Motor coughing and kicking back

[ryanc]

1973 merc 200 20hp thunderbuilt ignition.<br /><br />Carb was just rebuilt prior to breaking engine down for new bearings.<br /><br />Problem, Engine starts about third pull and runs what seems long enough to eat gas then it starves and motor kicks back and even once backfired. Gas bulb never gets tight ? Engine can be reved up with no problem. At idle it only runs if the choke is pulled out at least a quarter of the way. It runs only about a 1 1/2 minutes and then kicks off with a cough. thanks for any tips<br /><br />I checked clymer manual but I can't seem to find much on the carb. It simply says on side of carb- "mercarb". The cowling says "thunderbolt" but cylmer mentions "Phase maker" and thunderbolt is only mentioned in the year 1981- up, what happened to 1973?? sure is confusing, anyway would appreciate your help, thanks

 

[IBrokeMyFreakinNeck]

Re: Motor coughing and kicking back

Maybe your fuel pump needs to be rebuilt.

 

[ryanc]

Re: Motor coughing and kicking back

Thanks but we don't have a fuel pump on this motor that I know of.

 

[ryanc]

Re: Motor coughing and kicking back

i have a integral fuel pump carburator which was supposedly rebuilt before I changed out bearings. Had no trouble before with fuel, perhaps my timing is off?? I just don't know where to begin?

 

[Yepblaze]

Re: Motor coughing and kicking back

Any little leak in the line from the tank to your motor can introduce air causing the motor to run out of gas. <br /><br />Just because the bulb never actually gets firm, doesn't mean it's not working. But I seem to have to replace fuel line assy.'s almost yearly for one reason or another.<br /><br />A poorly fitting fuel connector can sometimes cause problems.<br /><br />Maybe the carb/pump needs more attention, or just an adjustment.<br /><br />Maybe you can borrow a buddies tank and try that.

 

[emckelvy]

Re: Motor coughing and kicking back

Try turning the idle mixture screw on the carb in a CCW (rich) direction and see if it quits coughing.<br /><br />Sounds like you may be just a touch lean. Do your adjustments in about 1/8 turn increments, then let the idle stablize for a bit. Note that the best idle mixture adjustment is made with the motor in the water, warmed up and in forward gear.<br /><br />If that's not it, try pumping the fuel bulb when the motor starts to fade. This may tell you a little more about the problem.<br /><br />You may have to pull the integral fuel pump apart to make sure all the gaskets and diaprhagms are correctly installed. If anything's out of place it won't pump fuel properly.<br /><br />Make sure the vent on your fuel tank is open, too.<br /><br />HTH........ed

 

[rickdb1boat]

Re: Motor coughing and kicking back

Even though the carb was just rebuilt, it Still sounds like a problem in the carb. Sticking float needle open, float setting off or clogged jet???. When it dies, pull the plugs and see if they are wet or dry. Also, have a spray bottle of pre-mix handy and when it starts to die, shoot some into the carb throat and see if it picks back up. If it does run back up with a shot of fuel, I'd pull the carb back down.

 

[ryanc]

Re: Motor coughing and kicking back

thanks RB, but what does " I would pull the carb back down " mean?? You mean rebuild it again?? thank you for your reply.

 

[rickdb1boat]

Re: Motor coughing and kicking back

Perhaps, not rebuild it since that was done recently, but at least pull it apart and clean it and check the float adjustment, needle and needle seat.

 

[ryanc]

Re: Motor coughing and kicking back

thanks rick, well I sprayed some mix in it while it was dying and it went ahead and died, making no difference. I pulled the plugs and they were wet.<br /><br />I also found a leak next to gas tank fitting and repaired that but it still made no difference, thanks for your replies.

 

[rickdb1boat]

Re: Motor coughing and kicking back

Could be it's flooding itself out. If the float needle never completly seats, it will continue to dump excess fuel into the cylinders and flood the engine to the point of stopping. What I'm saying, is that it is getting too much fuel and the cause could be a stuck open float needle or misadjusted float. If it were me, and I had good spark, I'd take the carb apart and have a look and clean it out again and check the settings. Best I can offer at this point. Good Compression, Good Spark, Good fuel delivery = Good running motor

 

[ryanc]

Re: Motor coughing and kicking back

thanks again rick, well I haven't gotten around to a compression check,just put new rings, bearings and seals in. I will take the carb tomorrow to the cleaners, perhaps some particles of dirt got into it while we were working on other things, thanks again.

 

[ryanc]

Re: Motor coughing and kicking back

Just an update, took carb apart found dirty screen and a spect of dirt in idle screw jet, float was within specs. after putting together had a leak where diaphram of carb is located, tried to tighten screws but still leaks only when pressured by the bulb. also realized that the gasket between head and carb was upside down and a small hole was blocked by the gasket.<br /><br />tested compression, 60/60 for both cylinders but I found recirc hoses on side of head were spewing forth gas when engine coughed or back fired.<br /><br />during disassembly if ya remember I took all the flywheel apart and the magnets were not in correct position. Finally got flywheel back into right position and she starts up first pull and idles fine with idle screw turned out 1 turn form seat.<br /><br />so, the problem with idle and starting looks to be fixed at this point, but now dealing with low compression reading.<br /><br /> thanks for all your tips, help and time and efforts, robert/ryan