Marine Gas Engines, Life Expectancy

I saw a number of references to gas engine life expectancy in this article....
Marine Engines : Gas Engines - by David Pascoe, Marine Surveyor

...but what surprised me is nothing about 'engine hours' of life??

I know that many marine engines are equipped with 'hour meters', and certainly there sure be some approximates as to engine life in man-hours.

How about it, any folks want to contribute their figures to that subject?? I've been told to avoid anything with over 1500 hours on it as likely they all requires rebuilding or replacement as they approach 1800-2000 hours. ??

 

Crusader 454 and Merc 454

That previous post was to consider most specifically these two big gas engines that are used to power a lot of larger motoryachts 35' plus....

 

I suppose there is a good deal of variability in how those engine hours are accumulated, a boat that was used for sportsfishing and spent a lot of time trolling might have had a much easier life than something being flogged along at high revs every hour it ran. Either way, 1500 hours would take quite a few years to arrive at for the general run of recreational boats, and age-related issues would play a part as well as running hours.

 

You will get closer to an accurate number if you use liters of gasoline burned. You also have to define "life".

I don't agree with Pascoe's views on engine "overload" or the "must run up to rated rpm" theory.

 

How to obtain that data ? Might be possible with up to date computerized engines. The number of cold starts would also be of interest, but only the lord above knows the answer ! I have heard of 4-stroke outboards doing 3000-4000 hours without a rebuild in commercial use such as water taxis, a bit like taxicabs doing 500,000 miles on petrol/gas without the head coming off, the engines were rarely cold.

 

I just changed a pair of 454s with over 5000 hours on them. They were on a charter boat so they wanted new to be sure. However, they were still running OK but using some oil. A private boater bought them and put them in his boat.

 

A 454 over 5000 hours would burn enough fuel $ to frighten most people severely.

 

What are these, as distinct from non-gender qualified hours ?

 

The big outboard motors seem to have a service life of 2000 hours and this limit is corrosion.

 

From personal experience (5 Mercruisers, 1 Volvo Penta, 1 OMC): engine hours do not matter.
It is the environment that kills a boat engine. Seawater eats through exhaust manifolds of directly cooled engines in less than 10 years. Water dripping on an engine can damage the thin timing chain cover, causing rapid loss of oil; it may also ruin an aluminum engine coupler or shorting the ignition.

Another important factor is poor maintenance. While car makers have a network of qualified dealers and well equipped workshops, the boat engines are often serviced by marina people who claim to be familiar with all types and brands.

 

I have a small gas engine, I've loving cared for since new and it currently has 6,400 hours on it. It needs a rebuild, but runs well using a fair bit of oil. It'll be a winter project this year. CDK is right, there's no real "hour window" to use as a gauge. It's about maintenance and neglect. My little motor received several upgrades very early in it's life, because I wanted a long life from it. Improved cooling (a big deal in the tropics), improved intake and exhaust for efficiency and cooling, Fuel delivery tweaks, maintenance easing modifications and a religious routine to keep it clean and fresh.

The only engines you can get reliable hour estimates are those that will receive continuous load and maintenance, so you can generate a base line and have something to compare to. For example a generator, that runs at 80% load, 90% of the hours it runs with a reasonable and routine maintenance schedule, is an easy thing to predict. You can almost pick the day it will toss a rod or eat a valve, so it's replacement is simple.

This isn't what you get with a typical pleasure craft. The range of care alone will be all over the place, as will maintenance, loading, abuse and neglect. On the other side of the coin, commercial craft do have reasonably good routines, scheduled parts replacement and can be expected to predict, fairly accurately when a power plant will crap the bed.

It all about the controls installed as an owner.

 

Im sure a gas engine can have a long life. My family had a straight six ford falcon. By the time the car fell apart due to rust it had 300,000 miles on it. The engine was ok, burned some oil and only ever received normal maintenance. .

Modern, high output gas engines might be a different story,

My friend replaces his big 4 stroke outboards that he uses for fast inter island ferry service, every three to four years because the repair cost is too high . Engine mounts, electric harnesss, lower unit, sea water cooler corrosion , hydraulic tilt...the engine itself seems Ok.

 

An automotive engine typically sees 20% load, 80% of the hours it operates. Marine and aircraft engines are typically the reverse of this, if not higher, so not a reasonable comparison.

 

Many of the modern diesels are auto engines where,
>An automotive engine typically sees 20% load, 80% of the hours it operates<
is the rule.

WOE to someone that installs one of these marinizations and believes the mfg HP ratings are like a big truck or commercial engine , and can be used 80% of the time.

 

I was told once a very rough guide to marine gas engine wear is 1 hour in a boat is equal to 100 hours in a car. This means at 1,000 hours the engine has 100,000 miles on it, which is pretty reasonable. With newer engines, tolerances are much better, so getting a gas marine engine to 3,000 hours isn't unusual.

Diesels are a different animal, being built much stouter for obvious necessities, though dedicated marine engines do seem to out live automotive marinazations.