How Does a Small Four Stroke Outboard Die?

[a64pilot]

Have you had one die on you? How long did it last? Was death a sudden event, spun bearing, dropped valve, thrown rod, or did it die a slow death, burning oil, losing compression getting hard to start.

I’m trying to see how long they live and what was the cause of death to try to determine mines lifespan and whether or not it will give warning slowly over time or not.

Wondering how many years or hours one of these things will live.

I’m mostly talking 9.9 to 20 HP or so, I assume they out live their little Brothers

[Diesel Bill]

Hi a64pilot. I think most small engines die from neglect. I've lost one when the coils got to weak to fire the plugs, another when the crankshaft upper seal quit sealing. Mostly as a young teenager I was rough on my engines. Now 60 years later I treat them more gently.
Lots of engines (outboards) are put away with old gas in the carbs and not flushed to get rid of salt. Just my 2 cents.

[Jammer]

Originally Posted by a64pilot

Have you had one die on you? How long did it last? Was death a sudden event, spun bearing, dropped valve, thrown rod, or did it die a slow death, burning oil, losing compression getting hard to start.

I’m trying to see how long they live and what was the cause of death to try to determine mines lifespan and whether or not it will give warning slowly over time or not.

Wondering how many years or hours one of these things will live.

I’m mostly talking 9.9 to 20 HP or so, I assume they out live their little Brothers

My grandfather had a 1965 18hp Johnson that he used for fishing. I would guess it got close to 100 hours a year and was still operable when I finally sold it in the 1990s. So 25 years and probably over 2000 hours. I believe he had to have the cylinders and pistons replaced at one point, among other repairs.



I have two 3.5 hp Johnsons from the 1960s that are still running OK. They are relatively new to me so I don't know the full service history. Each one is on its second ignition system, the fuel system components have been cleaned, and the gearcase seals replaced multiple times. Typically the smaller motors aren't run much.


It is my experience that it is rare for outboards to fail from cumulative engine wear. 9.9 through 25 horsepower motors are very common here for fishing, along with somewhat larger ones at least on larger lakes. My cousin works as a part-time fishing guide and probably puts 300-400 hours a year on his boat motor. While a good deal of this is trolling at idle speed, that's still pretty hard use. He had a 35 hp on his last boat which he bought new about 10 years ago and sold last year. I don't think he did anything to it other than routine maintenance every year.


I believe that most outboard motors that get scrapped have had something happen to them. Hit a rock, seal failure in the gearcase leading to them being run without gear oil, lubrication failure especially in the 2-cycles that had an oil injection pump, or premix 2-cycles that were run on straight gas, motors that were immersed, motors run with no cooling due to impeller failure. Some get scrapped due to parts availability problems -- you can still get parts for 50s/60s Johnson/Evinrude because they didn't change them for a decade and there are so many out there, but for the 70s/80s motors some of the parts are starting to dry up.


But they're water cooled engines, should run for 2500 hours if you take care of them

[thomm225]

It appears from reading your posts that you take care of your equipment so I'd say your 4 stroke will last as long as you want it to

I had a 1960's vintage (Homelite) Bearcat 55 hp 4 stroke back in 1976. Some of those are still running

Any Btw, my 5 hp 4 stroke is 8 years old and I flush it (with fresh water) once or twice a year whether it needs it or not! I run it minimum once a week in season and at least once every two weeks in Winter.

https://www.youtube.com/watch?v=4gUnhcYLTdE

[Shrew]

The vast majority of issues with both 2 adn 4 strokes are carburetor related. Typically carb issues on 2 strokes are bad fuel or rich mixes. Carb issues on 4 strokes are typically just bad fuel/ethanol related.

Coming in second on 4 strokes are valve adjustments (tuning).

I still carry a small toolkit and a spare sparkplug(s) but have never used either in the last 12 years. That includes a 15-year-old Honda 2 HP. The old days of unreliability were more related to 2strokes running rich (fouled plugs) or lean (heat related issues).

Back then ring and valve jobs were not uncommon.

I run the carb dry when it is going to sit for any length of time. I use copious amounts of startron and stabile (marine for ethanol) all the time.

Replacing the carb every 5-8 years is just slightly more costly than a proper rebuild and takes significantly less time.

[Shrew]

If I were having a hard-starting 4 stroke I would do the following:

1) Try to clean the carb
2) Replace the carb
3) adjust the valves

[a64pilot]

So, it’s sounds as if wearing out isn’t common?
I was wondering if failures were often things like thrown rods, swallowed valves which can happen with little warning or were they loss of power. Burning oil, hard to start from low compression kind of death.

So why do people get new outboards if they seldom seem to wear out?

[Jammer]

Originally Posted by a64pilot

So, it’s sounds as if wearing out isn’t common?

Right.

I was wondering if failures were often things like thrown rods, swallowed valves which can happen with little warning or were they loss of power. Burning oil, hard to start from low compression kind of death.

The usual reason an outboard that has been working just fine fails while under way is ignition problems. The newer, fuel-injected ones can also fail because of problems with the fuel injection systems.

I've never heard of an outboard that threw a rod. I suppose it happens.

So why do people get new outboards if they seldom seem to wear out?

Hitting rocks, immersion, etc.


Parts and service availability problems for engines over about 25 years.


Desire for different HP, shaft length, electric start, power tilt, etc.; replacement as part of replacing the whole boat



Frustration with inability to make lasting repairs. Fuel system problems can be tricky and even full-time mechanics miss stuff. Many people are unwilling to do enough service, beyond a certain point you're on borrowed time if you don't replace *all* the rubber components in the fuel system which includes a new fuel pump and a carb rebuild or replace as well as a new hose, connectors, and tank fittings.

[deblen]

You are asking about 4 stroke outboards-not 2 stroke.


I bought a new 2HP (BF20) Honda in 1984. I have no idea how many hundreds(thousands?) of hours are on it. It has been used every summer for 5 months in salt & fresh water pushing a 12ft skiff. The skiff has been used as a tender in salt water since 2006 and as a fishing boat on a small lake before that.It's not very fast-probably 6mph wot,but I don't have to go far. The motor is severely overloaded by this skiff & advancing the throttle beyond 1/2 does not gain any RPM or speed. Early on it started smoking a little & using a bit of oil.It only holds a ltr,& I probably add a total of another ltr over the 5 mo.season. I change the oil & drain the carb bowl each fall & store it in my unheated shed each winter. I try to avoid E gas. Our hi-test gas is still alky free.No locals will put E gas in their small engines-regardless -lawnmower,outboard,etc. Bad white corrosion of aluminum carbs & jet blocking.

In the spring,with fresh gas,it generally starts 3rd pull.
I have had the same kind of service from small Honda engines in other equipment also. If a Honda doesn't start,there is probably crud in the carb.
I have many aquaintances that have had similar service from larger Honda outboards. I have no personal experience with other brands of 4 stroke outboards. I have no connection to Honda. I am just a very satisfied customer. They do cost a little more.

8 or 10 yrs ago,I helped a friend bring his new(to him) Southern Cross 28(30?) 100 mi. up the Maine coast to Grand Manan. The fuel tank was dirty,the filter kept plugging. We ended up putting his 11ft Avon with 5HP Honda on the port hip,locked the outboard turning swivel,& powered over 50mi.,while we sat comfy in the cockpit ,steering by tiller & making 6+ kts--better than her diesel would do.


Cheers/ Len

[thomm225]

Not a four stroke but another good old outboard still running fine:

https://norfolk.craigslist.org/boa/d...931546500.html

[Shrew]

Originally Posted by Shrew

Back then ring and valve jobs were not uncommon.

Correction: Back then, ring and Piston jobs were not uncommon.

[Shrew]

Originally Posted by a64pilot

So why do people get new outboards if they seldom seem to wear out?

I have a friend who buys used small engine equipment (lawnmowers, generators, snowblowers, etc) He buys them very cheap because in almost all cases they are not running.

He fixes them up and resells them used. He tells me he does the exact same thing to all of them.

1) He rebuilds the carb
2) He thoroughly cleans them
3) Lubricates all the moving parts

I honestly think people replace them when they are tired of them not starting or running properly.

[Pete17C]

Neglect!

I've got a 16hp 4 stroke on my sears suburban tractor, from the early 1970s, starts on one flick of the key, still runs good

I've replaced most of the ancillaries (starter/carb/exhaust/wiring) over the years, but it's never been torn down or rebuilt