Johnson 90 hp. Oil injection system troubleshooting

[Katzinthehat1]

2000 Johnson o/b 90 hp running rough and smokes but not constantly. Occasionally runs well with intermittent sputtering. I replaced the fuel tank, fuel line with ball, added a water separator/ filter but still has roughness in idle and aforementioned ( thank God for auto spell,) sputtering. Before I pull the carbs I want to try disconnecting the oil injection and run on a 6 gal tank of premix high test/ 2 cycle oil at 50:1. That's what I was told all outboards ratio's are. So looking for a little guidance. I'm guessing I disconnect the wiring to the injection oil reservoir and pull the hose off and plug it or is taking wires off enough.

Any other tips for troubleshooting are greatly appreciated. Also I have been using quickkleen, stabil and sea foam regularly. One mechanic told me they don't even rebuild cards anymore just install new at ~$200 ea it's got 4 carbs

 

[Bosunsmate]

That sounds like a mechanic for the rich and for putting people off boating.
You should really do a compression test and spark test.
Also look at the plug colours, maybe only one is fouled so you can isolate it down.
In terms of disabling the oil, Ive never done it as ive never had one, ive always premixed but if you want to make sure the oil feed to the carb/manifold is not left open to suck in air as that dangerous

 

[racerone]

compression test needs to be done first.

 

[oldboat1]

After verifying compression, think I would check plugs. See if any are washed (water) -- and in any case, think I would dump the contents of the spin-on filter into a glass jar, and check for water and other contaminants. Running from that portable tank will be a clue as well (assume you have a permanent tank).

$200 for rebuilding a carb probably isn't awful, but think it shouldn't be difficult to tackle (satisfying too, once you get the hang of it). Might hold off reinstalling until you have rebuilt them all, as you might learn from the first one or two. Synchronizing might be tricky -- good to get hold of a manual.

Kind of a question of whether to run through ignition checks first, or start with carbs. With ignition, try to read the plugs first, then use an adjustable spark tester to see if you have strong spark.

[edit. BTW, in my opinion that dang seafoam just masks carb issues or makes them worse -- whatever the effect on decarbing the engine. Can't clean a carb without pulling it off, soaking everything metal, some careful picking and poking. Finish with some carb cleaner spray. I wouldn't do anything with the jets, other than soaking in place and blowing out with the carb spray.]

 

[Chris1956]

I do not see the utility of running a tank of premix. The OMS pump injects oil into the gasoline. If it inject too much oil the engine will still run fine, but smoke more. If it injected enough oil to foul a plug, it would fog the entire neighborhood, and you would know it.

BTW - carbs are rebuildable, and need to be cleaned every once in a while.

 

[jakedaawg]

A properly maintained four wire vro is a reliable unit. With that said...

Before you worry about switching to premix to test let's get through the basics.

1. Compression check. Report results
2. Open air gap spark check with a suitable tool set to 7/16". Check each cylinder. Report results.
3. Fuel sample into a clear container. We are looking for phase separation. Even if you just filled the tank from the gas station it needs to be checked. I can't tell you how many times a customer has come in with a fresh tank and we find this. Take the sample from the hose by squeezing the bulb and pressing in on the cowl end connector ball in socket.
4. Because you seem to suspect your oil injection do any running that you feel you need to with 50:1 premix in the tank. Double oil hurts nothing. As a mater of fact when in Comercial or race applications these same engines are spec by manufacturer to be run on double oil in many cases.