1350 hp MTU 2000 M90 Vs 1000 HP Cat C18 on 30 m Benetti. Which is Best

I ran a then new, 30 ish meter benetti (98'), but it had MAN's and was probably a 2017. It seemed to have adequate power but was more HP. I'd say the C18's are more reliable, but have to change aftercoolers in them every 6 years. But not sure if the C18's would be enough power for that yacht. Mtu's will be a little quieter.

Underpowered with either so I'd choose the MTU 1350's.

It's a displacement hull so only does 12 knots no matter how much power you give it. Trust me, the one I ran had 1400hp MAN's I think, and I tried

I'd still go for the MTU's.

Look carefully at the service history , that’s probably going to be the decider .How ever if equal then the intercooler debacle with CAT s are inho best avoided , so it swings to MTU or MAN if possible .

The C18 is an excellent motor, very very reliable, provided you replace the aftercooler every 6 years.......probably less expensive to maintain over time compared to MTU/MAN, IF you follow the service requirements by the book (cleaning all the coolers every 2 years specifically).

Who does follow the MAN service schedule by the “ book “ ??
In France and Italy the certified MAN agents themselves don’ t even .
Assuming all temps / readings are within spec
Maybe perhaps with new - re warranty issues , but once out of warranty folks just do a full strip as and when .
Depending on the instal a lot slowly drain down when stopped so the coolers never really are left to pickle .

So if you remove the cost of biannual strip then .......?

The hull anodic protection and separate 24 v ( own starter + electronics ) isolation of the MAN system ensures a more guaranteed protection from galvanic protection .

There’s no pencil anodes to risk disappearing out of sight or drying out , or multiple dissimilar metals in the cooling component construction with MAN / MTU ........unlike CAT s .

As you say CAT ( law suit losses ) now suggest the after coolers are a throw away part , timed for what ever 6 y ?
That’s scary the thought of water entering into a cylinder through no real fault of the operator .

Given a choice which is what this thread is about it’s about an informed choice .
As said the SH needs going through .

Hear of cooling components corrosion here in the Med with CATs C12 , C18,s C32 s from about 2005 up.Boats being stuck away from there home ports awaiting fixes .
MAN s the odd sensor, a 48 hr bolt on fix and you are on your way , just run them until it can be fixed .
Point is no cooler corrosion if the hull anodes ( easy to inspect and replace ) are good .

Plus when you deduct what it would cost to normally clean the coolers in that time period, it's really not that more expensive. I haven't found MAN's to be terribly expensive to maintain either.