Johnson evinrude 18 hp

[flaxterra]

i just got a 1970 18hp motor.

i just got a 1970 18hp motor. runs good other then i idles bad and seems to bogg on top end. the owner told me the fuel pump was the problem. i put in the new fuel pump and it seemd to do better other then it began to spit back. not all the time just sometimes. i pulled a plug wire while running and it cut out. the next time both plugs seemed to have good spark. ran it a while longer and it started to spit back again. not sure where to go from here??

 

[joereeves]

"With the spark plugs removed,

"With the spark plugs removed, the spark should jump a 1/4" gap with a strong blue lightning like flame.... a real SNAP! Doe it?

Compression should approach 100 psi and be even on both cylinders. What reading do you get?

The carburetor should be cleaned and rebuild using a complete carburetor kit to make sure that it is in perfect operating condition.

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note 1: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

Note 2: If the engine should be a three (3) cylinder engine with three (3) carburetors, start the adjustment sequence with the center carburetor.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

When time permits, visit my eBay store at: http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store"