Thoughts on Cummins 6BTA 5.9

[5teve]

Hi Guys

Just looking at options for a boat (as our other offer is not likely to be accepted on our original boat choice) and have come across a friends friend with a Riviera 38 - 1990 built with twin cummins 6bta 5.9's - 2100 hours - I currently know nothing else apart from the owner is a diesel mechanic or marine mechanic.. we are thinking about going for a look as its well equipped - just needs maybe a few changes to the interior.

Whats the general consensus on the motors - typical rebuild hours etc etc what would we need to look out for?

Whats the fuel consumption like on them (bear in mind we were looking originally at a 380hp Iveco single engine boat that cruised about about 25-30lph) I think the boat is about 11t total weight.

Thanks in advance (again)

Steve

 

[burgundyben]

Possibly the most common 'litre a jug' engine there has ever been, regarded as the most robust, clean running, low service cost.

I doubt in this power node there is any better choice.

 

[superheat6k]

As a Dodge Truck or Bus engine I would expect these would do literally 1/2 million miles, so that must equate to at least 10,000 run hours at 50 mph.

In a marine environment the life will be subject to the care that the boat's owners have taken with the maintenance.

Mine are a bit grubby, but seem absolutely sound although only ~ 900 hours.

Cummins are great for getting spare parts very quickly, and are comparable I guess with VP on price. But service items are readily available from other places for peanuts.

If you do end up with it I have a good service manual on PDF for ground equipment maintenance with the same engines.

 

[benjenbav]

I had the same engines in an Aquastar which I owned for approximately 7years. I was very happy with them.

 

[AndieMac]

Hi Guys

Just looking at options for a boat (as our other offer is not likely to be accepted on our original boat choice) and have come across a friends friend with a Riviera 38 - 1990 built with twin cummins 6bta 5.9's - 2100 hours - I currently know nothing else apart from the owner is a diesel mechanic or marine mechanic.. we are thinking about going for a look as its well equipped - just needs maybe a few changes to the interior.

Whats the general consensus on the motors - typical rebuild hours etc etc what would we need to look out for?

Whats the fuel consumption like on them (bear in mind we were looking originally at a 380hp Iveco single engine boat that cruised about about 25-30lph) I think the boat is about 11t total weight.

Thanks in advance (again)

Steve

The Riv 38 is and has always been regarded as good property, and in Australia particularly with the Cummins option, resale should be good. There will of course be the usual maintenance issues regarding any vessel of this age and a proper survey of the hull and all machinery required, regardless of whoever has owned the boat.
I operate commercially the later QSB versions of these engines and as superheat implied, we replace every 10,000 hours, they start using small amounts oil around 3,000 hrs, mind you we average 1500 hrs per 9 month season and they run at 2450 rpm (out of a max 2800) for most of the time.
Recreationally you will never go near those hours, you will do some hours when the boat is first acquired of course but generally after a few seasons the hour usage will reduce as the novelty wears off, as you can see by the hours clocked up over the life of this particular Riviera.
Good luck with the deal.

Edit; fuel consumption in this hull should be around 70 LPH for both engines combined at cruise speed and revs, which is par for course in this size and weight. You can run at displacement speed and use a fraction of the fuel if the sea conditions are good and you have the time, as an option to increase your range.

Our 15 tonne semi-D cat (inefficient hull) with 60 passengers on board uses 100 LPH (both motors total) @ 2450 as a worse case scenario

 

[Paul&Ness]

The man you need to seek advice from is Latestarter1 he is a bit of an authority on Cummins engines and has a pretty extensive knowledge of the pros and cons.

 

[5teve]

Possibly the most common 'litre a jug' engine there has ever been, regarded as the most robust, clean running, low service cost.

I doubt in this power node there is any better choice.

Thanks Ben... I dont see too many boats of this kind powered by Cummins for sale... mainly VP - probably the hold they have in Aus.. so good to know.

As a Dodge Truck or Bus engine I would expect these would do literally 1/2 million miles, so that must equate to at least 10,000 run hours at 50 mph.

In a marine environment the life will be subject to the care that the boat's owners have taken with the maintenance.

Mine are a bit grubby, but seem absolutely sound although only ~ 900 hours.

Cummins are great for getting spare parts very quickly, and are comparable I guess with VP on price. But service items are readily available from other places for peanuts.

If you do end up with it I have a good service manual on PDF for ground equipment maintenance with the same engines.

Thanks SH from other reading they seem fairly similar to the Iveco's I was looking at - bus engines at heart - so pretty strong normally. Good to know lots of 3rd party items available. Hopefully if the owner is a diesel mech - they should be well looked after.

I had the same engines in an Aquastar which I owned for approximately 7years. I was very happy with them.

Cheers for the feedback from 7 years.. happy is good

The Riv 38 is and has always been regarded as good property, and in Australia particularly with the Cummins option, resale should be good. There will of course be the usual maintenance issues regarding any vessel of this age and a proper survey of the hull and all machinery required, regardless of whoever has owned the boat.
I operate commercially the later QSB versions of these engines and as superheat implied, we replace every 10,000 hours, they start using small amounts oil around 3,000 hrs, mind you we average 1500 hrs per 9 month season and they run at 2450 rpm (out of a max 2800) for most of the time.
Recreationally you will never go near those hours, you will do some hours when the boat is first acquired of course but generally after a few seasons the hour usage will reduce as the novelty wears off, as you can see by the hours clocked up over the life of this particular Riviera.
Good luck with the deal.

Thanks Andie - Yeah it seems the older Rivs, although I think classed as a "wet boat" (they all are in WA) seem to be well built - not a great layout though.. but build / weight / ride is more important to me. We were orginally looking at a 33ft Commodore, which we really like (35ish ft actual size) but I doubt our offer will be accepted as it needs some work doing. We currently do 200 odd hours in our existing 6m Tinnie per year - so would expect to do more in a larger boat. Its our escape from our business, but also a floating office if needs be. We tend to put a lot of hours on in Whale season - Aug - Nov too.

So at 3000 hours using small amount of oil - i'd assume nothing much to worry about? I have landrovers also - so used to oil usage - Are they rebuildable - ie linered etc? or is it not worth it and just keep pushing to the point where they just need replacing?

The man you need to seek advice from is Latestarter1 he is a bit of an authority on Cummins engines and has a pretty extensive knowledge of the pros and cons.

Thanks Paul - yep from my searches - he is THE authority - but general advice can only be garnered until we decide to have a look (our budgets dont quite align yet) and then I can get stuck in with more details - history serial numbers etc etc..

Steve

 

[AndieMac]

They have used the "wet" boat term for years, the best riding boats are the wet ones, besides as soon as you trim the bow down of any fast boat in rough conditions it's going to get wet, make sure you have Rainex-ed the windows and enjoy the ride, ha!

I'd stick to the Riv as a choice, refurb the interior, you will really appreciate the manoeuvrability of the twin screws compared to the single on the Commodore for a start, besides being a known commodity.

As you know Latestarter is the guru, not sure about the rebuild scenario, would rather hear Paul's opinion on that.

 

[5teve]

yeah makes me smile - Our boat is apparently a dry boat... cant say that it has been and it certainly doesnt ride nice in the chop - awesome in a following sea tho!

The commodore is a surprisingly nice boat - WA built and heavy for its size - at around 7.5-8t - built for our conditions apparently - very little known about them apart from they are still being build locally (the 33/34 version) on request very deep keel keeping them stable, and pretty nicely finished internally - the 33ft one we were looking it had 4 fixed berths in 2 cabins and awesome engine access.. single screw doesnt worry me much.. as it would be kept in a fairly spacious ocean marina. The commodore is also a 2002 - and as they are an 'unknown' boat - the price reflects that also - Currently though it is suffering from the being stood to death syndrome and the owner thinks it is in A1 condition.. I reckon around 10k to sort out for stuff I have noticed that I class as essential for reliability.

The riv is older - but yeah better known and i think the older ones are better built hull wise - again not too much info on the older ones around - but slowly researching them. Bigger beam also (commodore is 3.5m) so quite a bit more room by the looks of it.

Steve

 

[Latestarter1]

Steve,

Agree with vast majority of the comments on this thread but just a word of warning........

We must have serial number and find CPL. There was CPL 970 6BTA which had Denso fuel pump without LDA and a badly designed (welded) SWAC (Sea Water Aftercooler). The welded Modine SWAC was a real crummy design, absolute time bomb which was redesigned by guys at Darlington using a U.K. manufactured Serck unit and the same basic design is still in use on current QSB's.

Hard to believe that Americans ever put a man on the Moon when you look at the design of the Modine SWAC, it fails catastrophically dumping sea water direct into the engine. Cummins provided kits a special pricing to retrofit CPL 970's however I still come across a few 'rogues' with the Modine units which are potential time bombs.

Replacement 'Serck' units from Cummins are no longer subsidised and my guess knowing Australian parts pricing is probably about Au$3,000 a unit so a picture as well as ESN is vital.

Older CPL 970's had a Denso fuel pump with no LDA and needed propping with care as they could black smoke going over the hump, later 970's incorporated Denso with LDA.

Some pictures and I can put your mind at rest.

Interested by comments by Andie Mac, 10,000 hours life to overhaul for QSB running constantly between 2,450 rpm (70% load?) and rated in commercial service sounds about right. Out of interest dropping to about 50% load around 2,000 rpm continuous takes life to overhaul out to at least 17,000 hours.

 

[MapisM]

Hard to believe that Americans ever put a man on the Moon when you look at the design of the Modine SWAC

Well, it's not like everything has always been flawless at NASA, in fact... :nonchalance:

 

[AndieMac]

Latestarter: yes you are spot on, 70% load on the 350 hp versions. We have to run at these revs (and speed) to complete our cruises within a specific time frame.

 

[Latestarter1]

Latestarter: yes you are spot on, 70% load on the 350 hp versions. We have to run at these revs (and speed) to complete our cruises within a specific time frame.

Out of interest valve stem oil seals were identified as being the source of oil consumption on QSB 5.9's a good few years ago, and were modified to a more robust design for QSB 6.7 and the newer seal superseded the earlier one in QSB 5.9 gasket sets. Easy to change seals in a couple of hours without disturbing cylinder head.

 

[MapisM]

Latestarter: yes you are spot on, 70% load on the 350 hp versions.

Wow, I didn't remember that you've got only 350hp each side, on your cruising cat.
Considering also how loaded she is when full of passengers, the performance is remarkable.
Just a thought, doesn't the 6.7 fit in the engine room?
I would guess the overall running costs shouldn't be higher, if not even a tad lower, with some less exploited engines...
LS1 surely knows better than me, anyway. :encouragement:

 

[Latestarter1]

Wow, I didn't remember that you've got only 350hp each side, on your cruising cat.
Considering also how loaded she is when full of passengers, the performance is remarkable.
Just a thought, doesn't the 6.7 fit in the engine room?
I would guess the overall running costs shouldn't be higher, if not even a tad lower, with some less exploited engines...
LS1 surely knows better than me, anyway. :encouragement:

QSB 6.7 is a bit more tubby, larger heat exchanger as it goes from 227hp to 550hp all on one CPL.

I know of a pair of QSB 5.9 380's in North Sea wind farm support support vessel which had done 17,000 hrs last time I spoke to operator, they are doing oil changes every few months as operation is intense.

Because 6.7 became a bit obese Darlington have done a new QSB S/L model at the request of certain yacht builders in Italy so it has the same envelope as old 5.9 and is in fact very close to Volvo D6 envelope however S/L version does not go all the way to 550hp

 

[AndieMac]

Out of interest valve stem oil seals were identified as being the source of oil consumption on QSB 5.9's a good few years ago, and were modified to a more robust design for QSB 6.7 and the newer seal superseded the earlier one in QSB 5.9 gasket sets. Easy to change seals in a couple of hours without disturbing cylinder head.

Thanks for the heads-up LS, that's certainly a good lead, cheers!

 

[AndieMac]

Wow, I didn't remember that you've got only 350hp each side, on your cruising cat.
Considering also how loaded she is when full of passengers, the performance is remarkable.
Just a thought, doesn't the 6.7 fit in the engine room?
I would guess the overall running costs shouldn't be higher, if not even a tad lower, with some less exploited engines...
LS1 surely knows better than me, anyway. :encouragement:

I reckon the old boat will get changed for a new one before any serious reconfiguration occurs, but as usual it's always really interesting to hear LS's words of wisdom on these matters.