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For all you marine tech's out there, what is "alot" of hours for a 4 stroke outboard? I have heard that over 1000 hours is not a lot, given that the motors have had regular service, etc...Any input would be appreciated.
Not really a tech, but I do have a 2002 Yam F225 with over 1500 hours. The last service indicated no loss in compression, & outside the normal oil changes, lower unit service, water pump replacement, timing belt replacement, etc., the only problem has been to replace a seal in the main tilt-trim cylinder.
1000 hours is not a lot of hours on a 4s. At a minimum that would be about a quarter of the life of that engine. At a couple hundred hours a year that gives you a lot of life left in that engine. In addition to the regular maintenance if you properly manage the ethanol issues you should have many years of happy boating left.
We have seen engines (mainly in commercial service) with over 6 and 7000 hours service.....These engines are generally used very frequently and have perfect maintenance schedules.
Don't own one, but the subject is interesting. I've heard the "claims" of 5,000 hours or more as well.
Granted, it can happen.
But, is there anything different about the design/technology of an outboard 4s- as compared to an inboard- that backs up the claim? Typically, and inboard with over 1,000 hours (particularly if run hard) is regarded as being nearing time for a rebuild.
Those old design inboards were not made to be immersed in a bilge full of salt water, circulating salt water through them, running at maximum rpm's with a load never felt when used in their automotive application.
Also, their location doesn't make them easily serviceable. That oil leak you see on your driveway won't be seen in the bottom of the bilge.
Diesels wont suffer as much as rpm's are limited and all that torque to get the boat moving is available at lower rpm's.
Metallurgy of the newer design outboards is superior to their inboard counterparts. Also most all have overhead cams, fuel injection, knock sensors, and run at almost half the rpms compared to their motorcycle cousins...
With the advent of 4 strokes, the makers were able to improve on an already proven design...
Couple of items that make a difference regular maintenance and how you run them.....if you cruise arond the 3500-4200 mark, they're gonna last alot longer, especially if they are propped correctly....regular maintenance is the key.....I'd say 1500-2000 hours for a boat used 200-300 hours a year would be about right....the average user who runs 100 hours per year, will normally lose it to corrosion before wearing one out....that being said, someone who runs 500 hours per year or more I could easily see getting 2000-3000 hours....there can always be that one special one that blows up...but that's with all engines.
But, is there anything different about the design/technology of an outboard 4s- as compared to an inboard- that backs up the claim? Typically, and inboard with over 1,000 hours (particularly if run hard) is regarded as being nearing time for a rebuild.
Most inboards are reworks of automotive designed engines not designed to sustain higher RPMs for long periods of time. Most 4 stoke outboards (with the exception of Honda) were designed for their intended marine application where high RPMs are normal.
Look at it this way, a Chevy truck with a 5.0L that has 100,000 miles on it would be in the autumn stages of it's life. It can however, with good maintenance quite possibly make it to 200,000 or more. The average vehicle speed for someone that drives both city and highway miles is around 25mph. That means for the truck to have 100,000 miles, it would have 4000 hours of running time. Even if it was "all highway miles" at an average speed of 50mph, it would still have 2000 hours on it. This is at least 2-4 times better (even using a conservative 100,000 mile life expectancy) than the 1000 hours for marine applications. This seems like fairly conclusive evidence that it was not designed for continued high rpm use.
It's a little harder to compare outboards this way, but we'll use the Honda since it is the only platform based on a automotive conversion. We all know that a Honda car with 100,000 miles has a lot more life in it. We also know that a small displacement 4 of 6 cylinder engine will have a higher final drive ratio than the aforementioned Chevy truck. This means that the Honda will be running at consistently higher RPMs. While you could argue the point, I think most of us will agree that a Honda passenger car with a 6 cylinder will outlast a Chevy truck with a 5.0L. To sum it up, a smaller displacement, higher reeving engine can (and will) outlast a larger engine if it is designed for the intended application. While this might not be a scientific example, it is certainly one that most people will understand and agree with.
I have a friend with a marine taxi service with over 13,000 hours on a set of 130 hondas. Most of the time is spent at lower rpms other than docking though since the operation is in a no wake zone.
4 strokes - engine hours? 
