Looking at a 1990 45C, Suggested details to look into?

Just a question; Are these the 6V92TIAs?
Some higher (620?) HP, DDEC controlled engines?

We do need the HP or or better model number (TI, TA or TIA) to offer the closer burn numbers.
The safer 6V92s started way below 300 total HP.
75HP per lung was still considered safe.
80 to 90HP per lung was high performance (short life).
Over 90 and beyond 100HP per lung is insane (No Life).

Give us the tune data, we can answer your question better.

Still a press on long life.
If it has the straight log exhaust manifolds, then I'll call it the 550HP.
Here is a pirated copy of the DDC cut sheet. You want to look at the prop loaded RPM / GPH figures.

Are you DDC Savy??

I luv Vikings.
I luv Detroits.
High performance Detroits (92s) can stretch patience and checkbooks if your not ready.
There is no fuel economy in a Viking 45C. No matter what engine.

Shopping for a Detroit boat with 92s;
#1
Is there a good Detroit tech or shop close by that can work on your engines?
The better Detroit techs are dying off of old age.
Your old DDC tech will spill blood in your bilges. Find him and become best friends now.
Don't feel pregnant;;
I tell MAN shoppers to find a good shop also. Better MAN techs are also hard to find in some areas.

#2
No stone un-turned surveys.
Every lung inspected. A side cover plate is available for each lung. Some are hard to get to and will cost more for the surveyor,, but worth it.
Looking for a nice hatch pattern to prove not over fueled or abused. When you find that old DDC tech, go over this before the survey.

#3
1500 hours each from what? Top end? Complete including liners? Out of the boat or in frame? Dyno'd? Or just an aerosol overhaul?
Without receipts, it did not happen properly.
Oil lab history? Really helpful on a 92. Ensures no coolant in the oil.

#4
Find the factory specs. Prop size and performance numbers. So many repaired props loose diameter and performance.
During your survey and sea trials, ensure all is close to factory specs (or better?).

IMO
71s take up more room but are more forgiving. Dry liners are more forgiving abet less bang per lung.
Is there a 45C with 71s around?

Then, while the engine tech is checking out the engines, The other surveyor is going thru the boat.
Better surveys may take 2 days per surveyor. That is a lot of boat to check, Don't rush them.

Please search and read the many Detroit threads here on YF.
Tomorrow, I'm hoping more Viking kids will tap in on your thread here.

1500 hours on a 33 year old boat?
Never overhauled?
The cylinder liner O rings can't last that long on a shelf, half that time in the engine just sitting there.
This is getting scary.

Please re-read what you have typed.
33 year old 92 engine. 1500 hours, never rebuilt.
I'm no expert either, only been working on them my whole life.

Rusted exhaust valve seats and valve stems. Possibly even a stuck exhaust valve.
It may start up but that rust on the seats may turn to hot spots and burn up the valves.
Been there.

Would you have the internet addresses for these boats your looking at?
Some of us may even know the boat your looking at.

ie;
https://www.**************/yacht/1988-viking-45-convertible-8690602/

Here is where an ole DDC tech shines. Pull some side covers off now and with a bore scope, look up to the valves and take a peek.
Then hand bar the engine over to examine the other lungs.
Baring over by hand also helps eliminate a stuck valve slamming against and damaging a piston top.

A proper valve and seat repair does involve pulling the heads.