[Going2Baja]

Hi all, 1st time poster here. I just bought a 12' Sea Nymph with a 74 Evinrude 6hp model 6402C (might be 6403C - can't remember and it's late, let me know if there is a difference.) The person I bought it from said the carb was set for 8000 MSL (8000 above Sea Level.) He used the boat in Mammoth Lakes Ca. The motor hasn't been run on a regular basis in 3 years, but it did start second pull. How do I set the mixture to Sea Level? And I hear these motors have a problem with one cylinder not running and the user not being able to tell, how can I tell if this is the case? Any other tips or tricks would be greatly appreciated. Thanks all, my wife and I are headed to San Lucas Cove for Easter and a quick reply would be GREAT!!!!!Thanks in advance for any and all replies!!!Tim FarwellCarlsbad, CA

[Xcusme]

Tim,Welcome to Iboats!Your motor should use a 50:1 fuel mix. As for the testing for a dead cylinder, it's simple really. Run motor on boat or in a test tank. Using insulated pliers, remove one of the spark plug wires from the spark plug. If the motor stumbles, that cylinder is firing. Replace the spark plug wire. Do the same test for the other spark plug wire too. A dead cylinder won't cause the motor to stumble or drop RPM's.If the motor has been sitting for 3 years, replace the water pump impeller. Proper cooling of the motor relies on this part. Replacing the impeller is an easy job for the average person with basic tools and a service manual. Manuals can be ordered from the link at the bottom of this page.

[Going2Baja]

Thanks for the quick reply, I was going to use a 40:1 for the oil. I was really wondering about the fuel/air mixture scre and how to set it for sea level. I'm betting that if the motor was set for 8000 that it is running way to lean currently. I guess a manual is the place to start though. Any idea is a 1973 6hp Johnson manual will be the same as a 74' 6hp Rude motor? Thanks, Tim.

[Xcusme]

Tim, Both of those model numbers are for a 1974 6HP 'Rude. Your carb adjustments are as follows, courtesy of Joe Reeves. Depending on which carb you have, pick one of the following.(Carburetor Adjustment - Single S/S Adjustable Needle Valve)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 1/8turns, start to turn the S/S needle valve in. Wait a few seconds for the engine torespond. As you turn the valve in, the rpms will increase. Lower the rpms again towhere 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 1/4turn, you'll find the smoothest slow speed setting.When you have finished the above adjustment, you will have no reason to movethem again unless the carburetor fouls/gums up from sitting, in which case youwould be required to remove, clean, and rebuild the carburetor anyway.--------------------------------------------------(Carburetor Adjustments - Two Adjustable N/Vs)Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slowspeed = seat gently, then open 1-1/2 turns.Setting the high and low needle valves properly:NOTE: For engines that DO NOT have a shift selection, obviously there is noNEUTRAL position. Simply lower the rpms to the lowest setting to obtain the lowspeed needle valve adjustment.(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up tofull throttle. In segments of 1/8 turn, waiting for the engine to respond between turns,start turning in the bottom high speed needle valve. You'll reach a point whereas theengine will either start to die out or spit back (sounds like a mild backfire). At thatpoint, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find thesmoothest setting.(Low Speed) Slow the engine down to where it just stays running. Shift into neutral.Again in segments of 1/8 turns, start to turn the top needle valve in. Wait a fewseconds 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 hitthe point where the engine wants to die out or it will spit back. Again, at that point,back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speedsetting.When you have finished the above adjustments, you will have no reason to movethem again unless the carburetor fouls/gums up from sitting, in which case youwould be required to remove, clean, and rebuild the carburetor anyway.--------------------Joe (30+ Years With OMC)