Inspect the Engine Installation
Examine the following parts for wear and damage
Check for cracks, water/oil mixture, and puddles of water or moisture.
Engine motor mounts
Examine the mounts for cracks, misalignment, and distortions
Engine coupling shaft
Are these properly aligned? Check that they are bolted properly and the fasteners are in good condition
These should be soft and free of wear and cracks.
Electrical connections at the engine and batteries should be insulated. Look out for electrical tapes and naked wires
Depress each engine belt gently with your thumb. If the depression is over 1/4″, there is a problem.
Gaskets and Seals
Inspect the block, manifold, and oil pan for leaks and heat spots as they indicate overheating
Examine seals on the injectors, fuel lines, and lift pumps.
Check for leaks around the fuel tanks and fuel filters. What does the place smell like? Diesel, damp or oil?
Check the Dipsticks
Read the dipsticks of the oil sump and transmission gearbox
Check the color and reading in the second sounding. If the lubricant smells burned or appears milky or bubbly, the engine block might be cracked
Check the Impeller Housing
Examine the impeller vanes for wear and distortion
Inspect for Zinc anodes
Inspect the zinc anodes on the propeller shaft or hull, as well as in the engine heat exchange if they are used
A fully compromised shaft zinc can’t perform its function to prevent corrosion of the drivetrain, so that is a serious problem
Test the Engine Live
Run the engine at full throttle to identify hidden flaws
Power the engine to the maximum and check for the fluctuations of the RPM, oil pressure, and water temperature.
Also, examine the stuffing box for leaks, check shaft alignment and hose-to-fitting seals for leaks
Source: MaintainX (Community Member)