Marine (ized) engine horsepower loss over time

[Red Tide]

OK, time for my overly broad question of the day today:

I'm wondering how many horsepower is a normal gas sterndrive engine expected to lose as the hourmeter ticks by...

Let's say a carb engine sportboat used 100 hours a year on weekends. The owners are a typical family who have the boat serviced once or twice a year by a marina mechanic.

If the engine starts life at 300 hp when brand new, what would you expect this average mercruiser or volvo gas "car" engine to have for horsepower after 5 years and 500 hours of running in typical recreational use?

[FAST FRED]

"If the engine starts life at 300 hp when brand new, what would you expect this average mercruiser or volvo gas "car" engine to have for horsepower after 5 years and 500 hours of running in typical recreational use?"


YES , the reason is the car engine RATED at 300 hp will last an hour or two at that rating , BUT operated normally at 150hp (15gph) or at times 200hp (20gph) the service life will be almost 2,000 hours if maintained and not abused.
The bit of full throttle dragging a cruiser up on the plane is no problem (10-15 seconds) IF the engine is at operating temp.

Will there be some power loss from leaky valves , ignition not spot on , or crud in the fuel , OF COURSE , but with the % throttle used at std cruise , a tiny bit more wont be noticed.

FF

[BHOFM]

A new engine will improve for the first 1/3 of its life, then hold for 1/3 then
start a slow decline over the last 1/3.

Two stroke engines improve for about 1/2 of their life, decline quickly.

This is for engines that operate in normal conditions with proper care.

The air filter is the key to engine life.

[CDK]

Look at GM's industrial engine site to see how the particular engine is rated. It will be much lower than 300 hp of course because the industry is not interested in fiction but in facts. At the given rating the engine has a substantial service life and even at the end, when the oil consumption tells the owner it is time for something new, the power output hasn't changed noticeably.

The Mercruiser rating is something totally different.
It means "we want you to believe that this engine could deliver 300 hp, but it doesn't, it just sounds good and you probably wouldn't have bought it if we told you the truth".
500 Hours and 5 years later, nothing has changed.

[Red Tide]

The air filter is the key to engine life.
As opposed to a flame arrestor alone?

[Red Tide]

Look at GM's industrial engine site to see how the particular engine is rated. It will be much lower than 300 hp of course because the industry is not interested in fiction but in facts. At the given rating the engine has a substantial service life and even at the end, when the oil consumption tells the owner it is time for something new, the power output hasn't changed noticeably.

The Mercruiser rating is something totally different.
It means "we want you to believe that this engine could deliver 300 hp, but it doesn't, it just sounds good and you probably wouldn't have bought it if we told you the truth".
500 Hours and 5 years later, nothing has changed.
Glad to hear the longevity of "car" engines professionally adapted for marine use is a lot better than I had feared. Looking at the GM website, they rate their OEM vortec marine at 292 hp
http://www.gm.com/experience/technology/gmpowertrain/engines/specialized/marine/2010_5700_Marine.pdf
while the block for industrial use on different fuel is rated at 216 hp
http://www.gm.com/experience/technology/gmpowertrain/engines/specialized/industrial/2010_5700_Industrial.pdf
which I suppose is continuous, but the different fuel confuses me when making a comparison...

[TollyWally]

"we want you to believe that this engine could deliver 300 hp, but it doesn't, it just sounds good and you probably wouldn't have bought it if we told you the truth".

LOL, that's a fact. I have a gas motor rated at 330 hp. The real motorhead guys at a dragboat site I sometimes frequent have told me it might top out at 280 on a real good day. With the carb adjusted the way it is now I am topping out at 220 or so.

[apex1]

As opposed to a flame arrestor alone?

There is no air filter on a marine engine! Just the flame arrestor.

[broke_not]

Look at GM's industrial engine site to see how the particular engine is rated. It will be much lower than 300 hp of course because the industry is not interested in fiction but in facts.

Industrial engines are always rated lower, but it isn't necessarily because there's anything "fictional" about the non-industrial engine ratings. The big difference in the hp numbers is there because the industrial version typically has its hp "rating" taken at around 4000 rpm. That doesn't mean it isn't capable of producing more hp, it simply means that the equipment it's marketed towards, (genset/pump/whatever), requires a power spec at a given rpm that will give a reasonable service life.

It would be silly to rate non-industrial engines the same way. If a car or light truck engine is designed and built to be able to produce, say 275 peak hp at say, 5000 rpm.....what would be the point of "rating" it at 4000 rpm? Alternatively, what would be the point of listing a peak hp rating achieved at 5000 rpm for an industrial engine that would never see 5000 rpm?

A peak hp rating doesn't mean it's fictional.



;-)

[Frosty]

Max Hp is different from the Marine rated because the marine rated is constant.

Constant output is the Hp that it is designed to give for hours -days on end.

Something a marine engine is often required to do, rather than a minute at a time whist changing gears in a truck.


Marine Engines don't have filters?? Do you mean need or have?

[Red Tide]

The question of air filters is one I have not considered -- now that you mention it I think I've seen what looks like air filters on larger gas EFI engines. On my gas carb engines I've only ever had the metal screen flame arrestors. What would get sucked through those screens to damage the engine? My bilge usually contains a little water, a tiny bit of grease, and maybe a tiny tiny amount of sand/debris carried by shoes or from the cockpit when working on the engines, but I don't think that would be sucked up. Maybe around the beach around sanddunes there would be hard particles in the air? I'm curious what the air filters do on a boat if people are using them...

--A swarm of tiny gnats?

[CDK]

This discussion has come up several times already.
What Mercruiser sells as a marine engine is an old-fashioned GM block painted black. The materials used and the half a century old design make it unsuitable for the advertised output power if longevity is required.
The engines did well in passenger cars when fuel efficiency was no consideration. Speed limits and the ever present automatic gearbox kept these engines from reaching more than 3000 rpm except for a few seconds. As industrial engines they still do very well because the low rpm seriously reduces the power output so a long service life is obtained.

The concept "marine engine" is too wide. A real marine engine is of course a diesel with 2 stage cooling, designed for or adapted to a long life propelling a boat. Such a performance cannot be expected from the gasoline engines this thread is about.
In a recreational GRP boat they are reasonably reliable because a year generally means one holiday plus a few weekends and the owner, once he is familiar with the fuel bills, pulls back the throttle to 3500 rpm or less. Again the actual power output is at or below the industrial rating.

A different situation develops when these engines are used for the propulsion of heavier vehicles like cabin cruisers that stay in the water most of the year. The weight/power ratio and marine growth forces these engines to do hard labour and premature engine failure is at the horizon.

[broke_not]

This discussion has come up several times already.
What Mercruiser sells as a marine engine is an old-fashioned GM block painted black. The materials used and the half a century old design make it unsuitable for the advertised output power if longevity is required.
The engines did well in passenger cars when fuel efficiency was no consideration. Speed limits and the ever present automatic gearbox kept these engines from reaching more than 3000 rpm except for a few seconds. As industrial engines they still do very well because the low rpm seriously reduces the power output so a long service life is obtained.


All well and good, but that still doesn't mean that there's anything "fictional" about the advertised power output.....which is what you said a few posts up.

The Mercruiser rating is something totally different.
It means "we want you to believe that this engine could deliver 300 hp, but it doesn't, it just sounds good and you probably wouldn't have bought it if we told you the truth".

There it is right there. "We want you to believe this engine could deliver 300 hp, but it doesn't...."

Sorry, but it does.

You can post up a couple of long, meandering paragraphs in response if you like, but unless you edit what you've already posted....it's going to come off as back-pedaling.

I'm just sayin'....

;-)

[CDK]

You must be a Brunswick shareholder. Sorry I offended you.

[broke_not]

Not offended, nor am I a Brunswick shareholder. (Although I do find the "Brunswick shareholder" comment a little offensive. Does someone not sharing your opinions automatically mean they have some monetary motivation?) You made a couple of statements that were delivered in a pretty matter-of-fact manner. But they were just opinions.....and that's all.

Remember this thread?

http://www.boatdesign.net/forums/gas-engines/carb-fuel-injection-conversion-22495.html

You did the same thing there. You started out with a matter-of-fact statement about fuel pump motors being brushless, but again....it was opinion more than fact. And rather than 'fessing up about the comment being more opinion than fact when some evidence to the contrary was presented, well....read the thread.

I'm just sayin'....

Long story short, if an engine manufacturer gives one engine a peak hp rating, and then gives the industrial version of the engine a hp rating at a lower rpm around where its intended use will be.....there's nothing fictional about either rating.

;-)

[Frosty]

Mercruiser engines used to be Chevrolet before they were Ford, a lot less than half a century ago.

[CDK]

You are partly right and partly wrong.
I believe the purpose of forums like this is that people can give their opinions. You cannot expect me to give someone else's opinion. That I present mine in a matter-of-fact manner seems to bother you, but maybe I see facts where others do not.

Over the years I also have been a customer of this Jukebox/Bowling alley company. I've had 6 Mercruiser engines and 4 Mercury outboards. In fact I still use a 5 hp that serves me very well. Future buyers I advise to buy one from Tohatsu: the price is much lower and you get the same product, but in dark gray instead of black. Fact or opinion? You figure it out.

But back to the topic.
From personal experience, albeit long ago: I bought a brand new boat with a Merc V-8, 12 months warranty, service done by Mercruiser approved people. After 13 months and approx. 60 engine hours (that's normal for pleasure craft, they do not expect you to really use it), the engine went up in smoke. One piston traveling free, one head cracked and the camshaft severed in two almost equal pieces. Warranty claim refused, but the insurance did pay (almost) everything and I got a new, even more powerful (?) engine that also had a violent death, but not during my ownership.

There are numerous examples to show that commercial companies claim unrealistic performance, because the truth would substantially drop their sales. But in the industrial field things are quite different: you don't get away with such behavior. That is why I have more faith in industrial ratings.

About the fuel pump.
I never provided the link you asked me for; bad habit maybe, but I rarely ever do that. The brushless Japanese pump I took apart and reassembled is submerged in a large fuel tank filled when the price was right, so I can't even show you a picture....

[broke_not]

You are partly right and partly wrong.
I believe the purpose of forums like this is that people can give their opinions. You cannot expect me to give someone else's opinion. That I present mine in a matter-of-fact manner seems to bother you, but maybe I see facts where others do not.


"Maybe I see facts where others do not."

Seriously, were you giggling as you typed that? Forums are chock-full of opinions, but problems can arise when people go to those forums to get information....and the information turns out to be inaccurate. The simplest solution, is when you offer up something that's your opinion, identify it as such.

"It's my opinion that <insert opinion here>"

Don't start out with a matter-of-fact declaration.

Then when someone opposes or challenges your opinion, don't shovel on a bunch of *bs*. That's where the "baffle them with bs" phrase came from.

In closing, I'd once again like to point to your "Brunswick shareholder" comment. It speaks more clearly about your methods than I ever could.

Cheers.

[apex1]

Then when someone opposes or challenges your opinion, don't shovel on a bunch of *bs*.

Hmm, you should make that your motto too!

Of course CDK was right, these old iron pigs live for minutes only, when they have to crank out the hp they are advertised to deliver. That IS fiction.

And talking BS is, when one tells us industrial engines are set at 4000 rpm. That is the sheer nonsense. There are so many different applications, that you can find the same engine with settings from 1500 to 5000 rpm easily. In marine setup the cont. output is the one that counts, as mentioned above.

[broke_not]

They'll last for "minutes only" when cranking out their advertised hp?

Really?

And even if they did, at what point does that advertised hp number become "fictional"?

FWIW, I never said industrial engines were "set" to 4000 rpm, I said they have their hp "rated" at a lower rpm. Manufacturers of industrial equipment need to know when choosing a powerplant what it's output will be closer to the rpm range it will see in the use they have in mind for it. Like I posted earlier, it really makes no sense to advertise, (by the engine manufacturer), what an industrial engine's "peak" hp rating is.....because in the applications it will end up in, it won't be seeing that rpm ever anyway. I happen to maintain a fleet of such industrial equipment, and the equipment manufacturers don't give a hoot what a 3.0 GM four, (or whatever the case may be), will produce for a peak number. They're concerned about the power level at the rpm it will see in normal operation. If the directly-coupled hydrostatic pump for instance is designed to be most efficient at 3000 rpm, they'll choose an engine that produces the hp desired at that engine speed. In a genset, if the directly-coupled generator head needs to spin at 1800 or 3600 rpm to operate correctly, then the genset manufacturer will look to the engine supplier for an engine that produces the required amount of power at that rpm.

In non-industrial applications in which the rpm range varies as widely as it does, a peak number is more relevant.....because it's what everyone uses. Imagine all of the confusion there would be if it were done otherwise. You can't market your product against the competitor if you're rating your products differently. As a customer, you can't comparison shop if the products are rated differently.

Simply put, there's nothing "fictional" about the ratings of industrial or non-industrial engines. They're rated differently, for good reason. It doesn't make either rating "fictional".

And talking BS is, when one tells us industrial engines are set at 4000 rpm. That is the sheer nonsense. There are so many different applications, that you can find the same engine with settings from 1500 to 5000 rpm easily

Please provide some of these easy-to-find examples of industrial engines with 5000 rpm "settings". And by "settings", I mean an application in which an equipment manufacturer designed their machinery in such a manner that they had to send their engine supplier a spec for an engine that would be turning at 5000 rpm all day long. That certainly seems to directly oppose your earlier statement about engines only being able to live for a few minutes under those conditions...


;-)

[CDK]

In closing, I'd once again like to point to your "Brunswick shareholder" comment. It speaks more clearly about your methods than I ever could.

Cheers.

It seems I struck a nerve there.
But honestly, that could in my opinion be the only sound reason for defending the merits of these engines. Although since my retirement I cannot afford a Mercedes ML anymore, I helped out Daimler-Benz with a considerable sum. Solid people, never caught them telling lies, so of course I would defend them.

Look at Mercruiser 2009 on the web: they offer the patented TKS technology for a variety of hopelessly outdated fuel wasting carb engines that were banned by legislation for road use years ago. TKS means Turn the Key to Start: a truly great invention, why didn't I think of it. Much easier than saying all these prayers most boat-owners need to wake up their horses.

Ask them for a torque/power curve (you won't find any on their websites) and they will reply that it is proprietary information and company policy not to disclose such information. I know for sure because I did ask. It is like asking the guy with the longest dick on the block to pull his pants down. If you have nothing to hide, like Cummins, Steyr or VW, what reason for secrecy could there be? Confusion for sure.

To some, doing business means buying as cheap as possible and selling to ignorant customers at the maximum price, all tricks allowed. We live in a world of tricksters and conman going at great length to make us part from our money. Your car stereo cannot produce 500 watts while drawing only 4 Amps, your 1000 watt speakers start smoking at 10% of that power and your laptop doesn't clock a 4 Ghz or even 10% of that. Compared to that, the Merc 250 doesn't do so badly during the first few hours.

[broke_not]

Your car stereo cannot produce 500 watts while drawing only 4 Amps, your 1000 watt speakers start smoking at 10% of that power and your laptop doesn't clock a 4 Ghz or even 10% of that.Okay, so then when an engine manufacturer provides a dyno chart for an engine that clearly shows what the produced amount of power is, then how is the provided number "fictional"? Your examples may very well be exaggerated specs designed to fool consumers, but then again, when they exaggerate, they aren't providing any proof about where those numbers came from....are they?

It seems I struck a nerve there.
But honestly, that could in my opinion be the only sound reason for defending the merits of these engines. Although since my retirement I cannot afford a Mercedes ML anymore, I helped out Daimler-Benz with a considerable sum. Solid people, never caught them telling lies, so of course I would defend them.
Can't fault you for "defending them", but it is a little ridiculous to then assume that anyone with anything to say that doesn't agree with what you happen to believe must have some "motive" other than wanting to clear the air and provide some accurate information.

;-)

[Red Tide]

Okay, so then when an engine manufacturer provides a dyno chart for an engine that clearly shows what the produced amount of power is, then how is the provided number "fictional"?
In the great majority of installations as rigged will the engine survive as "advertised"? If not, it seems fictional to me. If so, then ok understanding the rating is for occasional use. What I mean is what happens if a typical boat owner runs the engine at 4,000, 4,500, or 5,000 RPM for 30 minutes once a week (while cruising the majority of the time at 3,000 RPM or about 1/2 output) What will a little bit of running at the engine's higher horsepower RPM range or running a little bit at WOT do to the average mercruiser gas engine?

[Frosty]

Ive blown more American iron than any other engines. Be it cars or boats.

[Red Tide]

I suppose you have to look at the warranty as the boundary of fact and chance... 1 to 3 years is what they're warrantied for. Beyond that... (scary if you take the engine cost and divide it by the 1 to 3 years of use)

[tuantom]

Used to have a Ford 351w in my dad's boat that my brother and I'd beat up pretty regularly back before I knew how to pay for things. Was rated at 250 HP and we'd try to use all that as often as possible - WOT @ ~4300 rpms for 15 or 20 miles was common enough (Gas was cheap in the 90's). It never blew up - though it was mighty tired after about 18 seasons. My brother's been keeping that up with his own boat with a Mercruiser 260 for the last 7 or 8 years now - though it's been tempered a bit by higher gas prices.

I've personally seen many examples of small block and especially big block engines being a lot more durable than being said here - Comparable to a Mercedes? I'd guess probably not; but I probably could build 5 of them for the cost of one Mercedes.

[powerabout]

i have seen a 260, 330, 370 Mercruisers with dry headers on a dyno and they made
260 330 and 370 FTLbs of torque and hence the horsepower numbers were less.
Maybe we read the numbers backwards downunder.....?

I do know the above info led to a court case (in OZ )with a boat builder when he found out a 260 isnt 260hp.
(Nothing to do with the project I was involved with but the dyno shop supplied the info)
It was settled but I never found out and Merc wouldnt say?

On the old K&O hydraulic dyno's a 260 Mercruiser and the old 225 merc outboard pumped nearly the same pressure?

[Yellowjacket]

Most if not all reciprocating engines, be it gas or diesel cannot operate at wide open throttle for any extended period of time.

If you go to the MAN website and look at the ratings, typically they rate the engine at a given power, but then in the fine print say that it is only supposed to be used for no more than 1,000 hrs per year and only for 20% of the time at full power and the rest of the time it is assumed to be used at 50% power. The warranty for the engine is 24 months. If you take it to mean that the engine might last for about 400 hours at full power you are probably pretty much on the money.

I am not picking on MAN, they are simply typical and I had data on their engines. I am sure that they make a good engine, but ALL reciprocating engines have their limitations. They can all put out more power for short periods of time than they can for a long time. When you select your engine you simply have to figure how YOU are going to use it and decide on a power rating that is appropriate for YOUR application. If you need more power you can't run the weee weee out of an engine and expect it to live.

I have disassembled an aircraft engine that had 2,300 hours on it at 75% and greater power and everything in the engine was just plum worn out. Marine engines are like aircraft engines in that they can be run at high power levels for extended periods of time, and that is simply severe service. You can't expect an auto engine that can make 350 hp at 6,000 rpm in a car to live long if you lock down the throttle in a boat. Nobody is lying about the ratings, the engines make the power they advertise, but you can't run ANY of them at that power and expect them to live a long time.

Keep the amount of time at max rated power down to below 20% (a typical "pleasure craft" rating) and they will last a long time. But if you underpower your boat and bend the throttle over and expect the engine to live very long you are kidding yourself.

[CDK]

I have disassembled an aircraft engine that had 2,300 hours on it at 75% and greater power and everything in the engine was just plum worn out. Marine engines are like aircraft engines in that they can be run at high power levels for extended periods of time, and that is simply severe service.

That is very interesting.
Aircraft engines are not the topic here, but now that you mentioned it, they are very conservatively rated for obvious safety reasons. Extremely well built from superb materials, they should last much longer than 2300 hours.
Could it be that the one you took apart was used for other purposes? Normally an aircraft engine is disassembled, inspected and reinstalled quite frequently to obtain certification for the next 12 months.

I remember that jet engines at run-up were allowed to rev up to 110% power, sometimes even more.

[Yellowjacket]

Most normally aspirated reciprocating aircraft engines have an FAA rated Time Between Overhauls of about 2,000 hours. You can look it up on the type certificate data sheets that are on the FAA web site. At that point they are pretty much ready for an overhaul. Typically the valves and valve seats are showing wear, the pistion rings and bores are worn and there is a lot of burned oil in the ring grooves. All of this is a function of time at temperature and load. Generally the feeling is that if you run much past TBO you are asking for trouble. Very seldom do general aviation engines such as a Lycoming or Continental run much past TBO, and many never make it that far. Most are run at 75% power with higher power settings for a few minutes (like five or less) at takeoff power. If you loaf around you might go further, but that is about the typical life expectancy between rebuilds.

Turbines are another matter entirely. Depending on how the turbine was rated, there may or may not be the capability to run the engine at higher power for short periods. The life of uncooled hot section components typically degrades by half for each 25 degrees F hotter that you run it. That is, run it 25 degrees hotter and the life is reduced to half of what it was at the rated temperature, run it 50 degrees hotter and the life is 1/4. The opposite is also true, if you run it 25 degrees F cooler, the life will double, 50 degrees cooler and the life is 4 times longer and run it 100 degrees cooler and the life is 16x greater. Typically a slight derate of 50 to 75 degrees for use in a boat or in ground power applications results in a turbine that will last pretty much forever.

Ratings of takeoff power in aircraft turbines are very different than turbines used on the ground. Often there are limits that are applied to a turbine in the takeoff mode to limt the power in the fan or gearbox. In many cases the engine is running harder at cruise due to altitude effects, than it does on the ground or at takeoff, consequently, there is no real comparison with reciprocrating engines other than if you run it too hot for too long the life goes into the toilet.

[powerabout]

That is very interesting.
Aircraft engines are not the topic here, but now that you mentioned it, they are very conservatively rated for obvious safety reasons. Extremely well built from superb materials, they should last much longer than 2300 hours.
Could it be that the one you took apart was used for other purposes? Normally an aircraft engine is disassembled, inspected and reinstalled quite frequently to obtain certification for the next 12 months.

I remember that jet engines at run-up were allowed to rev up to 110% power, sometimes even more.
And stoneage a 1949 cessna is basically the same as a 2009
carburettors and magnetos??
The industry is happy where it is no new entrants therefore no need to change and no EPA to go and change that

[thudpucker]

I don't think air-cleaners mean a thing to the gas engine.
But to the Carb they sure do. I've seen the Venturi almost gouged out on engines that spent their lives with the same Air filter.

Almost every carb that's been on a Marine engine operating in Salt water, inhaling salt Crystals, has a worn out venturi also.
Thats where a lot of the loss of HP comes from in a Gas engine.
A Venturi made of Carbide Steel would probably maintain its HP much longer than the Pot metal carbs would.

Diesels are not bothered with little things like Breathing salt air.

Having had the experience of rescuing an engine that was over heated repeatedly, I noticed the loss of HP. It started and ran OK, just soft on acceleration at working Rpm's.
The Rings were cooked. They just wouldn't seal good at the higher Rpm's.

I believe the extreme hi torque load on a Marine engine, all its life, does about the same thing to the Rings. They just don't seal as well once they've been cooked. All that load, all the time, is the same as cooking.

Why Diesels don't suffer the same fate probably has something to do with oily cylinders. Just a guess there!