Your Opinion on Oil Injection

I just bought a 1995 Mercury XRi 200 hp with oil injection. I would like your opinion about leaving the oil injection in place or removing it and mixing the fuel and oil manually.

Re: Your Opinion on Oil Injection

leave it on, your motor, the environment and your wallet will thank you for it.

Re: Your Opinion on Oil Injection

Well most of the people I know including myself turf those oil injection units.
The thing will fail at some point and when they do, they take the powerheads with them.
Not so good for the wallet.

The other problem with them is that they are slow to respond. When you hammer down on the throttle, that is when the engines needs the most oil but it takes up to 15 seconds for the extra oil to make it to the carbs so for that time the engine is starving for oil right when it needs it the most and will wear out much quicker.

As far as the environment goes, all boating activities all combined since man began to run petrol on the water pales in comparision to the amount of oil that leaked from one of BP's wells this summer.

Re: Your Opinion on Oil Injection

Thanks for your opinion guys. I agree, however, with redjmp. It will fail sometime...I have known more than one or two guys that lost their powerhead when it happened. Just wanted a 2nd opinion. It is going to go. I don't mind premixing at all.

Re: Your Opinion on Oil Injection

hey, if you want to remove it fine, go ahead, might as well remove the starter too, just in case it fails, you can use a rope to start it, ditch the power trim as well, could go out at anytime you know, for that matter, dump the entire motor and buy some oars! how many people go down this road? no skin off my nose if you dump it, not too sure why you even asked, you had your mind made up already.

Re: Your Opinion on Oil Injection

rdh101 said:

Thanks for your opinion guys. I agree, however, with redjmp. It will fail sometime...I have known more than one or two guys that lost their powerhead when it happened. Just wanted a 2nd opinion. It is going to go. I don't mind premixing at all.

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The other problem with them is that they are slow to respond. When you hammer down on the throttle, that is when the engines needs the most oil but it take up to 15 seconds for the extra oil to make it to the carbs so for that time the engine is starving for oil right when it needs it the most and will wear out much quicker.

I totally disagee as anytime the throttle linkage is moved the pump ratio is changed. This is mixed in the fuel pump before it gets to carb so 15 seconds is out of the question. The 92 and up engines see less oil gear failures do to different design of oil gear. Usually a failure is due to a previous overheat or the plastic bushing swelling in crankcase and locking up shaft.

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Re: Your Opinion on Oil Injection

Faztbullet said:

I totally disagee as anytime the throttle linkage is moved the pump ratio is changed. This is mixed in the fuel pump before it gets to carb so 15 seconds is out of the question. The 92 and up engines see less oil gear failures do to different design of oil gear. Usually a failure is due to a previous overheat or the plastic bushing swelling in crankcase and locking up shaft.

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Well I have to admit that I am not familiar with the newer units.
Maybe they are more reliable/ efficient. But they WILL FAIL...eventually
Let us not forget our friend Murphy.
On a brand new motor granted it shouldn't break down right away, but on a 15 year old motor?

I wouldn't take the chance and all my boating buddies agree.

I have an '86 115 that came with an autoblender that had about 4 feet of fuel line between it and the motor.
For sure it would take quite a few seconds before the extra oil made its way down that length of line into the carbs and then it would only start to mix with the gas in there so another few seconds for the carbs to saturate with oil enriched gas before the cylinders finally saw the full amount of oil they needed.
By this time the boat is out of the hole and the load on the engine is reduced negating the need for so much extra oil but the damage is done by then.

Besides, is it any more work to pour oil into your gas tank than it is your oil resevoir?
Unless you have trouble with simple math and can't figure out how much oil to add...

This is the cheapest form of insurance imho.

And that is what the OP is asking for, Opinions. Well here is mine.

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Re: Your Opinion on Oil Injection

I have an 88 150 blackmax xr4.I disabled mine.No regrets.Piece of mind(as long as you dont forget to put oil in!).Todays oils pretty much mix instantly so no need to guess and put oil in first.And as for enviroment,A well tuned motor running premix will pollute NO MORE than any other motor,period.If it eases your mind,then do it.There really is no VALID arguement for not doing it.Hurts NOTHING.

Re: Your Opinion on Oil Injection

wrong!

Re: Your Opinion on Oil Injection

I would leave it working and give the Oil Injection system the proper maintanence at the schedualed time (re filters etc )

Re: Your Opinion on Oil Injection

I have an 88 mariner 150v that still has the oiling system connected,only problem ive had was the alarm module.

Re: Your Opinion on Oil Injection

noelm,"wrong!"? Could you specify what?was that directed at me?any FACTS?just curious

Re: Your Opinion on Oil Injection

well just explain to me how a motor running at 100:1 at idle will not use more oil = cost more, polute the environment more because of twice the oil, requires more maintenance because it is running far richer than the manufacturer designed, remember you mix at 50:1 for the motor all the time! I see those as facts, how long the fuel lines are has nothing to do with how much and when the oil is injected, another fact, the modern well maintained oils ystem is extremely reliable, yet another fact! and also reasons to leave the oil system on., but as I said, disconnect it if you like, it's your motor, the poster asked for opinions, we gave him opinions, but they differ, thats what it is all about!

Re: Your Opinion on Oil Injection

Remove it or you will be replacing the powerhead someday over it.Im all about the for sure thing and taking a gamble on it failing is to much of a worry for me. Mix the oil and gas and have no worries and enjoy the fishing.......

Re: Your Opinion on Oil Injection

I had an 89 merc with the AutoBlend and, yes, I junked it. Mixed my gas/oil myself. You people with the mid to late 80's motors. If they have the AutoBlend I'd pull them off and mix. However, I now have a 2001 75hp with oil injection and it's going to stay just the way it came.
Mike

Re: Your Opinion on Oil Injection

noelm said:

, how long the fuel lines are has nothing to do with how much and when the oil is injected,

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You are right the length has nothing to do with how much oil is blended and when, but it has everything to do with when that blend arrives in your cylinders. The fuel line runs from the tank to the autoblender where the correct mix is adjusted and then the mix must travel through the 4 feet of line , then it goes to the fuel connector, then another couple of feet of fuel lines and fuel pump then more fuel line before it reaches the carb.

At least that is the way my '86 motor came plumbed. Therefore sloooooowwwww to respond.

Re: Your Opinion on Oil Injection

redjmp said:

You are right the length has nothing to do with how much oil is blended and when, but it has everything to do with when that blend arrives in your cylinders. The fuel line runs from the tank to the autoblender where the correct mix is adjusted and then the mix must travel through the 4 feet of line , then it goes to the fuel connector, then another couple of feet of fuel lines and fuel pump then more fuel line before it reaches the carb.

At least that is the way my '86 motor came plumbed. Therefore sloooooowwwww to respond.

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I have no idea why your fuel lines are wrapped around the power head a couple of times, but I figure the engine is burning an ounce of fuel in 2 seconds at WOT, maybe 8 seconds at idle, and the 2 feet or so of 5/16 fuel line between the mixer and the carbs holds approximately 1/3 ounce of fuel. You do the math on the response. When you can it to WOT from idle, the right mix is getting to the carbs in 2/3 of 1 second.

I'm with the design engineers. The only reason to disable the oil system is economic. An old engine is not worth a 1000 buck split just to replace a nylon gear. Mix and go on with life.

With that in mind, one caveat. Be sure it's well maintained, and the oil alert module is working.

Re: Your Opinion on Oil Injection

j_martin said:

You do the math on the response. When you can it to WOT from idle, the right mix is getting to the carbs in 2/3 of 1 second.

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You are off your rocker dude! lol!!! Time to get schooled !!!

Ok lets do this the hard way...

Because I have a Navman tracker with a fuel computer, I know exactly how much I am burning for any given speed.

On my '86 I6 115, I get 2.45 km/l @ 44 km/h best cruise. @ 3150rpm
That drops to 1.4km/l @ 85 km/h @ 6000rpm

My auto blender was mounted inside the boat next to the battery so It is not unreasonable to need 4 feet of line from it to reach the motor is it? In fact it was probably closer to 5 feet.

So assuming 5/16" line, lets calculate the volume shall we?

Volume of a cylinder= pi times radius squared times length

Converting 5/16" to mm we get 7.9375 mm diameter.
Divide by 2 to get radius = 3.96875
Square that to get 15.75mm
Multiply by 3.14159... and you get 49.483

4 feet = ~1200mm so multply that and we get 59,380 cubic mm

1 liter = 1,000,000 cubic mm

Divide 59,380 by 1,000,000 and we get 0.05938 liters volume in 4 feet of fuel line.

Correct?

Maximum burn rate @ wot once at full speed = 1.4 km/l @6000 rpm@ 85km/h
Divide 85 by 1.4 to get 60.71 liters per hour at full speed /revs. Lets just say 60 shall we?

That is 1 liter per minute.
=0.0166667 liters/ second
Divide 0.05938 by 0.016667

= 3.56 seconds just to travel the 4 feet of line at maximum flow

However, the amount of fuel that flows is proportion to the rpm of the motor and does not flow near that rate if you hammer dowm from a 600 rpm idle.

If you like I could calculate out exactly how much fuel that is used for each revolution of the motor, but the point is that it idles around 600rpm and dropping the hammer only gets it revving only 2000 rpm or so until it is out of the hole so lets say 5 seconds or so before it starts to spool up.
So the burn rate at 2000 is 1/3 the rate at 6000.
At that rate, it takes over 10.5 seconds for the fuel to travel just from the autoblender to the fuel connection at the motor.

Once there it still has to travel about a foot to get to the fuel pump.
The fuel pump itself holds an amount of gas that has to be accounted for before we can move on down the line to get to the 3 carbs so at least another foot of lines and more like 2.
Now right there, that almost doubles the volume of the 4 foot chunk of line.

Now we get to the carbs and the volume of 3 float bowls.

It think it would be safe to say that the lines, pump and carbs on the motor itself hold more fuel than the 4' foot line I have calculated the volume for.

Are you starting to get the picture?

At full rate, it takes about 10 seconds for fuel to travel from the autoblend and reach the cylinders.

Hammering down from idle will take much longer.

15 seconds is not enough, now that I have really thought about it.
In reality it is more like 20 seconds.

Please explain why you feel the need to spew bullship out of your blowhole J martin.

Re: Your Opinion on Oil Injection

Great math and shows your point but the techicial side, most needle bearing 2 strokes need little if any oil at idle due to residues from WOT running. A little known fact was there were 2 type of Autoblends. The first used a harness to engine to get power and alarm and about 90:1 ration and the Autoblend II had built on alarm and used a battery and was a 70:1 ratio unit,thats why it still smoked at idle and a motor will run all day at WOT with less than a 50:1 ratio.

Re: Your Opinion on Oil Injection

If its an older motor and has oil injection switch it to mix in the gas! It's not worth it for an older motor to replace the powerhead. Replacing a starter doesnt cost that much as replacing a powerhead. If you can prevent from replacing a power head why wouldn't you do it!? It's easy to do and worth it. I can't even begin to tell you how many times I've heard. "Man I wish I would of done that," because of this.