Mercruiser Engine life

[Dr. David Fleming]

Anyone know what the expected operational engine life on the various Mercruiser V8 engines are? Ran across an article in the Boaters Pocket Reference:

"Diesels have achieved a reputation for operating 20,000 hours without major overhauls and this is often compared to a typical gasoline engine operating life of around 2000 hours."

I believe Tyler Crockett mentioned to me somewhere that the average Merc 502/454 had a useful operating life of about 400 hours.

I do about 80 hours per summer - about 5 years for me - or 25 years - depending on which reference - anyone run a big Merc till it dropped?

[mrfixxall]

Anyone know what the expected operational engine life on the various Mercruiser V8 engines are? Ran across an article in the Boaters Pocket Reference:

"Diesels have achieved a reputation for operating 20,000 hours without major overhauls and this is often compared to a typical gasoline engine operating life of around 2000 hours."

I believe Tyler Crockett mentioned to me somewhere that the average Merc 502/454 had a useful operating life of about 400 hours.

I do about 80 hours per summer - about 5 years for me - or 25 years - depending on which reference - anyone run a big Merc till it dropped?

my friends 89 454 mag has over 1200 hr's on it.. it all depends on how you take care of them..

[BUIZILLA]

I know of a couple tow boat owners that have over 3,000 hours on 454's... 800 hours is really only 25,000 miles in car talk, if that.. it all depends on the HP level and routine RPM usage.. a boat engine cruising at 4000 rpm has 1/4 the life of a car engine at 2000 rpm, mainly due to engine load

20,000 hours on a high speed diesel is a wet dream... your lucky to get 2,500 out of a TA GM series.. but I have seen Luggers go well past 25,000 and a pair of 3512's that went past 35,000.. i've done 84 fuel/governor systems for the Coast Guard 3304 Gen Sets and their requirements are 15,000 hours mandatory between services, so far we are at 100% success.

[Carl C]

So what should be done to a performance engine after, say, 1,000 hours of somewhat hard operation? Bore .030 and fit new pistons? Grind crank .010? replace valve springs and valves? What should be done to prevent catastrophic failure and when?

[The Hedgehog]

What Buiz says on Diesels. I would be thrilled to get 2,500 on my DD's. I know of many that run into 4-5-k with N/A's. The 5k guys....I don't know much about but they claim it. Gens are a little different. My diesel guy says I can get 5K on my gens if I run them and 3k if I don't. I run them and so did the prior owner. The new Gens get much more.

Around here we figure 500 hours for a 502 mag. You will probably have to bore it past 400hrs. The 496 should be the same.

People get the 800 hour mark on I/O cruisers that are properly maintained. That is not far from Fix's number.

I had 1,000 on my 454 Crusaders in the Marinette. They probably had another 500 to 1,000 hours. I ran them mostly at 2,000 rpm. so did the prior owner.

On the rest, it depends on boost. Eddie has a set of 950's that are cracking the 300 hour mark. That is not usual. 250 is a number for those.

N/A vs Blown engines is always a discussion. Big power N/A's have huge cams and beat up the heads pretty bad. Big boost = high cyl pressures and wears on the rest.

I will tear into the 850 at 200 hours to do the heads.

[The Hedgehog]

So what should be done to a performance engine after, say, 1,000 hours of somewhat hard operation? Bore .030 and fit new pistons? Grind crank .010? replace valve springs and valves? What should be done to prevent catastrophic failure and when?

You won't make 1,000 hours of hard operations. Heads will need to be done every 200 and it will need to be bored at 400-500.

[mrfixxall]

So what should be done to a performance engine after, say, 1,000 hours of somewhat hard operation? Bore .030 and fit new pistons? Grind crank .010? replace valve springs and valves? What should be done to prevent catastrophic failure and when?

no offence carl, i see the way you run your boat.. with that being said i would think about replacing your valve springs @ 250 hr's..if you want to get more life out of them then do what i do..get 16 Allen set screws and install them in your poly locks on the rocker arms(double set screw them) and after each season loosen the poly locks on your rockers that have spring tension on them..some old races told me to do this back in the 80's and i have been doing this to all my engines that sit ever since..never had any valve spring problems..

[gcarter]

What about a really large inch engine, maybe 600+ cu. in., and set it up for 500-550 HP @ only 4000-4500 RPM.........
Couldn't you expect a bit more longevity out of it, assuming you did most of your cruising @ 2500-3000 RPM???

[Rodger]

if you want to get more life out of them then do what i do..get 16 Allen set screws and install them in your poly locks on the rocker arms(double set screw them) and after each season loosen the poly locks on your rockers that have spring tension on them..that sit ever since..never had any valve spring problems..

I have also been doing this for the last 20 years.

[Pismo]

I got 3000 hours out of a 305 chevy mercruiser 228 fresh water without getting into it. Still ran great, small, light boat, under 3000 rpm 95% of the time. Lots of new accessories, starter, alternator, etc but the internals were all original. Definitely lost power over the years but still ran great, good compression, original pre alpha R drive. Lots of valve train noise on first startup of spring but that quieted down quickly.

If I had run it harder in a heavy boat it would not have lasted 1/4 as long.

Hoping to get 750-1000 hrs out of my current fresh water 502 in a 22 which I run under 3000rpm 99% of the time. Only at 300 now and all seems good still.

[Carl C]

no offence carl, i see the way you run your boat.. with that being said i would think about replacing your valve springs @ 250 hr's..if you want to get more life out of them then do what i do..get 16 Allen set screws and install them in your poly locks on the rocker arms(double set screw them) and after each season loosen the poly locks on your rockers that have spring tension on them..some old races told me to do this back in the 80's and i have been doing this to all my engines that sit ever since..never had any valve spring problems..

I often cruise at 4,000 rpms with bursts over 5,000. Not always of course but when conditions permit running hard. I don't back off the rockers but turn the engine over manually a little several times each winter so no springs stay fully compressed for long. The engine is only down 5-6 months each year and stored indoors. So the heads need to be rebuilt often. I suppose the engine will let me know when it needs boring when the compression starts dropping? I change the oil 3 times each season now.

When the heads are done should the valves be replaced with new ones because of possible fatigue or is it Ok to do a conventional high performance 3 angle valve job and replace the springs?

[mrfixxall]

I often cruise at 4,000 rpms with bursts over 5,000. Not always of course but when conditions permit running hard. I don't back off the rockers but turn the engine over manually a little several times each winter so no springs stay fully compressed for long. The engine is only down 5-6 months each year and stored indoors. So the heads need to be rebuilt often. I suppose the engine will let me know when it needs boring when the compression starts dropping? I change the oil 3 times each season now.

When the heads are done should the valves be replaced with new ones because of possible fatigue or is it Ok to do a conventional high performance 3 angle valve job and replace the springs?

merc uses good valves on that engine,,all you really need to do around 300 hr's is the valve springs and possibly the lifters..But still do a compression test and a valve leak down test, if it passes then just do the springs..if you have a boar scope while doing the springs have a look at the sides of the lifters @ full lift and look for any chaffing on the side of the lifters,if present then replace them because it will only ware the lifter boars out..

[Carl C]

merc uses good valves on that engine,,all you really need to do around 300 hr's is the valve springs and possibly the lifters..But still do a compression test and a valve leak down test, if it passes then just do the springs..if you have a boar scope while doing the springs have a look at the sides of the lifters @ full lift and look for any chaffing on the side of the lifters,if present then replace them because it will only ware the lifter boars out..

OK, thanks.

[DonZi 26]

i'd say it all depends on the way one treats the engine....treat it right and it will treat you right! hit it hard and she will hit your pocket hard, trust me....i've a 1993 merc 502 dont know the exact hours on it but id say it probabbly has about 1500hrs....it runs flawless, only replaced rings and bearings once about 5yrs ago(my choice not coz they needed to be replaced) ...

another major issue with engines is the stock riser exhaust ! by time the riser tends to rust and water may leak onto the piston causing seizure, so the life span may be affected by this matter...in my case i've always ran my engines with dry exhaust....thats a rule of thumb for me ! i just dont trust the stock manifolds they re not trust worthy....but all in all a well maintained engine should survive around 1500-2000hrs

[oledawg]

Since I am the 3rd owner of my '88 22C I have absolutely no idea how many hours or how it was run. All that I know is that when I fire that bad boy up all sounds fine....a little white puff of smoke at ignition.....no strange noises at all ( that I can hear with the engine hatch open ). Run at idle in the slip until it warms up, most cruising at 3500 with a few runs at WOT ( 4,800 rpm with the current setup ). Gets run alot during 6 months of the year, two oil changes during that time, but from late October until early March it just hangs in the boathouse. So, my point.....when it breaks I will fix it