Re: 1983 70hp Johnson carb upgrade
Bought the motor used.. Started motor before buying and also checked compression. Motor needed a tune up for sure and owner stated he had taken it to the lake but could rarely get it to come up on plane because it would stall out and die when you tried to take off. He had other boat so this one set around for a few years before he decided to sell.
1-Compression is 120's all 3 cylinders.
2-Overall looks pretty clean and unmolested.
3-things i did..rebuilt carbs (set floats etc, etc as per manual), rebuilt fuel pump, new plugs gaped properly, all new fuel lines and inline filter. Ran good on muffs. Took it to the lake, falls on its face and dies as soon as you try and take off. Fuel bulb pumped up tight, air valve open on tank, filter full of fuel.
4-took it to boat mechanic for link n sync. He tweaked and checked it including a new rectifier. He said spark looks great. coils and power pack look newer. Ran great on muffs and in tank. Take it to the lake and it falls on its face as before. In most cases just dies and cannot get it up on plane at all. Mechanic even stated he wished it had adjustable carbs the first time I took it to him.
So.... Been reading a lot about others having same problem and in many cases it seems related to the nonadjustable carbs...
My next lake test will be choking it upon trying to take off and or giving it a light squirt of premix into carbs upon takeoff to see if I can verify its a fuel issue rather than throwing stator, pickup coil etc at it which = $$$..
Also going to recheck timing...
Found a cheap set of adjustable carbs, serial #'s show they are from 1986 60 or 75 hp motors.. ??? Seems another guy went that route and it fixed what he called the two year struggle to get his 70hp running correctly.
Any thoughts appreciated...
