Disabling the oil mixing system '83 40 Hp Mercury

[flyingdelorian]

The motor is 26 years old but new to me. I think the oil mixing is working but I would rather mix my own gas than worry about it failing and ruining my motor. This would kill my pontoon boat since I can't afford to replace the outboard or even have it re-built. I have been searching around the internet and have run across several different opinions but mostly for larger HP Mercs. I have noticed the initial alarm beep when I turn the key on that I just discovered was the warning alarm for overheat and the oil mixing system. Can I mix my gas and just stop putting oil in the reservoir?
I would like the overheat alarm to still work. I am unsure if all I have to do is unhook the sensor wires for the oil and if so where they are located. I am pretty handy but since this is my first outboard, I am leary of assuming things.
If I do mix my own gas, I am assuming a 50 to 1 ratio is appropriate for this motor.
Thanks for a great site and all your helpful input!!

 

[chris.olson]

Re: Disabling the oil mixing system '83 40 Hp Mercury

If I do mix my own gas, I am assuming a 50 to 1 ratio is appropriate for this motor.​

Thanks for a great site and all your helpful input!!

The oil injection system is ridiculously simple, and therefore pretty darned reliable on those old oil-injected Mercs. The problem with disabling it is that if you don't run oil thru the pump, the pump will seize and strip the teeth off the pump driven gear.

The other problem is that it doesn't run a set fuel/oil ratio. The amount of oil injected into the fuel stream increases with engine speed so it runs "richer" at full throttle than it does at idle due to the oil flow from the pump increasing faster than fuel flow as engine speed increases. I think 50:1 is too "lean" for full throttle operation, but will be fine at idle and slower speeds. I believe correct full throttle fuel/oil ratio is closer to 20:1.​

The only way I know of to "disable" it is to remove the pump and install a blocking plate on the pump mounting boss on the crankcase, then unplug the low oil sensor harness and jump it so the alarm doesn't sound continuously (it requires a small current that travels thru the oil between the leads of the sensor harness to keep it from activating).​

I'd leave well enough alone. I've never seen a oil injection pump fail unless it got dirt into it. If you're worried about the drive gear failing, pull the pump and inspect it. If you see the plastic driven gear starting to "hourglass" install a new gear - they're not even very expensive.​

If you want a little "safety cushion" you can do like I do when I have taken one of these engines apart for service - I mix the fuel with oil at a 50:1 ratio WITH the oil injection pump operating until I'm certain the oil injection system has bled itself and is operating normally. All it does is smoke a bit more until that tank of fuel is used up.
--
Chris​

 

[chris.olson]

Re: Disabling the oil mixing system '83 40 Hp Mercury

I think 50:1 is too "lean" for full throttle operation, but will be fine at idle and slower speeds. I believe correct full throttle fuel/oil ratio is closer to 20:1.​

I went and read my manual, and it seems these older "constant ratio" oiling systems are supposed to inject oil at right around 50:1 all the time. So it's possible that mixing the fuel/oil ratio at 50:1 would be adequate if you removed the oil injection system.​

However, from experience with 40 hp four-cylinder models (I believe yours is a three cylinder?) I know the so-called "constant ratio" oiling delivers a slightly richer oil mix at full throttle than it does at idle. But it's probably not 20:1 like I had alluded to (at least according to the manual) because skipping ahead to the variable ratio oiling used on the larger Mercury outboards indicates that they operate from 100:1 at idle to a rich condition of 50:1 at full throttle.​

It doesn't really say what the correct fuel/oil ratio is for an oil injected engine with constant ratio oiling because it's not adjustable - merely to mix the fuel with oil at a 50:1 ratio for breakin (with the oil injection system operating normally), which would presumably run the engine with double the normal amount of oil during breakin.
--
Chris​

 

[flyingdelorian]

Re: Disabling the oil mixing system '83 40 Hp Mercury

Here's a twist. Same question only I just discovered that I read the serial number wrong in an earlier post. I just went and double checked and it is a '95 model not an '83. I miss read a 6 for a G. It also looks like the alarm for the oil tank level is already unpluged. I think someone was already mixing the gas and put the mixer back in service to sell it. Any thoughts?

 

[chris.olson]

Re: Disabling the oil mixing system '83 40 Hp Mercury

I just went and double checked and it is a '95 model not an '83

That's quite a difference (12 years), but the concept is the same. If it's a '95 this is the powerhead you got, and it's a four-cylinder:
http://cid-0efeb4f5150fdce3.skydrive.live.com/self.aspx/Alumacraft Backtroller 14/HPIM1140

That engine has a little magnetic float switch in the bottom of the oil tank that senses low oil level. If the magnet falls off, which is fairly common, the alarm sounds all the time and the "quick fix" is to disconnect the harness from the switch. You can't replace the switch seperately - you have to replace the whole oil tank. More than likely, that's the case.

Again, I'd leave it oil-injected. I've never seen the oil pump fail on one of these engines. The one in the photo is a '91 and has over 3,000 hours on it. It's had pistons and rings, crank bearings and seals, broken reed block, blown exhaust cover gaskets - has been apart numerous times for repairs - but still has the original oil pump and gears in it.
--
Chris​

 

[Rowroy]

Re: Disabling the oil mixing system '83 40 Hp Mercury

I wouldn't hesitate for a second to remove the oil injection. In my oh-so-humble opinion, Mercury created a fix for a problem that never existed. 50:1 will do the trick for ya.

Here is a little light reading . . . .

http://bassinhound.net/fishing/inject/

 

[chris.olson]

Re: Disabling the oil mixing system '83 40 Hp Mercury

Mercury created a fix for a problem that never existed. 50:1

Being a mechanic for 31 years, I'd have to say that's not totally accurate. The shelf life of pre-mixed fuel and oil is considerably shorter than straight gasoline. Modern gasoline contains oxygenates, usually ethanol, with which two-stroke oils don't mix. Two-stroke oils contain solvents to facilitate mixing with gasoline, which combined with the "dry" ethanol used as an oxygenate, evaporates and causes seperation of the oil/gas pre-mix.​

Suzuki figured out a long time ago, on both outboard and motorcycle two-strokes, that it's better to do the mixing in "real time", just prior to the fuel and lubricant entering the engine, or in the case of their CCI engines, to do it in the intake port independent of the carbs. Everybody else followed suit.​

Oil injection has been around on two-strokes since the early 70's and is a proven system. I wouldn't disable it on the premise that it MIGHT fail. That's like mounting your fuel tank higher than the carbs to gravity feed the fuel to the engine on the premise that the fuel pump might fail, causing a cylinder to go lean and burn a piston.
--
Chris​

 

[Rowroy]

Re: Disabling the oil mixing system '83 40 Hp Mercury

Being a mechanic for 31 years, I'd have to say that's not totally accurate. The shelf life of pre-mixed fuel and oil is considerably shorter than straight gasoline. Modern gasoline contains oxygenates, usually ethanol, with which two-stroke oils don't mix. Two-stroke oils contain solvents to facilitate mixing with gasoline, which combined with the "dry" ethanol used as an oxygenate, evaporates and causes seperation of the oil/gas pre-mix.​

Suzuki figured out a long time ago, on both outboard and motorcycle two-strokes, that it's better to do the mixing in "real time", just prior to the fuel and lubricant entering the engine, or in the case of their CCI engines, to do it in the intake port independent of the carbs. Everybody else followed suit.​

Oil injection has been around on two-strokes since the early 70's and is a proven system. I wouldn't disable it on the premise that it MIGHT fail. That's like mounting your fuel tank higher than the carbs to gravity feed the fuel to the engine on the premise that the fuel pump might fail, causing a cylinder to go lean and burn a piston.
--
Chris​

Well, I wear my seat belt on the premise that I MIGHT be in an accident. I also wear my kill lanyard on the premise that I MIGHT fall out of the boat. Will either of those events occur? Anything's possible, but I can do as much as possible to prevent the outcome from being any worse than is has to be.

However without turning this into a pee pee contest, ethanol DOES mix with oil. It has a property called miscibility (look it up). This is what makes it so versatile.

I guess that everyone who is running an outboard without oil injection should retrofit their motor, right? After all, those motors that I see on the lake that were made in the 50's and 60's must be doomed.

Bottom line: He wants to remove his oil injection and is asking for help. Period. He doesn't need folks telling him why he may or may not be making a bad decision.

 

[chris.olson]

Re: Disabling the oil mixing system '83 40 Hp Mercury

However without turning this into a pee pee contest, ethanol DOES mix with oil. It has a property called miscibility (look it up).

Being you're a chemist, the word "ester" should provide a clue. Petroleum two-stroke oils do not mix with alcohols of any sort. Period. Only expensive sythentic two-stroke oils, which are an ester of vegetable oils, will mix.​

It matters not to me whether somebody wants to disable their oil injection system and go back to the stone age of two-stroke technology. I'm just pointing out that oil injection is better than pre-mixing because it provides more precise lubrication for your two-stroke engine, and is not reliant on miscibility. The vast majority of massive failures I've seen in oil-injected two-strokes is not due to failure of the oiling system, but by water intrustion or lean-condition burn-down.​

Take it to an extreme, disable the oil injection on a DFI OptiMax running it on pre-mix, and your warranty is void. I never hurts to consider all available information before doing something that you're not totally sure of, much less of not being sure of how to do it.

The original poster stated he has a pontoon and doesn't trust the oil injection on the premise that it might fail and he doesn't have the money to fix the engine if it does. So there's factors to consider - modern fuel is many times blended up to E-10. Alcohols are hydroscopic and you're operating in a marine environment. Even sythentic oils don't mix with water and I've never seen ethanol blended fuel that is totally anhydrous. Therefore I'd recommend servicing the oil injection system if you're not totally sure that it's working properly, and go have fun and quit worrying about it. It eliminates all the variables that older engines have to put up with with today's fuels.
--
Chris​

 

[Rowroy]

Re: Disabling the oil mixing system '83 40 Hp Mercury

Being you're a chemist, the word "ester" should provide a clue. Petroleum two-stroke oils do not mix with alcohols of any sort. Period. Only expensive sythentic two-stroke oils, which are an ester of vegetable oils, will mix.​

It matters not to me whether somebody wants to disable their oil injection system and go back to the stone age of two-stroke technology. I'm just pointing out that oil injection is better than pre-mixing because it provides more precise lubrication for your two-stroke engine, and is not reliant on miscibility. The vast majority of massive failures I've seen in oil-injected two-strokes is not due to failure of the oiling system, but by water intrustion or lean-condition burn-down.​

Take it to an extreme, disable the oil injection on a DFI OptiMax running it on pre-mix, and your warranty is void. I never hurts to consider all available information before doing something that you're not totally sure of, much less of not being sure of how to do it.

The original poster stated he has a pontoon and doesn't trust the oil injection on the premise that it might fail and he doesn't have the money to fix the engine if it does. So there's factors to consider - modern fuel is many times blended up to E-10. Alcohols are hydroscopic and you're operating in a marine environment. Even sythentic oils don't mix with water and I've never seen ethanol blended fuel that is totally anhydrous. Therefore I'd recommend servicing the oil injection system if you're not totally sure that it's working properly, and go have fun and quit worrying about it. It eliminates all the variables that older engines have to put up with with today's fuels.
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Chris​

I always love it when folks of one discipline try to be experts in another . . . like mechanics trying to be chemists . . . always entertaining.

I realize you were probably taught that by another so-called "expert" with whom I could never compete, so rather than try to point out the many, many flaws in your chemistry lecture, I'll just step aside and say, "Okay". I just hope you take the time to do some actual research and learn what these words mean that you keep throwing around. I would recommend taking a class at your local community college.

 

[chris.olson]

Re: Disabling the oil mixing system '83 40 Hp Mercury

I just hope you take the time to do some actual research and learn what these words mean that you keep throwing around. I would recommend taking a class at your local community college.

While I believe a person never stops learning, I do have a degree in mechanical engineering from the University of Minnesota and have worked on internal combustion recips most of my adult life - the vast majority of that time for Cummins on marine and stationary diesel applications. But never assume that I am stupid.​

I'm also intelligent enough to not have to degrade myself to personal attacks because my opinion doesn't agree with somebody else's. I would expect the same in return.
--
Chris​

 

[flyingdelorian]

Re: Disabling the oil mixing system '83 40 Hp Mercury

I just type a 4 page reply. (exajuration) and the thing siad I wasn't logged in.
Ahhhh

 

[flyingdelorian]

Re: Disabling the oil mixing system '83 40 Hp Mercury

Ok, I am told that I am a bit paranoid. I must make this motor last 4-5 years in order for it to be a good investment. If I kill it bfore the , I have another scrap of aluminum in my yard. According to the smoke I see and the oil usage from the reservoir, the oil system is working. Is there a way to check?
I am a computer tech by trade, so I know that a pound of prevention is worth 2.5 tons of cure. I want to do what is best and I like the sound of letting the oiling system do it's job but if the alarm is disabled, am I not at the mercy of chance? ( There are Murphys in my blood line.)
I appreciate both opinions.
I am just looking for the best solution to keeping this 95 model running as long as possible without spending money. What will it take to maintenance the oiling system and put the alarms back in service?

I'm no engineer or chemist. If you need advice on your PC then I'm your man.

 

[James P]

Re: Disabling the oil mixing system '83 40 Hp Mercury

Thanks for your words Chris. I recently disabled my oil injection because of the warning beep always going off. I also have read many posts about the module going out which is about $200 and the magnet on the float falling off and having to buy the entire tank. I'm guessing if I was the type of boater that was constantly on the lake I probably would have never had that beep to start with. I'm not sure. Mine all started when I checked the fuel pump and maybe got air in the line to my oil injection. I don't know! I'm still reading and learning and maybe I needed to just bleed my line once I checked my fuel pump because of air in the line. It's still all confusing but I believe you when you say it's reliable. At this time I'm able to find gas other than the 10% alcohol so I'm thinking my premix will mix like it's supposed to. When it gets to where I can't buy the non alcohol I'll begin using the synthetic and that does give me peace of mine about knowing that. I still have all my oil injection parts so maybe when I become even better educated I'll hook it up again.

 

[chris.olson]

Re: Disabling the oil mixing system '83 40 Hp Mercury

What will it take to maintenance the oiling system and put the alarms back in service?

First, I had the carbs off my Mercury 40 ('91 model, but it's the same as yours) this afternoon and specifically looked at how one would disable the oil injection on one of these. Mercury does not make a block-off plug or plate for the oil pump on these engines like they did for the V-6's. And you just can't simply remove the pump because that will change the crankcase volume and you'll have two lean cylinders.​

If I was going to disable it I'd remove the injection check valve/Tee assembly in the fuel line, then put a "loop line" on the oil pump so it would pump oil in a circle. As long as the pump is on the engine it HAS to have oil or it will eventually sieze.​

Mercury has never monitored oil flow - the VRO pumps have a rotation sensor that only alarms if the pump stops rotating - it doesn't tell you if oil is actually flowing. And they have a low oil sensor in the tank. All YOUR engine has is a low oil sensor and in my way of thinking it's no big deal if it don't work because you have sight tube and you can always see how much oil is in the tank. You can't replace the sensor, if it's bad, without buying a whole new oil tank assembly.​

Again, about being paranoid - I have NEVER seen the oil pump fail on one of these. Black Max V-6's? - Yeah. But never one of these.​

Here's how I verify that it's working properly. Take the cowl off and make sure the engine is level with the oil tank, say, half full. With a marker pen, make a mark on the tank at the top of the oil level. Add a measured amount of oil - I like to use 10 ounces. Make another mark on the tank at the new oil level. Fill your gas tank and go run it until you use your measured 10 ounces of oil out of the tank.​

Refill your gas tank - you should use very close to 3.9 gallons of gas @ 50:1. I've found that if you, say, backtroll with the engine all day you'll use almost a full tank to use 10 ounces, meaning that it's running at around 60:1. If you run the engine harder, like you might on a big pontoon, you'll tend to use your measured 10 ounces in more like 3.7 or 3.8 gallons of gas, meaning it's running at about 48:1. If you run it flat out, like I do most of the time, I've seen it use 10 ounces of oil in only 2.0 gallons of gas (25:1). While they call it "constant ratio oiling", it does vary a bit. And that's why I was reading the manual the other day trying to ascertain what Mercury claims it's supposed to run at - they don't really say other than for "breakin" to keep the engine speed below 3,000 for the first two hours and pre-mix at 50:1 WITH the oil injection operating.​

At any rate, I'd say that if you're in the 45:1 - 60:1 range on your pontoon, you got no problems with your oil injection. And if you're paranoid that it's not working, use Mercury's "breakin" recommendations and pre-mix at 50:1 until you get a good handle on how much the oil injection is actually injecting. All it's going to do is smoke a bit more until you use the pre-mix up.
--
Chris​

 

[chris.olson]

Re: Disabling the oil mixing system '83 40 Hp Mercury

At this time I'm able to find gas other than the 10% alcohol so I'm thinking my premix will mix like it's supposed to.

It depends on where you're at, as to what you get for fuel. In the midwest - Chicago area - here, the winter-blended fuels are terrible. I lost track of how many snowmobile engines I rebuilt for people this winter because of pre-mix problems.

These people will go to Farm & Fleet or Walmart and buy some cheap, generic two-stroke oil, mix it in a five gallon can and dump it in. Then they leave the sled set for two weeks with the tank half full. They start it up, take off down the trail and it smokes like a chain smoker for awhile, then goes lean and welds pistons right to the jugs. Then they come to me carrying a set of spark plugs with electrodes coated with melted aluminum and go, "Can you fix it for me?"
--
Chris​

 

[Rowroy]

Re: Disabling the oil mixing system '83 40 Hp Mercury

While I believe a person never stops learning, I do have a degree in mechanical engineering from the University of Minnesota and have worked on internal combustion recips most of my adult life - the vast majority of that time for Cummins on marine and stationary diesel applications. But never assume that I am stupid.​

I'm also intelligent enough to not have to degrade myself to personal attacks because my opinion doesn't agree with somebody else's. I would expect the same in return.
--
Chris​

I never alluded or assumed that you were stupid. I learned the A55-U-ME rule long ago. There is no need to take any of this personally and I certainly wouldn't personally attack another memeber of this board.

That's one of the problems with talking over the internet; things can be stated in one manner and taken in a completely different manner.