oil injection- yes/no

airsnoopy

Recruit
Joined
Jul 20, 2009
Messages
1
I just purchased a 2004 Johnson 90 hp, the oil injection had been blocked and they were pre-mixing oil/gas.. I know this is a common practise.. Does the oil lubercate anything or just mix with the gas.. Seems like a lot of enginering to just block it off..
 

ryendube

Petty Officer 1st Class
Joined
Jul 7, 2009
Messages
200
Re: oil injection- yes/no

the mix is the lubrication. so umm no?
 

d.boat

Chief Petty Officer
Joined
Sep 19, 2008
Messages
520
Re: oil injection- yes/no

I just purchased a 2004 Johnson 90 hp, the oil injection had been blocked and they were pre-mixing oil/gas.. I know this is a common practise.. Does the oil lubercate anything or just mix with the gas.. Seems like a lot of enginering to just block it off..

in a 2 stroke (AKA 2 cycle) engine, the oil mixes with the gasoline and lubricates the entire engine while it's running. (except for the gear box in the lower unit). This is different than how a 4 stroke engine works - they have an oil reservior and an oil pump that circulates the oil.

There's a good simple explanation of the difference in a website called "how stuff works" http://science.howstuffworks.com/two-stroke.htm

The way the oil gets mixed with gas in a 2 stroke is either through "premixing" the oil and gas in the gas tank or through an oil mixing fuel pump system. In those systems, the oil is held in as separate tank from the (unmixed) gas, and then mixed automatically before it is sent to the carberators. Here's how the Johnson/Evinrude system (AKA "VRO" or "OMS") works:

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

A lot of people have a strong bias against any automatic oil mixing system. I have just switched to one from premixing for many years and I prefer it so far. The risk with the automatic system is that the system will fail to oil and that the alarms won't warn you that it's failing. The risk with the premixing system - in my experience - is that humans are fallable and will forget to add oil, add an insufficient amount, or add too much.

Neither risk is great and it just depends on whether you trust the technology or yourself more!

You can convert your system back and the cost and effort will depend on what parts you have (or which were removed), and the condition of the parts.

I just bought a used tank and lines on ebay for less than $50 and a brand new current pump for $300. I did so to update a 19 year old system for peace of mind, but it was still working fine. All my alarms and circuits are intact, so I don't ahve any additional costs.
 

R.Johnson

Rear Admiral
Joined
Sep 24, 2003
Messages
4,446
Re: oil injection- yes/no

Oil, pushed into the fuel will mix. When pulled into the intake of the engine, and swirled around, will it stay mixed? Tell me from your experiece here.
 
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