Outboard longevity vs. Car motor

[thatone123]

I was wondering why outboards seem to have so many engine problems compared to car engines. They both mostly 4 stroke today have pistons cylinders and are water cooled. Seems outboards develop all kinds of cylinder problems etc. even in fresh water. 2 strokes seem to last longer and develop less problems than 4 strokes. Some have said that 2 stroke outboards develop less harmonic vibrations than 4 just simply going up and down and no valves to create vibrations. 4 stroke outboards are heavier than 2 stroke outboards but still vibrate as they are not attached to a heavy frame like a car or truck so do not last as long??? So an outboard diesel maybe would not last as long as a truck diesel for the same reason as the outboard diesel could not be as heavy. Just food for thought!

 

[jimmbo]

If you drove you car engine at full throttle continuously, did not reuse the coolant, operated it at much lower temps, it too would have more problems and a much shorter life span.
Lack of maintenance is probably the biggest reason for poor performance and contributes to shorter lifetimes too
Diesels in industrial trucks are large low revving engines, they have narrow powerbands and require a large selection of transmission gear ratios. They are also designed for multiple rebuilding during their lives. Add to the fact they stink up the air and make it very difficult to be around one without choking and puking

 

[Scott Danforth]

I was wondering why outboards seem to have so many engine problems compared to car engines.

because people maintain their cars......and because a car motor only needs to produce 10% of its power to keep the car cruising down a highway at posted speed. Your boat uses 100% of the motors power on the hole-shot and about 60% at cruise

 

[thatone123]

Good answers! Agree with the diesel smoke, when I get behind one wish I could toss a grenade. Never understood how they got away with making those stink pots legal. Ok, that makes sense that the car engines are seldom put to the limits like outboards are. What about the harmonic vibrations of 4 strokes vs. 2? 4 strokes have higher compression compared to 2 strokes is my understanding because they need it to try to equal the acceleration of the 2's. In light engines this produces a lot of strange effects (vibrations and stress) that lead to shorter life? This is what I have read anyway.

 

[thatone123]

People maintain their cars??? You must come across different people than I do.

 

[thatone123]

I overheard some commercial fisherman lamenting how you still see 2 stroke engines that are very old, but still running. They said you don't see many used 4 strokes although they have been around for what...25 years now.

 

[jbuote]

Still not an expert (lol)...
This is interesting though..

I might consider the commercial fisherman's comments to be more like there aren't many used 4 strokes compared to 2 strokes, because the first owners aren't giving them up?...
(Ok, maybe not, but it's one interpretation.. )

As for longevity and people maintaining cars..
Most folks will get the oil changed.. That's it.. (in cars..)
Just doing that, they can go to 75K miles minimum usually.. (More if air filter, pcv valve etc.. are maintained..)
Cars also average about 12-1500rpm in cruising (I think it is anyway..).. That's almost Idle on muffs for most outboards..

To maintain an outboard, we're looking at what?
Oil changes in 4 stroke (same as cars)
2 strokes.. Gas/oil mix.. Were we off a little one time or another (increased wear..)
Winter storage if applicable (water drained? Freeze damage)
Water pump/impeller...

Not to mention, most people aren't running their cars through puddles each and every time they use them.
We're running through the best puddles with our outboards!!

I know general aviation mandates that a private registered aircraft not used for hire must have an annual inspection.. Period.

If commercially used, it's every 100hrs..
I have my pilots license, but unfortunately am not current but I believe these still apply.. lol

Most small aircraft (Cessna 150, 172 I'm familiar with) average a constant (not 22-25k, but rather 2.2-2.5k) rpm depending on altitude, climbing/descending etc....
(Edit: Yes, these are air cooled, so a bit different, but still...)

Our outboards, for peak HP run in what.. (not 44-55, but rather 4.5-5.5k) rpm??

Long story short(ish..)
I can certainly imagine an outboard of either type (2 or 4 stroke) having issues if not maintained meticulously..
Based on aviation standards, we should inspect our outboards every 1/2 year, or 50 hours..

But this isn't aviation.. It's pleasure boating in most cases..

What's considered maintaining a car can pass..
The same level of maintenance will not pass on an outboard..

I've learned that much so far..

Perhaps vibrations play a part in 4 vs 2 stroke, but if maintained per manufacturers guideline, it shouldn't be a problem right?

Once again, I'm not trying to be a wiseguy, but rather adding my thoughts to an interesting topic.
If I'm wrong on ANY of this (and I very well could be quite wrong), I hope to learn from it..

I am, after all, quite new to outboards...

Thanks!
Joe

 

[jimmbo]

Time will tell about the 4 strokes Longevity. There are more parts and systems to break/wear out, compared to old carbed 2 strokes. The newer 2 stroke DI models have nasty hard to troubleshoot electronics as well.
In the 60s the design life of OMC outboards was 1000 hrs under load at WOT. At the time, an auto engine subjected to the same conditions probably would have experienced a horrible twitching death way before 300 hrs. In either case engine life would be extended considerably by running at less than WOT. That was one of the reasons for the ever increasing horsepower race during the 60s, 70s, and 80s.

 

[jimmbo]

Most small aircraft (Cessna 150, 172 I'm familiar with) average a constant 22-25k rpm depending on altitude, climbing/descending etc....


Our outboards, for peak HP run in what.. 45-55k rpm?

I think your numbers are a little high

 

[jbuote]

Yup..:facepalm:
(I did say I wasn't current on the pilots license.. I guess the decimal goes 1 digit to the right for each few years I don't get checked out to fly again... HAHA!! :laugh: )

2.2 - 2.5K rpm... (sigh...)
Thanks for pointing that out jimmbo

 

[Scott Danforth]

a lawn mower that is never maintained (no oil changes) will get about 7 years of use prior to the motor seizing from lack of oil based on the test fleet from a prior life.

a car that has no oil changes and running on straight dino-squeezings will get about 20,000 - 25,000 miles prior to the oil coking so bad the motor seizes. synthetic raises that to about 25,000-30,000. simply changing the oil every 10,000 miles will keep the car running for about 100,000 miles or more. change oil every 3000-5000 miles and change the coolant every 5 years and the car engine will run to well over 300k.

boat motors run wet exhaust, the run at too low a temperature, and very few people actually maintain the motors. most boat motors are murdered from either lack of winterization, lack of oil change maintenance, or lack of exhaust system maintenance. still, with the minimal amount of recommended maintenance, the average I/O motor will make 3000 hours prior to needing a rebuild. that number goes to about 4000 hours if there is a heat exchanger on the motor and the motor is allowed to run at 170 degrees or higher.

as far as diesel technology, many diesels are just as clean as their spark ignited cousins when they leave the factory. then the owner plays with the fueling so they can "roll coal" there are diesel outboards out there. they just are not big in north america. diesel inboards are everywhere. most will go about 5k hours prior to needing a rebuild. these are designed to be rebuilt, many cases while still in the boat.

as far as harmonics, that is a function of firing angle, number of cylinders, etc. most of that can be balanced out in design of the motor and really doesnt impact longevity of the motor itself, its usually some ancillary bracket that breaks.

 

[82rude]

Scott I just watched a program on diesel motors .More efficient ,approx. 30 percent more mpg than similar gas motors and the new low sulfur fuel is much much better.Thats the smell jimmbo hates for what ever reason it maybe.Per gallon on the old diesel fuel you got over a large tablespoon of particulate matter coming out the tail pipe.The new fuel on the exact same motor will produce one drop from an eyedroppers worth.They claim that the best hybrid's will or could be diesel /electric in cars and trucks.People that change their settings on their trucks to roll coal should be fined heavily.Its just plain wrong and has no redeeming qualities atall.I will be looking at the new cruze diesel and used vw ,s shortly.

 

[Sea Rider]

Will contribute with my sand grain from experience in elucidating why OB's lasts way less than cars...

Internal salt formations inside water paths is a real silent OB killer. There's the erroneous idea that any OB conveniently flushed with fresh water after use will remain impeccable clean. This is a falacy, check pic. It's from a 500 hours used 2 cylinder powerhead religiously well flushed with fresh water for at least 10 minutes after each outing throughout the whole year. Imagine what will find inside a 3-4-6 cylinder powerhead constantly used year round and flushed excatly same..Now imagine a commercial used OB...



Due to constant ON/OFF cycles OB will start to build microscopic salt layers one in top of the other. even building salt crusts that lessen and restricts cooling water passing through powerhead.

In the long run if conveniently flushed or in the short one if never flushed, OB will start to work much hotter. Can check that testing with a temp gauge right out from box and with extended use to check temp differences. When OB's starts to use the Krypto green stuff as in cars will stop building salt layer internal formations along dangerous temp issues that could lead to severe OB overheat.

An OB working with higher temp than when out of the box will definitely wear out cylinder, piston, piston rings faster. I'm probably the only boater tearing powerhead each 500 worked hours to clean mechanically all internal water paths to factory cond, it's the only proven way that assures perfect coolling temp throughout the whole powerhead at any throttle range.

Add to this salt issue a cocktail of bad or incorrect heat range plugs, incorrect timing advance, running with removed thermo and using crappy 2 strokes TCW-3 oil and will have a clue why OB's lasts way less than cars..

Happy Boating

 

[racerone]

Fact----Outboards are really well built.-------Fact-----Owners invent new ways to destroy them almost every day.-----Ways include but not limited to falure to maintain cooling system.----Failure to maintain gear box oil and keeping water out of that gear box.-----Hitting submerged objects.----Running with the wrong prop.-----Using cheap / improper oils.----Allowing carburetors to plug up when motor is dormant ETC, ETC.-----People just do not know how to operate / maintain fine machinery in a harsh environment !!

 

[racerone]

123-----How much horsepower does it take to move a vehicle on a level road at 60 miles/ hr.----Say a small car -----Post your number.----And say a full size pick up with a 5.7 hemi engine,---post your number.-----Or if a vehicle has a 200 hp motor how much of that do you need to go 60 miles / hr ???

 

[Sea Rider]

A car, pick up with moster emgine has less tire drag to deal with while moving on a paved road compared to a boat which has huge hull drag to deal with compared to, needs more throttle and consequently operate at way more rpm being water 1K times dender than air.. Anyway, an OB runs at 4-6 K wot rpm near constantly compared to a car rpm while in fourth or fifth gear.

Regarding your previous post which is quite true and plainly in agreement with, nothing has yet been invented to deal with human stupidity..

Happy Boating

 

[GA_Boater]

If we let our cars and trucks sit in the off season and only used them on Memorial Day, 4th of July and Labor Day weekends and then drove them at WOT or close to it for hours - We would be complaining about how crappy cars and trucks are today. The older the vehicles are, the worse it gets.

Boats are the same, lack of use causes more things to go bad than regular use. And boats are used in a more hostile environment. Not many of us drive over logs, smack boulders or run sand/silt through the cooling systems during the drive to work or on vacation.

 

[Scott Danforth]

you forgot leaving fuel in it for 3 years, forgetting the drain plug and submerging the motor..... as I stated prior, boat motors are murdered

 

[thatone123]

I have always figured that at cruise many vehicles only take 1 hp per mile an hour to operate. So at 60 mph you only need 60 hp. Yet we drive trucks and cars with hundreds of hp. I have had small sports cars (that I work on) that are fast with only 100 hp or so. Good answers all. I have seen the OMC 15's with over half a box of Morton salt in them STILL running??? I think because some race developed outboards have 1 carb (older motors) and the complexity of this and syncing properly (almost impossible) is one reason they have a lot of cylinder problems compared to car engines. New car and OB engines have similar fuel injection so who knows. I think that a new type DI 2 stroke outboard would last longer than a 4 stroke, but for the electronics that are hard to sync exactly all the time, because of more harmonic stress in the 4 stroke from higher compression in a fairly light engine turned on its head.

 

[thatone123]

opps///I meant that the old carb outboards had 1 carb per cylinder...