Help: accidental decarb?

[goldnugget]

Hi guys, was getting the boat ready for a trip to Noosa this coming week, got fresh fuel (the last lot I gave away...seemed to be a 25:1 mix which for a 70hp Johnson is no-no, and sat for donks before I bought it and was fair bit smokey too), new plugs, and while I was at I thought I'd move the throttle controls to somewhere more comfy. Well after a bit of pissfarting around, and checking clearance for full throttle etc....anyway in the end it went back where it started :blush: ...then I thought I'll fire it up again..water going through the muffs...fire it up...not starting..again..again..oh crap I'm thinking..then I clicked that with all the mucking around with the throttle that sure enough its flooded (bigtime)...So after a few attempts it fires..crap load of smoke, and then all this crap starts to come out the exhaust, and where the propellor meets the bottom part of the engine, and sprays the fence with crap :ohmy: ..(crapping was what I was doing when I saw it all). It was sort of like a thick black oily/greasy consistency. So I shut down, clean it up, fire it up...still doing it but not as much...same again and same result..,the motor seems to be running better, and less smokey. I thought the worst and checked the gearbox oil (fine), and when I ran my finger around the inside of the prop it was thinck and gunky. I'll be firing it up more tomorrow and cleaning it up but I sure as hell wasnt expecting so much crap to run through. The motor was rebuilt through previous owner due to failed VRO, now no vro and the fuel is premixed..I'm guessing the previous owner ran the richer mix after the rebuild and didnt adjust the fuel mix later on.

[CrayfishMates]

Sounds like you had a mission of it mate. Hope it all works out. When I had the last service done, I found the carbies \"gummed\" up with the 2 stroke oil. I hit the carbies with a big dose of CRC Carbie Cleaner and ran it for a bit then hit it again to let it soak. Sure enough on the next trip, gave the engine a good 20minute flat out run and now she is clear and clean, running smooth.

[goldnugget]

I checked the plugs afterwards and they were actually pretty good compared to the last lot which oiled up after 10 minutes idle, thats when I clicked on the fuel.....So I know its nothing major, it took me more by surprise than anything...to top it off my son was watching and when he saw all the crap he went runnig to the missus and yelled 'dads f$%^ked the motor up in the boat!' .

I've calmed down a bit now when I think about what it was, but it didnt look pretty at the time.

[CrayfishMates]

lol at the young fella dobbin you in mate that cracked me up.

[goldnugget]

Yeah..he's only ten..but we let him off on that one....I had more foul words coming out of my mouth.

[rumrunner]

it sounds like it just had a gut full of very rich mixture and could not burn it.

has the motor done its full runn in procedure?

if still running in you must run a 25:1 mixture to allow pistons and rings to bed without excess friction.

normal runn in procedure is about 8 to 10 hrs normall running conditions without excess full throttle opperation!

also fuel does go bad/stale after time and can give the appearence or a extreemly rich fuel mix ratio.

so if it has just been rebuilt that would explain the resedue in the propellor exaust port and it would also explain the excess smoke when running!

hope this helps

Ian

[goldnugget]

Thanks for the reply rumrunner. The boat fuel was what was in the tank when I bought it, and was used for a couple of hours by me, prior to that he had run in the boat (was his fathers), and he had also used it on the river for a few months before it sat in his back yard for at least 6 months. The fuel was bad, I did a test burn out the backyard and it burned for ages...almost like diesel. Even the mower coughed and spluttered a bit. I only just got the new fuel mixed yesterday, but with all the mucking around with the thottle lever I flooded it hugely. I'm going out now to give it a quick idle and see how its going. I just want to make sure it runs out the last of the crap before the trip away on Wednesday.

edit (added): Ran the motor for about 10-15 minutes and seems okay, no new gunk, just a bit of leftovers at the prop. What little smoke there is also seems to be thinning out, plugs are okay, but just a little oil around the rim. I'm guessing this will clear itself after a good run in a couple of days.

[billythakid]

2 stroke will seperate if left for awhile . had the same thing

happen on my dirtbike when i busted my leg and forgot to drain the tank

oil / fuel will seperate over time .

sounds like it picked up alot of the oil and blew it through onto the fence:S