Offshoreonly.com - What is Considered High Hours on an Engine?

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Quote:

Originally Posted by Ghost24 (Post 4478557)

Couple thoughts. With such a high percentage at 800-2000, I'd bet over 99% of that 97% was at idle or no wake speed, not at the lugging RPM where you're in the middle of climbing out of the hole. There are a few idiots who plow around like that but this sounds like trolling, so very little load. Aside from maybe running rich and fouling plugs so they need replacing, is there anything else about running at idle which lessens life more than duty-cycle use? HAS to be lower stress at idle on most components, no?

Running rich will wash down cylinders wearing them out.

That is not many hours for that motor and will last a lot longer than that before it needs to be tore down.

Quote:

Originally Posted by Wildman_grafix (Post 4478666)

Running rich will wash down cylinders wearing them out.

Thanks. Is that substantially more likely to happen with carbed motors than with EFI? I'd expect fuel injection might have a better shot at keeping the mixture right at very low RPM.

Quote:

Originally Posted by Ghost24 (Post 4478770)

Thanks. Is that substantially more likely to happen with carbed motors than with EFI? I'd expect fuel injection might have a better shot at keeping the mixture right at very low RPM.

Possibly yes, possibly no. A compression and leak down test will show if the rings are sealing. I would take an engine that passed both tests with low running rpm on the clock over an engine with higher recorded rpm hours.

Quote:

Originally Posted by jeff32 (Post 4478268)

1230 hours on my still sealed original 500 efi!!! No top end job done yet either!

I am jealous, just stuck a valve on one of my 525efi's with 346 hours. Looks like header failure tho. Was hoping to make 400 before top end service. NOT!

Quote:

Originally Posted by BUP (Post 4477833)

Depends how well its all been maintained from day one. Customers boats that I have maintained with 1200 hours in better condition and running conditions than new customers boats with 50 hours on it.

97 % of hours at 800 to 2000 rpms is not were an engine should spend its time to help with motor longevity. Actually that is like lugging and trolling the engine all the time.. Kind of like sitting idling your car 97 % time. Not going to last. Most marine engine run rich at very low rpm's and 2000 rpms is lugging a marine engine. That's like running your car up a steep hill all day in 5 the gear lugging the hell out of it.

You want marine engine that has ran most of its time at 70 to 75 % of its duty cycle.

Just an Example MAX - WOT 6000 RPM's - a good place to see rpms at would be 4000 to 4500 most of its run times.

I can't believe I am saying this, but I respectfully disagree with BUP. Yes, IF an engine was run a lot near 2000 rpms and plowing through the water, then yes you are lugging the hell out if it. But, I don't see people doing that(well, once in a great while). Stock MPI marine engines may run a little rich at idle, but they're not washing down rings. So, I don't think a lot of hours in the 800-2000 rpms is a bad thing.

Now, if you hopped in the boat for a test ride and the owner was one of those people that did "plow around" at just under 2000 rpms, then I would agree. But again, I rarely see people doing that.

How about twin Mercruiser 496's with 900 hours in a 37 Formula? New motors soon? Would you buy it? Of course broker thinks it's no big deal.

Quote:

Originally Posted by onesickpantera (Post 4478812)

But again, I rarely see people doing that.

Performance boats here,no.

Family boats,all the friggin time. Suks !

Ok not trying to play bad cop here but lets set the record straight

1. these are not 4 stroke motors

2 they are Optimax engines that depend on correct fuel pressure and air pressure from air injectors. One of the most important things for an opti to run.

3 Optimax's hate to troll around at low idle speeds for long periods all the time. they are plug foulers for long PERIODS of idle speeds. That alone washes down the cyc walls and or causes a lot of carbon build up.

4. The OP posted that 97 % of the run times were 2000 rpms and below --- IS THAT CORRECT ? Go ask any Opti expert that has torn these down and rebuilds them all the time. This thing could be very well carboned up like a pig. Also running an engine at one rpm always and or low rpms always does not promote good ring seal against the cyc walls.

5. How many has even worked or even changed spark plugs on a Opti up here ? If so you will and can tell some of the driving habits , trolling and low idle most of the time will be carbon / plug fouling all over the spark plugs. Not uncommon at all.

With any marine engine runs times is another way to look at when buying an boat / engine. Again look for run times 70 to 75 % of max load more so than an engine that has higher idle rpms and WOT. Of course maintenance is a huge part of it. Proper Cooling and fuel / ie rich and lean running as well important.

Quote:

Originally Posted by SB (Post 4478825)

Performance boats here,no.

Family boats,all the friggin time. Suks !

Not around here. I do believe you get your azz kicked for that! :)