ROUGH RUNNING 25 JOHNSON

[carlynew]

I need help/advice for a recently acquired 1988 25 Johnson that has a bad cough. Essentially the motor coughs when started and maintains that cough to the point where no power can be developed. I've had the local mechanic looking at it and he did a few things with the carb/Fuel system (Cleaned, new Seals/gaskets, checked for cracks in body etc.) to no avail. Motor has strong compression (125 psi) in both cylinders, Fire is great on both coils, Reed block is intact so I'm lost as to what could possibly be causing this problem. All advice is appreciated.<br /><br />--------------------------------------------------------------------------------

 

[OBJ]

Re: ROUGH RUNNING 25 JOHNSON

Welcome to the forums hard8.<br /><br />Does the cough persist if you give it the "gas"? Does the engine have an auto (solenoid) or manual choke?<br /><br />Do you know if the wrench disassemble the carb blew out the passages with compressed air?<br /><br />The problem you are having sounds like the engine is way to lean at idle which would mean you need to richen the mix with the low speed needle adjustment. <br />Do you also know if the wrench set the cam follower and cam? Look in back of the carb and you will see a roller that lays against the cam under the flywheel. The cam pushes on the roller at the right time to open the throttle. Look for a hash mark on the cam. When this hash mark is centered on the roller, the throttle plate should just start to open. If this setting is way off, it will cause the problems you are having.<br /><br />Keep us posted.....thanks.

 

[carlynew]

Re: ROUGH RUNNING 25 JOHNSON

Thanks for the warm welcome OBJ. The mechanic weht through the Carb and also tried another 25 carb on the motor and got the same result. Needless to say he is puzzled by this and is at a loss as what to do to rectify. Any advice?<br />Thanks.

 

[OBJ]

Re: ROUGH RUNNING 25 JOHNSON

Hard to put a finger on it without putting the eye on it first hard8. But we generally come up with some ideas here on the forums.....lottsa good wrenches here.<br /><br />Well....it's starts to cough and keeps on till it stalls....I still would like to know if cracking the throttle prevents this. If it does, we could be looking at a good air leak, either on the block or in the fuel lines.<br /><br />Were the tank vent, fuel line to the engine checked out?<br /><br />On the other hand, even though the spark is good on the spark tester, you could have a bad charge coil under the flywheel or a power pack heading south after the engine warms up.<br /><br />Did the wrench check the fuel lines to be tight and not obstructed? Was the fuel pump checked? If the diaphram is busted, you may not be getting the gas needed to run. Here's something for you to try. The fuel pump is the triangular shaped box on the side of the engine with the fuel lines coming and going from it. Remove the two screws securing it to the block and pull it away a little. Now pump the primer bulb and see if any fuel shoots out the back of the pump. If it does, the pump is shot.<br /><br />Take a look at the above and see what ya' see. Again, without being there, all we can do is suggest what to look at. Hope you find the problem from the above.<br /><br />Keep us posted.....thanks.

 

[G DANE]

Re: ROUGH RUNNING 25 JOHNSON

I had one coughing reel bad, it appeared to be a couple of loose bolts on the manifold to block surface. Retightened, and everything was fine. Look around for air leaks on motor. Oily and messy somewhere ? The intake manifold mentioned wasnt messy though.