Oil injection or pre-mix

[Down South]

Hello guys,<br />I was just wanting a few opinions on oil injection versus disconnecting the oil pump and going with pre-mix. <br /> I hear different opinions about which is best overall. Some people say disconnect the oil pump because of potential problems that the pump can cause and some folks say (never had a problem). I've ran oil injection for years and never had a problem myself. Of course I've never let my oil tank run dry either. I always make sure it's topped off every time I fuel up.<br /> Anyway will going with pre-mix affect the motors preformance? (I know that these questions are generalized because I'm not asking about a specific brand, year model, or horse power motor). <br />I know pre-mix would be safer as far as oil pump failure is concerned, but what's the chances on an oil pump failure. <br /><br />If you have had problems with oil injection, let me know. I'd like to know the specifics of the problem too.<br /><br />Anyway, it's something to think about.

 

[Beernutz]

Re: Oil injection or pre-mix

The answer to your question would be brand-specific.

 

[sandman]

Re: Oil injection or pre-mix

I personally know two people that lost great engines due to oil pumps failure (oil injected). All the local wrenches I know recommend disconnecting and mixing. I disconnected mine, and would also disconnect my Yamaha jet ski if I knew how.

 

[12Footer]

Re: Oil injection or pre-mix

As Beernutz (gotta love that handle) says, brand specific. OMC, I would disconnect under warantee (if it were on my boat). Merc's??<br />Suzuki???<br />Yamaha, I never heard of a pump failure.<br />Some cannot be disconnected without affecting performance, due to fuel injectors' ability to atomize the mix. But that's just me being a parrot,having read about it.

 

[Down South]

Re: Oil injection or pre-mix

I do have a 94 Johnson 200 that I was thinking about disconnecting the oil injection pump on. I was being general in my first post cause I have several motors. One is a smaller Yamaha, 25 HP. It's a great little motor. I've had it for I guess 8 or 10 years now. For some reason I trust the oil pump on it. I also have a Merc 90 HP that had the oil injection pump disconnected when I bought it. <br /><br />But back to the Johnson 200. It's a 94 model. What do you fellows think about it? disconnect and pre-mix or leave it hooked up.

 

[R.Harris]

Re: Oil injection or pre-mix

I have rebuilt 7 or 8 engines with oil injection. Not so much the pump being the culprit but the oil lines themselves drying out and cracking or breaking as it leaves the pump. The alarms never sounded since oil was still being pumped until it was to late. I try to recommend to my customers that they should do a visual check on their oil and fuel lines for any signs of leakage or deterioration occasionally. A few minutes looking under the cowling every now and then can save a lot of headache and money in the long run.<br /><br /> Several wrenches I have talked to say oil injection is great while the motor is under warranty,but after that if it were theirs they would do away with it.

 

[Beernutz]

Re: Oil injection or pre-mix

Be really careful with this one, guys! It all depends upon where the oil is "injected" into the motor. If it's a Johnson or pre-FICHT Evinrude, the oil is mixed with the fuel before it enters the carburetor floatbowl. On these engines, elimination of the oil pump circuit will cause no problems with performance or longevity, because the carburetors are jetted for the mixture. If the oil is injected anywhere between the carb and combustion chamber, you will end up with a "lean" condition that jeopardizes pistons. As I have explained previously, a carb jet will only deliver a finite volume of liquid. If you dilute that liquid with oil, less of the solution arriving at the combustion chamber will be fuel. It is the air:fuel ratio that determines the temperature of combustion. That's why adding more oil than recommended to pre-mix can actually damage an engine that is run anywhere near WOT for extended periods. You say it only amounts to a couple of percentage points in the solution? You're right. But believe me, at 90 ignitions per second, each combustion chamber knows the difference!<br /><br />I don't think I'd mess with the pump on any of the fuel injected motors. With fuel being injected directly from the tank to the combustion chamber, they use alternative methods of getting the lubrication to the lower end in the crankcase. If you eliminate the pump in these engines, you'll fry the bottom end pronto!<br /><br />But, really guys. Brand loyalties aside, we all know who's oil pump we're worried about.<br />But I've been running Johnsons for many years, and have never experienced a pump failure. (Hope I haven't jinxed myself here) My neighbor, however, with a motor identical to mine, had a complete failure and seizure last year. His "no oil" alarm never sounded. It did kick into "SLOW" mode, though. Still, with no oil, the damage was done. <br /><br />Check your owner's manual. OMC's describes the proceedure for eliminating the oil pump from the circuit, and actually provides the plug and cap to do the job. Do they know something that they're not telling us?

 

[Down South]

Re: Oil injection or pre-mix

Great answers guys. This is what I was looking for. I was pretty sure I could eliminate the oil injection on my Johnson and I figured any motor that injects past the carbs, it would be a preformance problem or worse. I hear a lot about disconnecting the oil injection and folks need to know which motors are safe to do so on. <br /><br />Any more replys to this first post would be appreciated.

 

[FNG]

Re: Oil injection or pre-mix

Well as I know a couple of you guys have been following my issues with my Ficht 150. With my most recent issue this past weekend with an oil problem I learned some stuff.<br />If you have a Ficht engine you can not disconnect the oil injectors. Only a very small amount of oil actually gets mixed with fuel. Most of the lubrication is injected into the Piston on each cylinder. Disconnection of the auto lube and pre-mix of fuel will clog the fuel injectors that are not designed to deliver an oil mix along with damage to the combustion chamber due to lack of direct oil injection. Now thats for an Evinrude Ficht engine. They told me if I had the Johnson Carb. engine you can get way with disconnecting the auto lube system.<br /><br />FYI it appears that I got stuck out at sea for 7 hours due to a sensor on the Ficht injector. My engine had all the oil it needed...It just didn't think it did. End result, I was still stuck. The good thing, if you can find any good out of it, my engine is fine.

 

[Olson]

Re: Oil injection or pre-mix

Down South,<br />I have a friend that seized the block of his 200 HP Yamaha outboard. Oil pumped stopped working and no alarm sounded. No warning. Too late. <br />I was at a party several days ago and a guy told me that his friend also seized up twin 200 HP outboard engines that were fairly new due to oil injection failure.<br />Pick your option that gives you peace of mind.

 

[Beernutz]

Re: Oil injection or pre-mix

For the sake of reliability, I prefer stone-axe simplicity. That's why I stick with carbureted engines and have thus far avoided fuel injection. I mean, it ain't like we can get out and walk! A 7 hr. delay in your return isn't my idea of fun, either. Now, if that lower unit will just hold together. Right, FNG?

 

[Down South]

Re: Oil injection or pre-mix

Back to the top for the last time to see if I can get a few more replys on this subject, then off to my camp for a week of fishing and of course work on the camp.

 

[beatstheshore]

Re: Oil injection or pre-mix

FNG, do you live in overland park, ks? My neighbor two doors down has a 150 ficht (2001 I believe) that he just bought new on a Lowe deck boat. He had an engine failure 2 weeks ago with 3 hours on the engine. I don't know the cause. It would seem lubrication related, though with that few of hours. They totalled the engine. Can you say upgrade?

 

[my new fishmaster]

Re: Oil injection or pre-mix

My 89 80hp merc fuel pump had some problems, the rubber valve that lets the gas come in was folded over. The problem was no gas just oil so it over lubed her.

 

[Down South]

Re: Oil injection or pre-mix

Well, back to the top one more time.