How many hours is a mercruiser 350 good for?

I know this question is highly dependent on maintenance, how hard and often the boat is run, etc. but is there a ballpark average for how many hours mercruiser 350's most commonly get on their hourmeters before needing a complete rebuild?

 

You ask a hard question as a true answer would require the need to know how it has been maintained and how it has been run. Mercs are not heavily built when compared to Crusader engines which if well maintained can go for 15-20 years. Small plane engines must be rebuilt in the range of 1200-1600 hours depending on make and they are usually well maintained. You can do a test (diagnostic) and find out some data or even pull a head. Also you can put clean oil in it with new filter and run it several hours to see if it remains clean. Also check old oil for any metal filings. But to give you a number of hours W/O knowing more would be misleading you.

 

Thanks rasorinc.

A friend says "1000 hours" as a general rule for the lifespan of a gas mercruiser inboard/sterndrive engine. I understand what you say though.

If compression is good, oil looks fine, and a mechanic can't find anything immediately wrong though, what I'm after is a ballpark lifespan for an older boat if I continue to care for her properly. (and a ballpark to use as I do some preliminary looking at ads for used boats)

For example, one boat I'm looking at has 200 hours on the mercs. Another less expensive boat has 600 hours on the engines, but the owner assures me they run great, have no problems, and they look spotless indicating they've been maintained by someone who cares. If I plan to put 100 hours on the boat I get per season, what I'm looking for is some ballpark idea so I can figure how much more are the engines with 200 hours worth to me than the engines with 600 hours already? (i.e. in an average case if they're in good shape now, how long will they live for most people before major money is required to rebuild or replace?)

 

Use your eyes and ears. A well maintained engine with 600 hours may well be in better shape than one with 200. Younger owners tend to allow for no warm up etc just roar off. Taken care of you should be able to get 2,000 hours. Go for the best cared for boat--that tells a lot.