Cabo 47/48 C18 vs Man 800 V8

Would say if you have a lot of experience on Cats, that would be a major pro for Cats. Also the cost work on the Mans would be a con for them.
Local service centers in your area for both?

You know the Mans are expensive to work on? How do you know that? Internet talk, dock talk, current or old information. CAT isn't cheap either. I've heard all the stories, but I've owned and/or maintained 5 boats with twin Man's and been very pleased. Someone else will have to comment on performance on that specific boat. We do have 800's on a 44' Riva. At 78% load, 37 knots, 56 gph. At 60% load, 29 knots, 43 gph. The one area in which MAN will generally beat CAT is sound. We run 74 to 75 decibels at both speeds.

The 48' Cabo is a much better riding boat than the 47', the 47' had too much weight forward and tended to pound a little and was a little wet. They changed the fuel tank configuration in the 48' and I believe also added 200 gallons of fuel. The house is bigger resulting in an extra stateroom and larger salon.

Generally the speed difference in the Cabo's between the C18's and 800 MAN's was about 2.5 knots. 800 mans will burn 62 GPH at 80% from what I've seen and C18's will burn 76 GPH. Cat's are noisier and when you factor in the expense of having to replace the aftercoolers every 6 years, I'm not sure the MAN's are more expensive to maintain. Both are good engines.

The CATS are 2.5 knots faster at cruise and WOT. And, 1100 MANs would be 2.5 knots faster than the cats at 86 GPH at 80%. The C18's are 1000 HP, the Mans are 800 or 820 HP.

Folks, I'm afraid you are talking of different engines.
Afaik, the Rivarama is R6/800 powered, which is a completely different animal (6 inline cylinders, electronically controlled common rail) vs. the V8/800.
Not sure about the Cabo, but in any case if you are aware of what the load is, you can't be talking of the V8/800, which is 100% mechanical - and as such, there's no way to know the load factor.
It's actually impossible also to tell the real time fuel burn, unless retrofitted with some flow measurement kit like the Floscan.
I'm not saying that the difference between the electronic inline 6 and the mechanical V8, both capable of the very same 800hp, is going to be night and day. But there are differences for sure - also in the torque curve, btw.

That said, even with zero experience with the boats the OP is interested in, weight saving alone (more than 2k lbs) would make me lean towards the MANs. Whose more comparable Cat engine would be the 3406/C15 btw, not the C18.
I also like the fact that the V8/800 are their very last mechanical engines, and it's no coincidence that they are what I've got in my boat.
But some boaters like electronic throttles and digital displays better than simplicity and reliability - each to their own on that.

The 47' Cabo was too old to be built with C18's, the 48' is a different boat with a slightly different hull design and was first produced in 2003 and replaced the 47'. My figures are all with a 48' in mind and all motors read load and fuel burn on the display of the ones I ran. There are old articles and boat tests with fuel burn for the 47' cabo, did the tests on all of the boats they built as far as I know. So, the C18 1000 hp CATS burn 76 GPH at 80% load, the 800 mans, possibly 820?s common rails burned 62 GPH at 80% load and the Man 1100's Common rails Burn 86 GPH at cruise (there is a 2005 with 1100's for sale on YW). I have run several hundred Cabo's, mostly for Cabo Yachts and their dealers. But, it's been a very very long time since I've run a 47' or 48' Cabo and the actual cruise numbers are sketchy in my mind. I do remember running a 52' FB with C18s 1000hp with a hard top and it cruised at 26.5 knots.

Here is a yachting article in 2003 of a 48' Cabo with 1050 Man's and a 33 knot cruise/ 37 knot top.
https://www.marlinmag.com/boats/boat-reviews/cabo-48-flybridge/

There are only 2 Cabo 48s for sale on Yachtworld, both have MAN 1100 HP common rails. BUT, Horsepower is Horsepower, provided each engine is propped to achieve WOT, a 1015hp C18 is going to burn 76 GPH at 80% load, no matter what boat it is in. The Man inline 6 800hp Common rails are going to burn 62 GPH at 80% load. The only difference is the speed of the boat it is in.

I'm not saying that your numbers aren't correct, CJ - and the same goes for OB's numbers.

What I'm saying is that they can't be related to the MAN V8/800, which is the model the OP is interested in.
Btw, there's no such thing as an 820hp common rail MAN, either.
As I recall, their only 820hp rated engine was the last mechanical V10 - in the same way as the V8/800 was the last mechanical V8.

That said, I agree that for any given output, the differences between each engines and also brands can't be huge, as I also said in my previous post.
But within MANs, the R6/800 and the V8/800 are VERY different beasts, and even if their max output is the same (as well as the fuel burn at 2300rpm and 100% load is almost identical: 42 vs. 43 GPH respectively, in spite of the claimed fuel economy of common rail), the torque curves are completely different - and this is bound to affect the load.
So, even if it's impossible to measure the load with the V8/800, it surely can't be the same of the R6/800 (WOT aside, obviously).

The physical differences:


CAT 1001 hp, use the Prop Demand Data to compare fuel consumption (gph).

If you are looking at existing MAN installations:

What I am telling you is the 800 MAN common rails that Cabo put into their boats in the era that this boat was built burned 62 GPH at 80% for the pair. They may have been V8's, I don't remember. What were the initial 800 MAN common rails, V8's? I was the test boat Captain that spent an entire week with the MAN N. America President and head engineers on the 2nd set of 800 MAN common rails in the United States where we did seatrials all day, and they adjusted fuel curves/mapping and other aspects for all of the future 800's, boat happened to be a 43' Cabo. They were dead set on getting as much acceleration as possibly, but without too much smoke, because they were hell bent on getting away from the reputation of the mechanical ones (stink/smoke). Cabo used a lot of 800 mans in the mid 2000s, in a lot of different models 38'/40'/45' expresses, 40'/43'/48' FB.

There are two different MAN Engine models being thrown about, a V-8 and an Inline 6, both had ratings in the 820 - 800hp range.

The V-8 Versions started in the 43' and above, ranged from 800, 820 and finally 900.


The Inline 6 was rated at 800hp and was more compact and a perfect fit for the models 40' and below:

Pacblue, Thank you for clarifying that for everyone. I recently delivered a 2007 40' Cabo flybridge with 800 Man's which made me think they were all 6 cylinders......I've run a lot of 43' and larger Cabo's but it has been many years and 100's and 100's of boats in between.

You are correct on the Riva's. Now as to being impossible to measure load, it's quite possible to approximate it using any form of fuel flow system or even data collected. As to pre-common rail, I profess to virtually no knowledge. I'm not of that generation.

Nope, and this is the reason why I was positive that you had different engines in mind.

Their first CR engine rated for 800hp was the inline 6, aka "R6-800 CRM".
By then, the V8 (aka "D2848 LE403") had the same 800hp output, but it was still 100% mechanical.
A V8 CR rated at 800hp never existed, because the following year (as I recall), they introduced the first CR V8, aka "D2848 LE423", rated for 900hp.

Btw, I can also maintain that an 820hp V8 never existed.
@PacBlue: the table in your last post is taken from the brochure of the "D2840 LE401", which was their last V10 mechanical engine.
Which has been available for a while together with the V10 "D2840 LE403", rated at 1050hp and equipped with an early (non-CR) electronic control.
Afterwards also converted to CR, rated at 1100hp and labelled as "D2840 LE423", before they eventually phased out the V10 block altogether.

If you are aware of such instrument/method, tell me more about it, because I've never seen any load numbers for mechanical engines.
Even the so-called "prop demand" curves from engine manufacturers (which don't show the engine load anyway) are just estimated numbers.

See, the point is that any given engine, at any given RPM, can run at very different loads depending on MANY factors: the vessel type/dimensions/displacement, prop, gear reduction, hull and u/w gear cleanliness, even the fact that at some point in time you can be either going up or downhill through waves...
You name it, really.

Now, in mechanical engines, the governor does the job of calibrating the amount of fuel necessary to run at the RPM consistent with the throttle demand.
Very simple and straightforward, but there's no way to get a feedback on what the governor is doing, in sharp contrast with electronically controlled engines, where there's an ECU driving the whole process, which in turn means that it's "just" a matter of converting the digital signals generated to control the amount of fuel to be squeezed into another type of digital signal, meant to show - among other numbers - the engine load on a display.

What you are suggesting, i.e. extrapolating the load of a mechanical engine based on the fuel burn measured in real time through flow sensors (together with its RPM obviously, even if you didn't mention it), is fascinating in principle, but I suspect that the reason why that is unheard of, at least to my knowledge, is that it would be akin to use reverse engineering in the hope to regenerate a pig out of a sausage, if you see what I mean.....

But as I said at the beginning, if you are aware of any tool capable of doing that, I'm all ears.

Yeah, that MAN model designation caught me, 2848 is the V8, 2840 is the V10, and 2842 is the V12. No a very intuitive system, glad they changed it over.

No 820hp V8 ever existed.