Rough idling 1989 J50TLCEC

[ob15]

Let me start off by giving a little history leading to my problem. Out boating one day and the motor started running real rough (kind of surging). I wasn't sure what had happened because the carbs were just cleaned and the motor was running great. I finally figured out that the diaphragm in the OMS had ruptured and fuel was being sucked into the engine block through the pulse limiter. I got all that fixed. Thankfully I installed and new OMS a few years ago so I was able to rebuild it instead of buying a new one. When I rebuilt the OMS I did check the pulse limiter to make sure it still functioned. Does it normally take some pressure to activate the check valve inside the limiter? I couldn't just blow into it to get it to work I used a small amount (low pressure) of compressed air to check it. And it is the blue colored one for the new OMS

Now to my problem. The lower cylinder doesn't seem to be getting enough fuel during idle. Off idle runs great. I also noticed a small amount of fuel squirting out the intermediate orifice when idling. When I bump the primer the motor idles fine. I have cleaned the carbs 2 or 3 times since this happened (cleaned as recommended).

My thoughts are that the reeds were affected when I had the problem with the OMS. Does this sound correct? I'm thinking about taking off the intake tomorrow to investigate but will wait for advice.

Thanks in advance.

Dave

 

[SparkieBoat]

Re: Rough idling 1989 J50TLCEC

I see no reason for the reeds to have been effected. If it were reeds your carb would be throwing out fuel at WOT. possibly your idle passage is clogged. Does your model have the idle adjustment screws? it is a very small passage and can become clogged easily. that is where I would start looking from the symptoms mentioned.

 

[tashasdaddy]

Re: Rough idling 1989 J50TLCEC

#1 you do not have an intermediate orifice, the one on the top center of the carb is the idle orifice, since it is spitting, i would investigate. the screw on the starboard side of the carb is the air mixture. you have to remove the orifices to clean them. see TOP SECRET FILE.

 

[emdsapmgr]

Re: Rough idling 1989 J50TLCEC

Sparky's right on regarding the reeds. Unlikely. When you have a bad reed, you will usually get fuel/compression blowback through the carb throat-that is very visible. These carbs are very sensitive to old, dried up fuel in the passages, esp the idle circuit passages. When you overhauled the carbs, you need to pull all the jets out: idle, mids and high speed. Clean and visually check for debris. Also, need to spray an aerosol carb cleaner through each orfice and then compare the outlet spray volume with the same orfice on the other carb. Since the butterflys are closed at idle, they get their fuel through the idle circuits (passages) only. They must be clear. Checking spray volume is a good way to compare passageway flow.

 

[ob15]

Re: Rough idling 1989 J50TLCEC

Yes I have the idle adjust screw. I've had the carb apart 3 times, soaked, used small wires, sprayed canned carb cleaner & compress air through it all (as recommended). Sorry about the orifice name, that's what the Johnson service manual called it. I thought it was the idle orifice. I'll get another carb kit and clean it our again. Maybe I'll get all new jets as well just to be safe.

What would cause fuel spitting out the idle orifice?

Thanks again.

 

[SparkieBoat]

Re: Rough idling 1989 J50TLCEC

sounds like your jets are ok..clean the idle passages. check your idle screws and make sure that they are not shanked from over tightening. stick a straw from a can of carb cleaner in the hole and spray..see if this helps. Before removing your idle screw..turn it in until it reaches a "soft" set, and count the turns in, when reinstalling the screw, take it back to a soft set then adjust out the appropriate number of times.

 

[ob15]

Re: Rough idling 1989 J50TLCEC

Thanks. I will do that and let you know. Takes a few days to get a rebuild kit here.