Mercury oil injection operation question.

[waynelk]

Hello:
I just bought a 1989 XR4 150hp with oil injection. The tube that runs from the oil pump to the check T where it mixes with the gas is never filled solid with oil. Only oil in the bottom 1/4 of the tube. Is this normal at idle. Oil system works and adds oil but never fills the tube. Uses it as fast as it adds it. New to oil injection.
Thanks Wayne

 

[waynelk]

Re: Mercury oil injection operation question.

What no one knows if the line from the oil pump to the fuel t should be filled solid with oil? I'm going to guess yes and either the check spring in the T set for 2 lbs. is weak or too much restriction in fuel line from tank allowing the oil to be sucked out of the line overcoming the 2 lb. check. Shame no one knows the answer.

 

[chum1]

Re: Mercury oil injection operation question.

Yes it is a shame

 

[j_martin]

Re: Mercury oil injection operation question.

What no one knows if the line from the oil pump to the fuel t should be filled solid with oil? I'm going to guess yes and either the check spring in the T set for 2 lbs. is weak or too much restriction in fuel line from tank allowing the oil to be sucked out of the line overcoming the 2 lb. check. Shame no one knows the answer.

Sheesh, it's Sunday night. The world is to be at your beck and call at all times, eh.

Check a couple of things.
1. I believe the bleed procedure will burp the bubble out of the transfer line.
2. If that line leaks at either connection, especially the top one, it could suck in a bit of air. The fuel pump would normally hold a slight vacuum on that line.
3. Air intrusion into the fuel system before that T could possibly allow a bubble of air into the oil line. That T is not a check valve, just a mixing T.

The check valve is an air inlet check on the T on the starboard side of the engine, where the boat tank line comes in. It operates if the oil line from the boat becomes restricted, allowing air to enter the engine reserve tank, the oil system to continue operating for 1/2 hour, and the alarm to sound.

As it is, it's probably all right, but air intrusion into the suction side of the fuel system anywhere can eventually cause a lean condition and overheat damage.

Hope it helps,
John

 

[waynelk]

Re: Mercury oil injection operation question.

Thanks for the response. It's not an air bubble. I took the line off at the top, filled it with oil, Put it back together. started the motor. As it ran it sucked the oil out of the line down to about 1/4 full. Line is new, clamps are tight. I can see the oil dribbleing out of the oil pump so I know it's feeding oil. Running on premix for safety. Smoking like a son of a gun. So if that oil line from the oil pump to the t is supposed to be full at all times, and the t does not have a check, (I need to look into that. If no check when you pump the squeeze ball it would feed gas into the oil line?) Then the only solution is too much restriction on the gas feed line from the fuel tank? Easier to pull from the oil line than the fuel line? All I wanted to know was if the oil line to the t is supposed to be full solid at all times. Anyone with oil injection should know that. This is new to me. I'm replacing a 1973 1500 inline 6 without oil injection. All my other boats were inboards. Thank-you John for at least answering my question.
Wayne

 

[j_martin]

Re: Mercury oil injection operation question.

Thanks for the response. It's not an air bubble. I took the line off at the top, filled it with oil, Put it back together. started the motor. As it ran it sucked the oil out of the line down to about 1/4 full. Line is new, clamps are tight. I can see the oil dribbleing out of the oil pump so I know it's feeding oil. Running on premix for safety. Smoking like a son of a gun. So if that oil line from the oil pump to the t is supposed to be full at all times, and the t does not have a check, (I need to look into that. If no check when you pump the squeeze ball it would feed gas into the oil line?) Then the only solution is too much restriction on the gas feed line from the fuel tank? Easier to pull from the oil line than the fuel line? All I wanted to know was if the oil line to the t is supposed to be full solid at all times. Anyone with oil injection should know that. This is new to me. I'm replacing a 1973 1500 inline 6 without oil injection. All my other boats were inboards. Thank-you John for at least answering my question.
Wayne

Talk yourself into whatever you want. You haven't bled it right, or you have air intrusion somewhere, or both.

hope it helps
john

 

[hkeiner]

Re: Mercury oil injection operation question.

J_Martin has provided you with good information. The below link provides some additional information.

http://continuouswave.com/whaler/reference/mercuryOilInjection.html

The tube that runs from the oil pump to the check T where it mixes with the gas is never filled solid with oil.

I believe that the tube that runs from the oil pump to the check T on my 150hp is always solid with oil as far as I can tell, although I do not carefully monitor it.

 

[waynelk]

Re: Mercury oil injection operation question.

OK and I appreciate the help. I'm not trying to talk myself into anything. I am simply looking for a starting point. Now I know the oil line should be full. Also acording to the drawing #6, which is the T I am talking about is a "2-PSI CHECK VALVE--This valve prevents gasoline from being forced into the oil lines". I will go back and check for air intrusion from the oil reservoir to the T. All are new clear lines, and all have hose clamps instead of the wire ties. As I said I know nothing about Mercury's oil injection, but I do have some mechanical experience. Again thanks for the help. I am going to check into this further as time and weather permits. Last resort is to eliminate everything and go with pre-mix. That can be done with a $10 oil pump shaft plug and a couple other things.
Wayne

 

[j_martin]

Re: Mercury oil injection operation question.

OK and I appreciate the help. I'm not trying to talk myself into anything. I am simply looking for a starting point. Now I know the oil line should be full. Also acording to the drawing #6, which is the T I am talking about is a "2-PSI CHECK VALVE--This valve prevents gasoline from being forced into the oil lines". I will go back and check for air intrusion from the oil reservoir to the T. All are new clear lines, and all have hose clamps instead of the wire ties. As I said I know nothing about Mercury's oil injection, but I do have some mechanical experience. Again thanks for the help. I am going to check into this further as time and weather permits. Last resort is to eliminate everything and go with pre-mix. That can be done with a $10 oil pump shaft plug and a couple other things.
Wayne

on my XR4, the connection between the oil line and the fuel line is a T. On the parts diagram it is a T. The check valve is on the other side of the engine tank, between it and the boat tank, with a tail hanging down through which to draw air from atmosphere.

Perhaps someone put a check valve where the T should be, and that is the problem.

Under normal conditions, the oil pump will not allow enough fuel to back up through it to need a check valve. You are not supposed to run it with a pressurized fuel supply without special considerations, and the safety circuit would do the same thing, shut off fuel pressure when the engine is not running or cranking. Oil pressure from the boat supply tank is supposed to go to 0 in a few minutes after shutdown. Sometimes the check valve (crankcase, lower forward starboard side) will fail to do that, and excess oil gets forced into the fuel during shutdown. I've never heard of fuel getting forced into the oil system.

Don't be so quick to junk a good system.

hope it helps
john

 

[PrinceValium]

Re: Mercury oil injection operation question.

OK and I appreciate the help. I'm not trying to talk myself into anything. I am simply looking for a starting point. Now I know the oil line should be full. Also acording to the drawing #6, which is the T I am talking about is a "2-PSI CHECK VALVE--This valve prevents gasoline from being forced into the oil lines". I will go back and check for air intrusion from the oil reservoir to the T. All are new clear lines, and all have hose clamps instead of the wire ties. As I said I know nothing about Mercury's oil injection, but I do have some mechanical experience. Again thanks for the help. I am going to check into this further as time and weather permits. Last resort is to eliminate everything and go with pre-mix. That can be done with a $10 oil pump shaft plug and a couple other things.
Wayne

If it was me I would MUCH rather have a motor that mixes the oil like that than premixing in the tank.

 

[waynelk]

Re: Mercury oil injection operation question.

On the parts diagram for the XR4 it is a $40 T which is why I was thinking it is more than just a T. I'll take it off and check it out though, along with looking for an air leak somewhere. I would rather have oil injection but not at the cost of ruining my motor. It is not all that hard to premix. Been doing it for years. Only drawback is a little more smoke at idle. I can live with that having peace of mind knowing I have plenty of lubrication to the motor. That is a last resort. This system seems simple enough and now that I have some idea of what to look for I am going to try to figure out what the problem is. Thanks again for the help.

 

[j_martin]

Re: Mercury oil injection operation question.

You must have the late XR4. It's called a fitting, albeit a non-standard one.

At my age, oil injection is a lot more reliable than me.

1. The bubble is probably of little consequence.

2. If you bleed it down, and the bubble reappears, it's an air leak.
Possible sources:
a. Regular zip ties are not the same as the zip tie style hose clamp. Use the proper clamps, or use Hellerman snapper clamps.
b. Might be a pinched 0-ring in the oil pump itself, especially if someone's tinkered with it.
c. To see if it could be air intrusion into the fuel system, temporarily replace the fuel line between the bayonet connector and the mixing T with a piece of clear vinyl tubing (hardware store junk) and watch it.

hope it helps.
John

 

[waynelk]

Re: Mercury oil injection operation question.

Thanks John: I used regular metal hose clamps. I also have a clear plastic line on the feed for the gas to the t. My XR4 is a 1989. (First year I think) I don't think anyone tinkered with it as the boat was totalled after a few years and the motor was stored for 15 years. (Reason I bought it) Looks like new, except the bent prop shaft. I'll look into an air leak as that makes the most sense. It still feeds oil so it would work but I would rather it injected the oil than sucked the oil. I'll try a few things and see what happens.
Wayne

 

[hkeiner]

Re: Mercury oil injection operation question.

The check valve is on the other side of the engine tank, between it and the boat tank, with a tail hanging down through which to draw air from atmosphere.

Perhaps someone put a check valve where the T should be, and that is the problem.

Under normal conditions, the oil pump will not allow enough fuel to back up through it to need a check valve.

I just thought I would clarify that there are three check valves on the oil injection system.

- One check valve is screwed in to the crankcase and feeds pressurized air to the remote oil tank.
- The second check valve is on the starboard side of the motor and it's purpose is to allow air in to the oil line in the unlikely case that vacuum were to occur in the oil line between the remote oil tank and the reservoir oil tank under the cowel.
- The third check valve is the one between the oil pump and the T and its purpose is to keep gas from being pushed up towards the oil pump when the fuel bulb is squeezed. The oil pump is more of a metering device than a high pressure inducing pump.

 

[j_martin]

Re: Mercury oil injection operation question.

Thanks John: I used regular metal hose clamps. I also have a clear plastic line on the feed for the gas to the t. My XR4 is a 1989. (First year I think) I don't think anyone tinkered with it as the boat was totalled after a few years and the motor was stored for 15 years. (Reason I bought it) Looks like new, except the bent prop shaft. I'll look into an air leak as that makes the most sense. It still feeds oil so it would work but I would rather it injected the oil than sucked the oil. I'll try a few things and see what happens.
Wayne

If you're talking about a worm gear, spiral slot band clamp, likely that's your problem. They don't work real well with the small plastic fuel and oil lines.

The zip style clamps, not regular zip ties, work OK. The snapper clamps are excellent, reusable, and very easy to apply. Believe it or not, the spring clamps, either band or wire, work better than worm clamps.

I don't know exactly what's in the oil pump, but it will operate with positive pressure or vacuum at the inlet, so it is a pump. On a 1988 engine, the mixing fitting is just a T, and it works fine. I have no experience with the later one, but if it's a valve, I suspect it holds back the oil at a little over 2 lbs pressure to prevent pressure on the system when stopped (an abnormal condition) from forcing oil into the fuel lines, causing hard starting and the dreaded smoking at startup. In other words, I expect it's an engineering fix to compensate for a poor crankcase pressure check valve known to fail too frequently, instead of fixing the poor valve design. For your problem, it shouldn't make any difference if it works at all.

hope it helps
john

 

[waynelk]

Re: Mercury oil injection operation question.

Just to update where I'm at. I took the T off and on my 1989 XR4 there is a spring loaded check where the oil line comes in. Still has original hoses and the wire tie clamps so I'm guessing it's original. I am using small worm gear style hose clamps so I may look into something else. Changing all fuel and oil lines as I go. Been raining here and about 50 deg. so it may be a couple days before I get any further. New check T seems like stronger spring than old so not sure if it will help but it wouldn't hurt. Never liked the spring wire clamps but have some fuel injection hose clamps. Oil hoses I'm using are clear 1/4" ID fuel line hoses I use on my motorcycle. Not sure where to get the toothed snapper clamps that small. Mercury dealer maybe? I'm going to concentrate on John's theory that it is an air leak from somewhere. I do agree on the oil pump. It has a 2 psi spring loaded relief valve and the oil metering barrel works by pushing on the valve to let more or less oil through. Thanks to you guys I feel like I'm making progress. Nice warm day and no rain and I'm thinking I can figure something out.
Wayne

 

[j_martin]

Re: Mercury oil injection operation question.

FI clamps would be fine, if not overkill. Forgot about them.

Snapper clamps can be had at mcmaster.com. Search term "snap grip clamps"

Tygon fuel line works well except for the pulse hose on the fuel pump. That one has to have some beef to it. Tygon soaks up the crankcase pulse energy and fails to deliver it to the pump. (experience talking)

 

[waynelk]

Re: Mercury oil injection operation question.

Thanks John. Overkill is always better than underkill right. I believe the clear tubing I use is polyurethane. Tygon is food grade and gets mushy soft with gasoline or heat. Clamps also crush right through it. The hose from the T to the fuel pump and the pump to the carbs is neoprene with a clear cleanable glass strainer inline. Also have the mercruiser spin on water seperator/fuel filter in the main line from the tank. May get a chance tomorrow to try a couple things and see where I'm at. Again thanks for your help. You seem to know a bit about these outboards and I appreciate your sharing what you know. I'm wishing I had stuck with my 4 cycle, no smoke, no noise, fuel efficient Inboard/outboards. These outboards are smokey, noisy, gas hogs. Not looking to spend $15,000 for a big heavy 4 stroke yet though. That's my wifes plan. For that much I could pay someone to take me fishing the dozen times a year I get to go.

 

[waynelk]

Re: Mercury oil injection operation question.

PROBLEM SOLVED. Thanks to all who helped, especially John. Turned out to be a problem with the oil pump. Pumping but not steady. Top cover of the pump houses a barrel and spring which pushes down on the "piston". Bottom cover is the throttling shaft which is a cam. Middle is the piston which is spinning in the bore. Bottom of piston has 2 half moon slots which with the cam controls how far the piston drops. (Further it drops the more oil it pumps.) Simple design. I'm guessing mine wasn't dropping every time therefore feeding oil but not enough steadily. Working good now, tube to mixing T stays full of oil. Just wanted to update in case anyone else runs into this problem. One final question. The poppet valves on the XR4 V/6 used for cooling at speed. Where would I find these to make sure they are clean. Thanks again to all. Appreciate your willingness to help out.
Wayne

 

[DamianJP]

Re: Mercury oil injection operation question.

Hey waynelk

The poppit is located under the switch boxes. Gonna be a sideways figure 8 looking thing. One small circle and one big circle plate with a little vent hole in it.
Should be 4 bolts. Lemme know when ya find it and if ya need help with it.



Thanks,
DamianJP