1971 Johnson 50 HP problems

My Dad and I have an old boat with a 1971 Johnson 50 HP. It ran fine the first couple of times, but today we ran into a couple problems. If you guys could give me things to check for I'd appreciate it. This is the first boat we've had so if you could try to make it easy for me to understand I'd appreciate it. So...we got it in the lake and it wouldn't fire up. After running the battery out we took it home to see if we could find anything wrong with it. We hooked the muff to it and it started fine!? We decided to give the lake another try again. After messing around for an hour we were ready to go. My Dad figured we should try the motor one more time to make sure it worked before we went. We tried firing it and it did the same thing it did at the lake. We checked the spark plugs and they were getting a good spark. Checked the fuel and it was getting fuel. Then we ran the motor for about 15 seconds without the plugs in. Put the plugs back in and it started up fine again. Went back to the lake and again couldn't start the motor. So we removed plugs, ran motor, reinstalled plugs...and it started working again. We idled out of the no wake zone and put it into full throttle, but it hardly had any power. When we put it into neutral we could get to rev up fine, but in forward it had no power at all. So we headed back home and we really have no idea what to look for. If anybody has any suggestions or tips on things to check we'd appreciate it. <br /><br />Thanks,<br />Doug

Re: 1971 Johnson 50 HP problems

Doug..... Assuming that (in the lake), after getting the engine running and arriving at your fishing spot, you simply shut the engine off and did not tilt the engine up, more than likely the carburetors are flooding.<br /><br />This would load the crankcase up with fuel, and removing the s/plugs and cranking the engine over would blow the excess fuel out of the cylinders/crankcase.<br /><br />To check the carburetors for flooding problems, remove the carburetor face plate, then pump the fuel primer bulb. If you can make fuel flow out of the carburetor(s) when you do that, they will require cleaning and rebuilding.

Re: 1971 Johnson 50 HP problems

Or use a shortcut that diagnoses two things at once, without having to remove the carb face plates - <br /><br />First, check the bulb operation by unclipping the fuel line from the motor, pumping the bulb and confirming that it stays hard. If it does, then reconnect the line and pump the bulb again. If it then keeps pumping, you have a carburettor flooding problem.<br /><br />If the bulb does not stay hard with the fuel line unclipped, you have a fuel starvation problem within the tank/line/bulb assembly.