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Deja vu I know..... but milky oil on 2006 Nissan 9.8hp 4 stroke

Jupiter Dinghy

Jupiter Dinghy

Regular Contributor
There have been quite a few threads here and elsewhere, reporting that milky oil issue on almost new motors, (9.8hp 4 stroke) but none ever reported what the final findings and.or resolution was.... the closest one to doing it was this one:2017 9.8 4 stroke with water in the oil after 10 hours of breakin (marineengine.com) mentioning "gunk on oil pick up tube".
Where is the oil pick up tube? Has anyone else made any findings on this.
For the record, my motor has very low hours, look brand spanking new under the cover, a mechanic replaced all the power gaskets, including head, and took it to a machine shop where the block was deeemed in good shape (not sure what they did ot what that means).
Any input appreciated, thanks.
 
All 4 st OBs of all manufacturers tend to make oil. That's because the crankcase runs unusually cool. The issue is exacerbated by running oil that is too heavy, or synthetic oil, or prolonged idling, or running in cold water. In some cases, this will be great enough accumulation to make the oil milky. If the power head gets really wet (as in a kicker that should have been raised, but wasn't at high speeds, they can even ingest water through the intake or breather.
 
Thanks Paul, in my case it is a 2006 NSF9.8A3, which as I mentioned in first post harldy shows any sign of use.
I did 3 consecutive oil changes, with a 5mns run between each, and after last change, the oil looks fine. (What came out at 1st and 2d oil change was really watery).

I will go test it under load on the inflatable dinghy this weekend, checking the oil periodically, and ass if it gets milky again...
 
One of my favorite motors, that rugged 9.8. When you say watery, I hope you don't mean really thin. If so, a ruptured fuel pump can dump gas in the oil. If it was just water, then regardless of age, it may need to be run really hard for 5 or 10 hours to seat the rings. I have seen several 10 YO motors that were babied, and never really seated the rings. Good luck.
 
Thanks again.
No gas, just water giving the oil that white color. And the way this motor purrs (like a new one would) kinda makes me want to cross off the ruptured fuel pump scenario.

Starts first pull, revs up quick and idles perfectly.
I will go and give it some wot time as you suggest (the only thing making any sense at this point).
 
Update: Took the dinghy out yesterday, good news and bad news. The good news is after running for about an hour, no trace of water in oil. Looks as clean as when it came out of the bottle. Bad news is I could only run it for an hour because it was acting up.
Fired right up at the ramp, headed out towards the full speed area, and after about 1/4 mile, the motor quit. Started back up but would die again if I tried opening the throttle some. So I turned around and putted back idle towards the ramp, ready to call it a day, and when I got at the ramp, it started accepting to rev up again, so went back out again thinking I always can paddle my way back in the worst case scenario. Got to the full throttle area and opened wide, no problem, except when I rolled the throttle back to turn around, it stalled. Started back up, was a bit hesitating when revving up, but but got me back to full throttle again. The problem reoccurred a few times (stalling when going from wot to idle) but always restarted, until that one (and last) time when it didn't, so out come the oars, and I head back to the ramp paddling.
Take the boat out of the water and once on trailer and ready to go back home, I thought I'd check the oil, it looked perfect, so I was at least happy about that part, and just for the hell of it, I give the starter rope a pull, and of course it fired right up and purred like a kitten.
Back home, I hooked the ear muffs and fired it up again (at first pull), and was sounding absolutely perfect, revving up with no hesitation....
So I'm thinking (correct me if I'm wrong) that the carb needs a good clean up as there seems to be some kind of restriction somewhere between idle and wot.
I'll do that and try again, hopefully for a few hours that time, as originally planned, and see if my oil issue is in fact no longer existing.
 
Time for an update: I pulled the carb for a thorough cleaning, put it back on, the motor fired right up ran and idled great, but I saw fuel leaking from the bottom of the carb (while running perfectly mind you)....???
I pulled the fuel line to stop the fuel supply and the leakage stopped almost immediately, so I ran all the fuel out of the carb until it stalled (which takes an amazingly long time on these things), pulled the carb out again, double checked everything including float adjustment, made sure everything was tight, and put it back on. Same thing happened. What am I missing? The motor starts and runs awesome, but as soon as the fuel supply is on, it leaks from the bottom of carb into the lower cowling.
BTW, the needle valve looks absolutely perfect (and that leak didn't exist until I pulled the carb so I'm guessing I messed up somewhere but can't figure out where).
 
Has to be a needle/seat issue. Invert the carb and verify nothing can go through the needle/seat. Since the float is not adjustable, verify the hinge pin is seated properly.
 
Well just wanted to post a final update on the milky oil, I have used to boat 3 or 4 times since the 3 consecutive oil changes, and there is absolutely no trace of moisture left in the oil now.
So I guess water found its way in the oil at some point in time, (I would suspect through the gas tank maybe?), and those back to back oil changes with a quick run in between, just drove whatever water / moisture that was left in the fuel system, out.
So thanks for the suggestion pvanv, you were right once again!
 
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