Oil injection system failures in modern 2-strokes

[dandreye]

Hi All,

I've just come across a collection of several threads elsewhere on various automix (oil injection) system failures in 2-strokes, made up by an owner of Yamaha 90 AETOL who decided to shut down the Autolube system in his outboard hoping to avoid any such risks. Some of the posts in those threads mentioned failure of plastic gear in the system resulting from some rubbish/debris etc entering it, while some others reported severe oil supply shortages only to one of the cylinders caused by clogging of some oil hose supplying oil to that particular cylinder if I got it right. All the cases reportedly led to piston and/or cylinder wall scoring resulting in an expensive overhaul and at times even beyond repair (i.e. making it cheaper to buy another used outboard).

Looking at the parts diagrams and the pictures of the actual parts of my 2000-2001 Mercury 90 ELPTO I can see that:

- the gear looks metal and not plastic

- oil is injected into fuel hose in front of fuel pump and so should be supplied evenly to all 3 cylinders assuming of course the mix itself makes it there equally well through the carburettors

My oil injection system has been doing well so far (touch wood) but to carry on using it with peace of mind from now on I'd like to understand:

1) What does the statistics of the oil injection system failures look like on Mercury 2-strokes with the same or similar design and what exactly are the most frequent root causes revealed upon inspection? (I'm trying to create a checklist here to go through now and then hoping to prevent the issue)

2) Assuming reduced amount of oil in the mix inevitably triggers cylinder temperature rise, will a ring with a thermocouple under each spark plug connected to its own temperature gauge on the dashboard help notice the issue early if it still happens? If the figures are normally about the same (at particular rpms) I should be able notice a change in any of them pretty soon. Such kits are relatively inexpensive and I could easily afford installing 3 of them; also they may help signal some other issues with only one cylinder, so why not.

3) Which particular temperature is the standard CHT alarm in these outboards designed to buzz at anyway?


Many thanks in advance!

 

[ondarvr]

The rate of actual failures is exaggerated, normally it's from lack of maintenance or some other totally unrelated issue. The plastic gear was on larger Merc 2 strokes, and if the motor over heated the gear could soften and fail. I have a 2005 Merc 90 ELPTO and I don't lose any sleep over the oil injection system, they are very reliable, there are probably as many "I forgot to add oil to the gas" failures as there are oil injection system failures, you just don't hear about them because the blame is all on the owner.

​There are much bigger things in life to stress over, so the oil injection is way down the list, if I get the others things handled and get that far down the list I'll consider myself lucky.

 

[ThomW]

For what it is worth, I have a 1987 Merc Black Max 200, and the oil injector system on the old girl is still working fine!

 

[dandreye]

I have a 2005 Merc 90 ELPTO and I don't lose any sleep over the oil injection system, they are very reliable, there are probably as many "I forgot to add oil to the gas" failures as there are oil injection system failures, you just don't hear about them because the blame is all on the owner.

That's really encouraging to hear: tbh I was very much surprised myself to see that many failure reports now that the core 2-stroke design (incl oil injection system I suppose) has hardly changed over the last 2-3 decades, at least that's what I recall reading somewhere about my OB model.

There are much bigger things in life to stress over, so the oil injection is way down the list, if I get the others things handled and get that far down the list I'll consider myself lucky.

Very true ) Just trying to be as nice to my outboard as possible really. Also coincidentally specializing in early fault prevention over the last 20+ years I'm kinda abusing the skill and trying to apply it everywhere around myself, which does pay off in general..

 

[Johnson110]

What hp engines were those plastic gears used ?

 

[jimmbo]

More engines have failed from failure of operators to mix gas-oil than have failed from injection/premixing system malfunction

 

[dandreye]

Looks like (1) from my initial post is not that much of a concern if at all, at least with these particular outboards.

Any chance to comment on (2) and (3) too? What temperatures should one normally expect to have at the spark plugs of a healthy 2-stroke using proper oil? (as a function of rpms I suppose) I really fancy the idea of direct per-cylinder temperature real time monitoring as it might help notice other issues earlier rather than later too: at just ~$16 a sender+gauge kit it's much cheaper than dealing with any sort of the consequences.

 

[wn6ngp]

I also have a 2000 90HP ELPTO with about 350 hrs. Had the same concern but everyone on here just said to not let it overheat. Would you post the link on that $16 temp sender kit. I've got a shadetree hookup that watches the temp on the opposite side of audio alarm switch. It stays pretty cool like 120 deg or so even running hard. I like to watch gauges anyway.

I've also decided that since I go onshore and some offshore I need to buy the towing insurance. 1 incident would cost over $2000. Things happen.,

 

[jimmbo]

Looks like (1) from my initial post is not that much of a concern if at all, at least with these particular outboards.

Any chance to comment on (2) and (3) too? What temperatures should one normally expect to have at the spark plugs of a healthy 2-stroke using proper oil? (as a function of rpms I suppose) I really fancy the idea of direct per-cylinder temperature real time monitoring as it might help notice other issues earlier rather than later too: at just ~$16 a sender+gauge kit it's much cheaper than dealing with any sort of the consequences.

Why are you looking for Problems for your Solutions? If you use the correct plugs for the engine you shouldn't have to worry about plug temps, the engine engineers did. You will be spending more time monitoring the engine than enjoying boating. But, if that is your idea of fun... Just remember to watch where the boat is going and what the boats nearby are doing

 

[dandreye]

I'm looking at this one:
http://www.mytahometr.ru/shop/14/desc/cifrovoj-moto-termometr-mt-10
In fact with the 5m extension cable option it costs a bit more i.e. $22: sorry just noticed that $16 implies no extension, hence just 0.7m own cable.

No idea how much shipping it all the way to the US from there would cost but surely they'll be much surprised getting an international order as it's apparently targeted at a domestic market. I tried looking for similar kits on Ebay and AliExpress expecting to find them at a fraction of that price and strangely didn't see anything cheaper than this one (I live in the UK):
http://www.ebay.co.uk/itm/311479461308

Meanwhile there are many cheap ones from China costing just a few dollars with a thermocouple sender w/o a ring; also how exactly extending their cable would affect the figures displayed is unclear.

 

[dandreye]

Why are you looking for Problems for your Solutions? If you use the correct plugs for the engine you shouldn't have to worry about plug temps, the engine engineers did. You will be spending more time monitoring the engine than enjoying boating. But, if that is your idea of fun... Just remember to watch where the boat is going and what the boats nearby are doing

I guess it's just a professional disease after doing over 20+ years of early fault finding for living, which has actually paid off quite well elsewhere in my household so far ) Either way I don't mind having lots of gauges: this way it looks somewhat like an aeroplane dashboard and occasionally hints at a problem here or there that I'd otherwise be unaware of. The plugs are the right ones and so is everything else and I do my best watching around as the area is sadly full of not always so sober boaters. The actual driver behind all these questions is the attempt to minimize any possible downtime, which is critical in my particular circumstances.

 

[ondarvr]

I think you would need to test it yourself to see what the temps are when it's running correctly, then use that as the base line. Each cylinder may be a bit different due to how the water flows through the block.

​I forgot to add to my first response, I really don't care if a motor uses an injection system or pre-mix, and for those that are concerned they should just use the method or system they feel more comfortable with.

 

[dingbat]

The actual driver behind all these questions is the attempt to minimize any possible downtime, which is critical in my particular circumstances.

Using the boat on regular, year round basis is the best PM you could ever do. The more you use them the less problems you have.

Don't waste your time setting up a "command center" at the helm. Maintenance schedules are based on annual usage, not service hours. That should tell you something about the system's propensity for failure.....Over 6,000 hours at the helm (both recreational and competitive) and I've not had a single preventable failure in all that time. This is coming from a guy who understands 99.8% up times all to well (industrial equipment mfg.)

Do the annual maintenance, change water pump impeller every 2-3 years, keep fresh fuel and oil in the tank(s) and go boating. Everything else is circumstantial


Gotta ask, why is your particular circumstance critical?

 

[dandreye]

I think you would need to test it yourself to see what the temps are when it's running correctly, then use that as the base line. Each cylinder may be a bit different due to how the water flows through the block.

That's the plan so far. wn6ngp reports ~120 degrees above (sorry I must admit I couldn't understand what that shadetree hookup means) but assuming 120F is implied that looks more like cooling water temp as that's exactly what the thermostat in my outboard model is rated for. Meanwhile the gauge in the kit I was referring to above can display -40C (-40F) to 120C (248F), so normal temperature at the spark plug should be somewhere within this range.

 

[flyingscott]

Forget about the temp gauges as those with the thermo-couple under the spark plug are unreliable. Instead of overthinking this put a good water-pressure gauge in and go boating. Unless you are constantly watching the gauges how will you know it overheats before it's to late. If the motor runs out of oil it or runs lean on oil that gauge will tell you nothing. And If your motor runs out of oil or runs lean you are screwed before that gauge will tell you anything. Normal temp at the plug will be higher because the plug is not cooled by the water jacket.

 

[dandreye]

Using the boat on regular, year round basis is the best PM you could ever do. The more you use them the less problems you have.

Allright (alongside answering why any downtime is critical), to keep the story short, at present we can only spend 3 weeks (summer holidays) in the area where the boat is moored, which is when my family and I literally don't leave the boat. Any single failure that requires parts swap and the boating is over until our next summer holiday while everyone's out there boating in that perfect weather. At present I stock several parts that look more vulnerable than average to the mechanic that helped me go through my outboard design. This summer starter relay died, so I pulled a spare one out of the garage. Meanwhile as you say there's always a chance for something else that we missed to fail and only buying an entire spare used OB exactly like mine (~$2.5K in good or fair condition) however mad it may sound can guarantee minimal downtime as long as the boat itself is safe and sound. If that's what it takes to ensure everyone's happy no matter what then so be it: boating is never cheap anyway. Btw that's exactly what businesses in the industry I'm in (telecoms) do to minimize any downtime: they just install more than one instance of everything that may possibly fail thereby eliminating any single points of failure.

Overall I do my best looking after it incl proper winterization every autumn etc. and it's been paying us back with reliable operation so far (touch wood again).

Btw the more I lately read on modern 4-strokes' reliability the more I like this somewhat old fashioned yet bulletproof 2-stroke: will definitely keep it for as long as it lasts.

 

[dandreye]

Forget about the temp gauges as those with the thermo-couple under the spark plug are unreliable. Instead of overthinking this put a good water-pressure gauge in and go boating. Unless you are constantly watching the gauges how will you know it overheats before it's to late. If the motor runs out of oil it or runs lean on oil that gauge will tell you nothing. And If your motor runs out of oil or runs lean you are screwed before that gauge will tell you anything. Normal temp at the plug will be higher because the plug is not cooled by the water jacket.

I thought it'd take a while i.e. several dozen seconds or perhaps even several minutes before it overheats triggering the buzz?..

 

[flyingscott]

I thought it'd take a while i.e. several dozen seconds or perhaps even several minutes before it overheats triggering the buzz?..

No they have a safety margin built into them. The mistake people make is to keep running them after the buzzer goes off. The buzzer wouldn't do much good if it went off after it overheated.

 

[dandreye]

Hmm those people must be really "sound proof": I can barely stand the beeping buzz that goes off well before all the oil's gone, which I guess is another safety margin at work ) Anyway good to hear that even standard CHT alarm alone is good enough to rely on.

 

[Scott Danforth]

Using the boat on regular, year round basis is the best PM you could ever do. The more you use them the less problems you have.

Allright (alongside answering why any downtime is critical), to keep the story short, at present we can only spend 3 weeks (summer holidays) in the area where the boat is moored, which is when my family and I literally don't leave the boat.

you have to use the boat more than 3 weeks a year. sitting ships go to s#!t. as dingbat said, use it.

use the boat to simply ride around in and burn fuel. use it to go fishing. that way, when you and your family need it on vacation, its there.

most failures of outboard come from lack of maintenance. items to be replaced every 2-3 years are calendar events, not hour of use events.

cooling system maintenance is the key to keeping the motor cooling properly. things like impellers regardless if you ever fire the motor or not, get replaced as a calendar event - this is one area where people cant wrap their head around the notion of replacing something they havent used.

fuel system maintenance is key to the motor running well. this means keeping fresh fuel in the tank. (use the motor)

when motors sit, linkages corrode, critters build nests in the cowl, rubber parts go dry and permanently deform, fuel goes bad.... then when you need the motor it fails. when motors are used often you get so many more pleasant memories