1995 40hp Mercury Oil injection

[Bigtimber]

I've done alot of searches here but unable to come up with the answers I need...any help would be greatly appricated. I have a 1995 40hp mercury 4 cylinder...I want to bypass the oil injector system. Oil line comes from oil tank to intake side of " oil pump" ...then to fuel line with a tee fitting. Once you route the premixed gas line around that to fuel pump......What exactly to do with injector pump? Loop it?? Let it run dry? Plug or cap both hoses? Or take pump out and remove a gear or shaft? Really could use some help here to do the right thing with this model...my new little rig means alot to me. I just simply don't trust a pump to add the oil and I don't mind mixing the gas one bit. MANY thanks in advance

 

[Bigtimber]

Re: 1995 40hp Mercury Oil injection

Anyone? :redface:

 

[henrye718]

Re: 1995 40hp Mercury Oil injection

Bump

 

[chris.olson]

Re: 1995 40hp Mercury Oil injection

I've done alot of searches here but unable to come up with the answers I need...any help would be greatly appricated. I have a 1995 40hp mercury 4 cylinder...I want to bypass the oil injector system.

The best thing to do would be leave the oil injection system operational. I've never seen one fail on that series of engine. The older Black Max's - yeah - but not these. You're more likely to experience engine damage from pre-mixing; mixing the wrong ratio, someone adding gas and forgetting to mix at all, or using a petroleum-based oil that doesn't mix properly with ethanol-containing fuel (just about all modern gasolines have up to 10% ethanol added as an oxygenate). If you use a petroleum-based oil in ethanol-containing fuel, it seperates after sitting a couple weeks and starves the engine on oil because you neglected to shake up the tank.​

That being said, the best way to bypass the oil injection system on a 40 is to put a recirulation line on the pump, making sure the pump and line has oil in it, then remove the injection check valve "tee" assembly from the fuel line. And make sure to use a synthetic oil that will mix with ethanol in a pre-mix system. There is no petroleum based two-stroke oil that will mix with ethanol, and I've lost track of how many snowmobile engines I've fixed for people in the last 5 years because they tried it. They come dragging the sled into the shop with the pistons welded to the bores and can't figure out why. The same thing will happen in a two-stroke outboard.
--
Chris​

 

[Bigtimber]

Re: 1995 40hp Mercury Oil injection

The best thing to do would be leave the oil injection system operational. I've never seen one fail on that series of engine. The older Black Max's - yeah - but not these. You're more likely to experience engine damage from pre-mixing; mixing the wrong ratio, someone adding gas and forgetting to mix at all, or using a petroleum-based oil that doesn't mix properly with ethanol-containing fuel (just about all modern gasolines have up to 10% ethanol added as an oxygenate). If you use a petroleum-based oil in ethanol-containing fuel, it seperates after sitting a couple weeks and starves the engine on oil because you neglected to shake up the tank.​

That being said, the best way to bypass the oil injection system on a 40 is to put a recirulation line on the pump, making sure the pump and line has oil in it, then remove the injection check valve "tee" assembly from the fuel line. And make sure to use a synthetic oil that will mix with ethanol in a pre-mix system. There is no petroleum based two-stroke oil that will mix with ethanol, and I've lost track of how many snowmobile engines I've fixed for people in the last 5 years because they tried it. They come dragging the sled into the shop with the pistons welded to the bores and can't figure out why. The same thing will happen in a two-stroke outboard.
--
Chris​

Thanks for the advice!!...I will be the only one at fault for not premixing (no one else better mess with it ...and the synthetic oil advice..thanks I'll stick with that then . When you say a recirculation line...what EXACTLY do you mean? Simply loop it back into itself? Would that not build pressure on itself? OR maybe I'm not thinking right...wouldn't be the first time . THANKS for the reply

 

[Bigtimber]

Re: 1995 40hp Mercury Oil injection

Bump

 

[chris.olson]

Re: 1995 40hp Mercury Oil injection

Simply loop it back into itself? Would that not build pressure on itself?

Sorry I didn't get back sooner. Yes-put a recirculation line on the pump by connecting a short piece of hose to the inlet and oulet ports. You can hook up the hose to the inlet of the pump, then with a small shringe filled with oil, inject a little oil slowly into the hose, letting the air out, until it's full. Then quickly connect the other end of the hose to the outlet of the pump.​

It won't build pressure on itself because it's a positive-displacement pump. Whatever displacement is generated on the inlet side is duplicated on the outlet side with each stroke of the pump piston.​

You need to put the recirculation line on it because the pump needs oil or it will eventually seize. I suppose you could make a blockoff plate and remove the pump, but keep in mind that if you do that you change the volume of the crankcase for the bottom two cylinders unless you make a pump-eliminator blockoff with EXACTLY the same volume as the oil pump and gear. Increasing the volume of the crankcase will cause the bottom two cylinders to go lean and burn them up.​

Mercury makes a block-off for the Black Max engines, but I'm not aware of one for the 40.
--
Chris​

 

[Tregaskis]

Re: 1995 40hp Mercury Oil injection

Thank you for this advice. I have a 1994 4 cyliner Merc Tracker on a pontoon boat and the oil injection system works great. I WAS going to ask if the pump on this motor is gear driven and if the gear is plastic like on some of the early oil-injected Black Max's. I am thinking you answered my question and I will not worry about the pump any more. Thanks Greg in Redding, Ca

​

Sorry I didn't get back sooner. Yes-put a recirculation line on the pump by connecting a short piece of hose to the inlet and oulet ports. You can hook up the hose to the inlet of the pump, then with a small shringe filled with oil, inject a little oil slowly into the hose, letting the air out, until it's full. Then quickly connect the other end of the hose to the outlet of the pump.​

It won't build pressure on itself because it's a positive-displacement pump. Whatever displacement is generated on the inlet side is duplicated on the outlet side with each stroke of the pump piston.​

You need to put the recirculation line on it because the pump needs oil or it will eventually seize. I suppose you could make a blockoff plate and remove the pump, but keep in mind that if you do that you change the volume of the crankcase for the bottom two cylinders unless you make a pump-eliminator blockoff with EXACTLY the same volume as the oil pump and gear. Increasing the volume of the crankcase will cause the bottom two cylinders to go lean and burn them up.​

Mercury makes a block-off for the Black Max engines, but I'm not aware of one for the 40.
--
Chris​

 

[Texasmark]

Re: 1995 40hp Mercury Oil injection

I just removed the pump function from my 90 hp triple. I removed a hose and 2 screws pulling the pump top off, took out the gear which included a slotted end shaft and put the rest back together. Changed nothing else. Left the oil in my tank so that my oil alarm wouldn't scream at me if I drained it. Course I could disconnect my oil alarm wire but I didn't.

On forgetting to fill, I wrote it on the boat adjacent to the fuel inlet to add oil. Ha. If I forget after that I deserve the consequences. Only difference I notice is that since you run 50:1 all the time it smokes a little more at idle especially before the engine warms up because you are running a richer mix...pump put out like 80:1 at low speeds as I recall.

Mark

 

[Daneo]

Hey Chris I'm at the crossroads also if I should disable the oil injection on my 93 Merc 40 4 cyl. I thought removing the plastic gear off of the oil pump and bolting it back on would be all it took and then wouldn't need a loop line. Could you talk more about what you mentioned earlier about "using a blockoff with EXACTLY the same volume as the oil pump and gear. Increasing the volume of the crankcase will cause the bottom two cylinders to go lean and burn them up."
Also when there is sufficient oil in the oil tank there should be no continuity between the blue oil sensor leads when measuring with a meter.
Happy boating! Dane