Low Rev, Black smoke and Stall out

[Jim L]

My 2GM20F when I push throttle past 2600 rpm would produce loads of Black smoke in the water behind me and eventually choke out drop rpm down to 1500. I would throttle back let it rest then push it back up to max of 2400. Last night coming back in it gradually got slower and slower to the point it slowed in rpm and eventually died. Had to get towed back in last night fortunately just at last marker into the Marina. Have been chasing this for awhile but it has finally hit the limit. It has gotten worse as time went by. I noticed last night that with my last oil change in April some 20 hours ago that the crank case was way over filled. Notes; Air Filter Clean, Prop the Original, Fuel Filters just cleaned and replaced in June. Did notice that my Secondary filter bleed screw is letting some fuel out. When I tightened it it just turns.

Any Thoughts Have been reading other posts but can not find like issues.

https://www.dropbox.com/s/9r74fsxvutow4qb/IMG_3440.MOV

 

[Charles Erwin]

Highly probable the lift pump - fastened on the right side of the motor just above the oil dip stick - is leaking and diesel is falling into the crankcase. Thus the oil level rises.

Provide new pump/sealing washers on the tube. Also change your oil and oil filter.

This ought to be < $100. Unlikely you can find kit to fix present pump but if so then OK if you feel up to lift pump disassemble/reassemble.

Charles

 

[Jim L]

Would this account for the oil turning black right after an oil change. Could pump also be picking up some oil into the fuel supply?

 

[Ralph Johnstone]

Overfilled Crankcase ..........................

the crank case was way over filled. https://www.dropbox.com/s/9r74fsxvutow4qb/IMG_3440.MOV

........................ certainly sounds like fuel (or water) leaking into the crankcase but not neccessarliy the cause of the engine slowing and stalling.

With all that you've checked, we'll assume that the shaft is turning easily by hand.

Next thing to check in order of the easiest first, would be the mixing elbow.

 

[Jim L]

Actually need to give that a try.

 

[Benny17441]

If you have a lift pump leaking fuel into the crankcase it would surely explain the high oil level but it would not account for the loss of power and stalling. In many instances the condition you describe can be the result of a plugged mixing elbow.

 

[Ken13559]

Could be the mixing elbow fouling up.

 

[Jim L]

Could be the mixing elbow fouling up.

Lets hope so. The votes are listing toward the mixing elbow. Supposedly was changed just prior to my purchase. Maybe the fact I have been running at lower rpm.

 

[Ralph Johnstone]

You can Drink ................................

Maybe the fact I have been running at lower rpm.

........................ smoke, chase easy women, and eat gallons of Haagen Dazs chocolate ice cream but running your engine at low RPM's is the WORST thing you can possibly do to your health .

 

[Jim L]

Thanks for the Help Guys. Not sure if my little video link was of any help or not but tells the story pretty clearly.

Thanks.

 

[Nom De Guerre]

I had a very similar symptom this past weekend. Was out for a motor and the RPM kept dropping from 2600 to 2200. Would idle the speed control and then take it back up to 2400 only to have it gradually drop back down a couple of hundred RPM every minute or so. Found that I could only maintain a consistent RPM at about 1200.

I also noticed, when I jumped down below to see what I could see, that the priming bulb I have before the secondary filter was sucked flat with a vacuum.

Back to my slip, primary filter looks okay, tear into the fuel tank. Pull the pickup tube/gauge mounting plate and see a bunch of loose gunk/junk in the bottom corner of the tank. Look at the end of the pickup tube and what do I find? The screen in the end of the tube is so plugged up that only 2 of the approximately 25 holes in the screen are passing fuel!

Pumped the fuel out, wiped the gunk out of the tank, ripped the screen out of the tube, filtered the fuel back in, and reassembled. She's running a-okay again, easily able to maintain 2500 in gear without vacuuming the bulb or dropping RPM at all.

I'll run it like that for a day or two, and then change out the tank to primary fuel line and the primary filter. That should do it for me, maybe you've a similar issue.

 

[Jim L]

Thanks for the direction. That sounds like good advice to look into in any event. I have not examined inside the tank and should. Just need to jump in full depth.

 

[Jim L]

Replaced Exhaust Elbow running like a champ now.