I recently acquired a 1978 Johnson 70 hp outboard with a boat I purchased, the model number is 70EL78C. It originally would try to start then die for the previous owner. When I got it home I cleaned gas tank and fuel pickup emptied float bowls and put new gas mixed 50:1 and it started right away and idled fine on the muffs. Just to satisfy myself I tested compression and it read 120,119,119 on all three cylinders needless to say I was very relieved! Well I loaded the boys in the truck and took it down to the river to run it around. At first it was hard to start, then I couldn't get it above idle speed without the engine bogging and dying on me, I could push the electric choke when it was dying and it would come back to life...so time for a good carb clean. To make a long story short I soaked carbs and cleaned everything thoroughly, adjusted linkage and it fired right up and I was able to accelerate the throttle on the muffs...so back to the river I go. This time not much problems getting it started, idled fine and went into gear fine however it now will only go about a quarter speed even with throttle pushed to fast. If I push the throttle to fast it bogs and dies, I can still play with the key choke to get it back to life but it is waaaay underpowered, we are talking like 9 mph at full throttle and this is a 70 hp engine on a 14' boat! So basically it's not running full out and bogging down. I pumped the tank bulb while running and it did nothing...
I am stumped as to what to do now, how should I proceed to diagnose and resolve issue?
much thanks,
Bill
I am stumped as to what to do now, how should I proceed to diagnose and resolve issue?
much thanks,
Bill