1992 Yammie 225 unburned oil, is this normal? - The Hull Truth

Leatherhead · 05-23-2009, 10:18 PM

This motor's got 800 hrs on it and has been bullet proof for the 5 yrs I've had it. Recently it started wet fouling plugs and passing unburned oil. I found a bad fuel pump, and replaced them both. Also removed and cleaned the carb jets, three of the six high speed jets were gunked up one of the idle jets had some gunk on it. None had been cleaned in the last 5 yrs. Motor now runs fine on the hose, but in 5 min. of idling it'll turn a bucket black with unburned oil. Does this sound right? I'm considering a decarb now... Appreciate any comments.

I've been reading awhile on this site, first post here. Looks like a great site with alot of knowledgeable people on it. I'm no outboard expert, and appreciate any help you guys can give!

A1 Outboard · 05-24-2009, 12:07 PM

You should have a qualified tech check the oil pump adjustment. When the carbs are cleaned this adjustment along with carb sync and link needs to be done. It is normal for these engines to pass a small amount of raw fuel and oil at idle. Another area that could cause this problem is the cold engine fuel enrichment system.

Leatherhead · 05-24-2009, 12:43 PM

A1, thanks for the reply. I cleaned the carb jets, but didn't pull the carbs apart to do the internals. Now I'm wondering if I should have. I did spray some carb cleaner down each barrel. Should I expect to see some oil on the plugs after idling even when it's correctly adjusted and running or should they all be dry?

Leatherhead · 05-25-2009, 11:47 AM

This plot shows the change in efficiency across the operating range, is 15 to 25% worse than the baseline about 4 yrs ago. Used fuel flow meter for testing. Fortunately had run a baseline years ago when the motor was in good running order. The blue data points are the new ones from today.

A1 Outboard · 05-26-2009, 05:17 AM

With this many hours on the engine you need to run a internal engine cleaner through the carbs. Plugs should be dry with a small amount of oil on the outer shell. Look to see if the oil pump link is connected or damaged. It is possible that you have some leakage past the needle and seat assemblies causing your problem.

Leatherhead · 07-08-2009, 07:10 PM

As an update, I've tracked down the cause of the unburned oil. Had a bad idle inrichment pump diaphram, found it had a hole in it. Motor is back running normally. Now I've got a fuel supply problem. I can't seem to get more than about 9 GPH flowrate at WOT. I've got a fuel flow instrument inline, and just cleaned the upstream filter I figure I've got a partially blocked fuel tank uptake. I'm abit stumped as to how to remove it. Has a cutoff valve that has to come off in order to remove the fuel line. How do you remove it?

A1 Outboard · 07-09-2009, 04:49 AM

I'm puzzled by your terminology. There is a filter on the fuel inlet in the boat tank. There should also be a water separator in line. The fuel tank will have an antisyphon valve. Your engine should only run at 1/2 throttle with 9gph. If it runs 5-6000 rpm the problem may be with the flowmeter. Your dealer should run a vacuum and pressure test on the fuel system to find if you have a problem.