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Yamaha 70 hp 2 stroke outboard oil injection

Posted By: DWC

Yamaha 70 hp 2 stroke outboard oil injection - 09/05/22 09:42 PM

Recently got this motor, a 2001, and put a jet pump on it. It has an oil injection on it and i just topped it off yesterday before going out. I see there is a smaller tank on the right side of the main tank. I THINK there is oil in there from the looks of it, but i would have to remove some stuff to get to the cap for that. Ive read it is some sort of back up reservoir?? Was this manually filled or is this some kind of overflow from the main tank? I was looking at it today to verify it was using oil, and saw it looked several ounces down after burning 5 gallons of gas. Just making sure I wasnt supposed to be doing anything with this second tank.
Posted By: maintenanceguy

Re: Yamaha 70 hp 2 stroke outboard oil injection - 09/05/22 10:16 PM

Don't know what the little tank is for but if you weren't injecting oil and burned 5 gallons of gas - you would know.

A lot of guys don't trust the injection on older outboards and just mix gas so nothing goes wrong. Nothing sucks quite like having an outboard quit on your boat when you're miles away from civilization or the nearest boat ramp. I know.
Posted By: RustyShacklefrd

Re: Yamaha 70 hp 2 stroke outboard oil injection - 09/05/22 10:32 PM

It's a reserve oil injection tank I had one with it.
Posted By: DWC

Re: Yamaha 70 hp 2 stroke outboard oil injection - 09/05/22 10:52 PM

Anyone know how it gets filled? The cap isnt accessible easily so im guessing it gets filled off the main?
Posted By: RustyShacklefrd

Re: Yamaha 70 hp 2 stroke outboard oil injection - 09/05/22 11:42 PM

Mine was a 115 so a little different maybe but you could fill it from the top with the cap. The main oil tank was completely separate from the motor.
Posted By: jbyrd63

Re: Yamaha 70 hp 2 stroke outboard oil injection - 09/06/22 02:56 AM

Don’t touch it There is an oil pump that pumps from the main tank up to that one The engine mixes from the small one injected into the cylinder as it runs !
Posted By: jbyrd63

Re: Yamaha 70 hp 2 stroke outboard oil injection - 09/06/22 03:00 AM

Originally Posted by maintenanceguy
Don't know what the little tank is for but if you weren't injecting oil and burned 5 gallons of gas - you would know.

A lot of guys don't trust the injection on older outboards and just mix gas so nothing goes wrong. Nothing sucks quite like having an outboard quit on your boat when you're miles away from civilization or the nearest boat ramp. I know.


You have to get a kit to stop oil injections. If you put it in gas plus the engine is oiling it fouls then plugs quick .
Yamaha is one of the best leave it alone
Posted By: DWC

Re: Yamaha 70 hp 2 stroke outboard oil injection - 09/06/22 03:02 AM

Ya i hadnt planned on messing with it, just wasnt sure how it works. That makes sense though. Thanks.
Posted By: jbyrd63

Re: Yamaha 70 hp 2 stroke outboard oil injection - 09/06/22 03:08 AM

Any time! Enjoy it
Posted By: warrior

Re: Yamaha 70 hp 2 stroke outboard oil injection - 09/06/22 04:35 AM

The first generation OMC self oiling motors were the ones that had issues leading many to distrust and delete. But that got that fixed on later makes.

But it's left a common idea to delete and go back to premix.
Posted By: hippie

Re: Yamaha 70 hp 2 stroke outboard oil injection - 09/06/22 10:13 AM

I had a Yamaha snowmobile with oil injection back in the '80's and it was the cats meow. Worked great!
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