Do I need to get a service to my MAN 1100 every year?

Perhaps MAN has loosened some of the schedule although they're still more frequent for service than others. We currently have or take care of 4 sets of MAN's and they range from 4 to 6 years old. We did have another set briefly.

As Ralph describes they are all on performance boats cruising at 35 knots, WOT of 40 knots. We don't baby them on the water. They've consisted of 1 pair of 800's, 2 pairs of 1000's, 1 pair of 1200's and 1 pair of 1360's. No failures in service. Very pleased with all. All but one boat has been Riva's. One was a Sunseeker.

I don't follow that. Derated, I don't believe, has much to do with maintenance items. Oil is going to lose viscosity whether its in a derate engine or not, impellers will take a set, injectors will lose a spray... what about non engine items? When do you change the dripless seal? Every year because it takes a set, or near its expected life?

I think the point we are all making for the OP, is that don't skimp on maintenance - when in doubt change it., and climb all over that engine, squeezing hoses, looking at the hidden areas with a mirror and light, run your finger over the air seps see how it come back, check the battery water - a thousand things. But. learn what the expected life of the various components of your boat are - mechanical or otherwise - and perform reasonable preventive maintenance. I just don't believe that at 2 years or 400 hours for replacing injectors is reasonable. But, changing your oil every year is a gimme.

Who knew the expected life of a 8D battery is roughly 2-4 years and when you replace you replace the bank - I didn't until about a month ago, and thank you for that lesson.

I referenced commercial applications for a different operators perspective, as the OP was looking for input, maybe even some outside of the typically published service manual box.

But modern de-rated high use diesel engines and hi-power low use diesel engines still share common design architecture and engineering. Pleasure craft diesels have a plethora of Manufacturers MTTF and MTBO studies behind them to give the consumer some credible baseline service schedules. It is really up to the owner/operator to make their own maintenance decisions outside of warranty, and it just comes done to personal preference. Baby them/pamper them? Sure, extend high ticket service events beyond published hours when you are only accumulating 100 annual hours per year? That is a real option too.

Extended service requires good record keeping and monitoring. If you are the type that would not routinely have your oil analyzed and your oil filters cut in half for inspection during a routine oil change, maybe extended service shouldn't be your first option. It comes down to how comfortable your are with your own engines, how well you can inherently tell if their behavior has changed between trips or if you are totally reliant on a more experienced review of your engines.

And to how willing you are to take the chance that you might be wrong in your review of your engines and their service needs.
The cost of servicing more frequently than absolutely needed is small compared to the cost of being too late with service or of maintaining an engine poorly.
Most look at just the cost of the maintenance itself. We put an extremely high value on any loss of use and especially failure while being used. I'd far rather spend extra time and dollars at a convenient time, than deal with an urgent need at an inconvenient time.

MAN and most other recreational pleasure craft diesels call for an annual service and for very good reason. I'd change the oil/filter, fuel filters, clean air filters, annually. Every 2 years on a MAN you want to change the coolant, heat exchanger caps, impellers. Do a valve adjustment every 5o0 hours, I'd do the 1000 hour service every 4 years. All on low annual hour motors. BUT you do not want to skimp on annual oil changes, impellors every 2 years or coolant every 2 years on a MAN.

Agreed 100% - they are excellent motors IMO. Did we lose the OP?

Oil should be changed annually because the oil's additive package deteriorates over time and gets further used up holding contaminants in suspension. This is not related to engine operation (mileage) just time.
This includes the oil filters and may as well change all the fuel filters .
I tend to change the air filters every 2 years or sooner if they darken .

The belt I check for cracks and correct tension .
Impeller inspect and if signs of cracking or wear change .

Injectors I plan on doing at the 1000 hrs which at the current rate of approx 80 hrs / year will be in 3 years time .

They are 2003 2876 I6 ,s - 700 Hp and have been faultless in the 4/5 seasons I have had the boat .
Tend to run at around 80 % load all day 1800 and somthing rpm depending on prop hygiene.

I think the oil Fq interval is the key to longevity .

Another factor is running at the correct temps .My set up rapidly cools if run at displacement speeds , so i prefer planing speeds .I,am in the correct EGT camp north of 550 , south of 625 range .To minimise Agglomeration and keep the rings nice n tight .

What the OP has not clarified if the 100 hrs are at D speed or P speed like the guy above with the 21 year Post 50 + fresh oil / year running @1850 rpm .
That to me sounds like a winning formula- Hence his 2400 hrs or what ever .