8v92 turbo 720HP longevity

I have a set of 16-92's 1450 HP so some of my experience may help. Make sure your water pumps have clean screens under the boat or a clean filter inside the ER if that is where it is. Check the impellers at least yearly and buy an impeller puller. If one blade is cracked then change the impeller- you don't want to be taking the system apart to find the broken off blades downstream blocking a cooler. Make sure your heat exchangers are clean; the main units and the PS and fuel coolers. Make sure your charge air coolers are clean. Don't fall behind on sacrificial zinc changes. Change the racor filters and secondaries on schedule. Flush and replace the coolant every three years. Make sure your props are matched to the boat so you reach your full load rpms; you don't want to over load your engines and have excess black smoke at speed. Keep the bottom clean. Install a set of block heaters (coolant) and keep them on all the time. Change the oil between 100/150 hours, or better yet install a set of aftermarket bypass (3 micron) filters. I have 3000 hours SMOH on one main and 1000 SMOH on the other and they start right up with no smoke and run very smoothly. I cruise between 1700-1850 rpm and only make top speed runs when I know the bottom and intake screens are clean. I'm confident with a careful eye and attending to items before they are an issue I'll get at least 5000 hours before any type of overhaul is warranted.

Bamboo is on point....

92 series have wet liners which require special attention to the cooling system and PH

There's a Bertram across the pier from me with 8-92's. When they start them up it's thick smoke city for a good three minutes. Everyone in the marina and restaurant sees it. I start my engines and there is a slight wisp for a few seconds; plus I don't need to warm them up (as much).

Check the zincs yourself if you are buying the boat- if they are all good either they just changed them or they are on top of it. Look at the oil level; is it in range? Check the coolant level- and color. It ought to be pinkish. Check the engine bed- does it have oil leaks? If it doesn't then the engine is out of oil

You are right- don't run them hard and do all the maintenance. Other captain may chime in with other advice, but that's how I care for my engines and they treat me very well. I have non DDEC versions and love them.

I would say 3000 hours between majors on those, sometimes less. Aside from changing the coolant (additive) every 2 years. MAKE sure the boat is not overpropped. 8v92's live a very short life is they don't turn up to top rpm at WOT with the boat loaded, even 30-50rpms over is good.

There are two schools a thought at running them. Some say cruise them at 1850rpms (granted most of these people don't realize the boat is overpropped by 100 rpms either. The other more modern school of thought is make sure they're propped to achieve RPMS to 50rpms over and run them harder such as 1950-2000 rpms where the boat is fully on plane and they sound like they're running easy and maintaining a steady speed over ground (keeping EGT at 850F or below) and they run cleaner and the liners don't get washed out by the usually too big injectors. We ran a 1987 63' Ocean this way (towing a 35' Marlago) a lot of time and got an honest 6500 hours on a set of 12v92's. I've never seen it on the boats I've seen run easy (1850), and 12v92's I see go 1000 hours between majors on those. One 58' Striker 1988 I managed had 8 sets of majors by 2004 with 12v92's and was always run 1850-1900 rpms. Problem was at those rpm's it wallowed between 17.5-21 knots as it fell onto and off of a full plane......at 1950-2000 rpms and ran a solid 22.5 knots and stayed there.......92's don't like changing load factors and being loaded and unloaded (varying cruise speed over ground). They seem to do well in boats that they cruise it at 25-30 knots for the reason sea state has less of an effect on cruise speed.

I much prefer 71's and agree they're more forgiving.