferences folks have one over the other?

Personally I really don’t have a preference however my engines are all mechanical. We were coming home and we blew a fuse on one of them and didn’t find out until after we had docked and went to start that engine and it wouldn’t start due to no power, but it kept running until we had shut it down. However some people love the electronic engines, more efficiently, more information about how the engine is running, etc. i guess that the electronic engines need more specialized training and equipment to work on them. Good and bad...

Comodave said:

Personally I really don’t have a preference however my engines are all mechanical. We were coming home and we blew a fuse on one of them and didn’t find out until after we had docked and went to start that engine and it wouldn’t start due to no power, but it kept running until we had shut it down. However some people love the electronic engines, more efficiently, more information about how the engine is running, etc. i guess that the electronic engines need more specialized training and equipment to work on them. Good and bad...

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Comodave,
Do you have 6bt mechanical injection? Mine have an electric fuel solenoid that must have power or they won’t run. Occasionally I’ve tried to find a part number for a “normally open” solenoid so they would continue to operate in a ‘black ship’ situation but so far no luck.
Thx
Duncan

QSB is 0 smoke on startup. I started mine yesterday 33 Deg. , no smoke.
The Db level is also lower. Although they have some sensors , if they fail the engine is not going to stop. I have never had a failure. Priming the fuel system is simply turning the key. Both engines will give you long life and low maintenance. I think if you run both , the Qsb is more friendly.

I have Lehmans.

I had an electrical problem that cut power to the solenoid on an old 6BT. Used safety wire to hold it open and continued on. KISS Keep it simple stupid. I love the old pre-emissions engines. There are fewer things that can fail.

T210DRVR said:

I had an electrical problem that cut power to the solenoid on an old 6BT. Used safety wire to hold it open and continued on. KISS Keep it simple stupid. I love the old pre-emissions engines. There are fewer things that can fail.

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Hi Jim,
My fuel solenoids are internal and inline, no moving parts to wire open.
There is a mechanical fuel cut off on the fuel injection pump but that would involve both disabling the solenoid and attaching an external solenoid to pull the cut off lever.

Duncan

Something not mentioned here is the difference between to two for regular maintenance stuff, i.e. oil and fuel filters.

With all of today's electronics, its nice to be able to tie your engines to all the electronic world. Full enclosure, I have 3208 T/As mechanical.

Hi, I have so far only good experiences QSB 380hp machine, it is a quieter, more fuel efficient and the best I can drive it low+ 800 rmp for long periods of time without worrying about the glass transition and coal (I have asked this thing Cummins factory) At the moment I have 1500 hours of which + 1000 in a few years.


I have read Seaboard Forum Tony A one checked the charter boat with engines of about +17,000 hours without any major problems.


The only thing I replaced with the machine is the raw water pump sherwood, I replaced the Sea max with a longer service interval.


Normal maintenance is made easy, eg changing the fuel filter, since venting can only be done by turning the key, the electric pump does the job.


NBs

We have Cummins 6CTAs, and I tink I'd slightly prefer the newer electronic QSCs... but that's partly because I'd like to be able easily get more real-time engine data presented. I guess the horsepower increase is larger than with the BTA to QSB series, and that'd also be decent for our type boat.

But I like what we've got, too.

-Chris