do you tune up these efi engines by time (yrs) or hours?and what parts ( plugs, cap , rotor , wires, )

Mercruiser suggests an engine tuneup every 100 hours. Spark plugs, cap, rotor, and water/ fuel separator filter. Never needs wires.
Change engine oil and gear oil every 50 hours.
Remove drive and grease U joints, splines, and gimbal bearing every 100 hours.
Dennis Moore
Mercruiser Master Tech

Dennis,

You said something in your reply that strikes me as funny. Keep in mind that I am not a professional mechanic and I you've probably forgot more about Merc products than I'll ever know. But, you said "never needs wires". Really? Are you saying they never wear out? I was going to have my engine completely gone through like above. If I don't need to have the tech replace wires I would like to know for sure.

Can you elaborate a little on this?

Buck

Go to any Mercruiser dealer and try to buy some wires for an engine. Nobody stocks wires because nobody ever replaces them (if you do find some, the package will be pretty dusty because they have been sitting on the shelf a long time).

The water cooled exhaust manifolds and cool engine compartments keep the spark plug wires in good shape, unlike a car or truck engine.

The biggest problem with most car and truck engines is leaking valve covers from burned valve cover gaskets (again, the hot exhaust manifolds) dripping hot oil onto the wires. The cooler exhaust manifolds don't create burned VC gaskets on a marine engine.

The same holds true for the belts and hoses in the cooler engine compartments of a boat. They usually last the life of a marine engine.

I am sure that this is a controversial subject, but the fact remains that very few spark plug wire kits are sold in the marine industry.
Sincerely
Dennis Moore

Makes sense to me. I have learned something today.

Thanks Dennis. We are very lucky to have you here.

Buck

I don’t want to in anyway step on Dennis’s toes. He is correct in stating that wires should never need replacing. However drive belts will eventually. This is mainly because over time they will stretch as they do in all applications and most people will not know how to properly inspect & tension them if they bother to check them at all. Once they stretch they will begin to slip thus heating them up and causing them to break down. Now yes the marine engine environment is a lot friendlier than an automobile but you need to remember that marine engines turn a lot more RPMs. Also if you leave your boat set up for a long period of time in cold weather the belt will take shape, and will not want to move when you go to start it for the first time. You can keep them forever if you want to but I wouldn’t want to be caught offshore with a shredded belt would you? (especially a serpentine) In my opinion including them in every 100 hour tune up is cheap insurance. Cost you less than a tow anyway.

No disdain intended Dennis, just wanted to share my experience

Roby