70 horse johnson acting stupid

[dr_jeep]

the engine in question is a 1985ish 70 horse johnson. a little background: had the boat for about two years with no trouble at all until july. installed a new power pack and an ignition switch and it worked perfectly. then about a month ago i was running across the lake and with no warning it nearly shut down. pulled the breather cover off and it would idle but it was spraying gas out of the bottom carb. i rebuilt the bottom carb and it idles better but still sprays gas out when i apply the throttle. i checked the compression and it was good on all three cylinders. put new plugs in and tried it again, no ghange. please helpemoBang

 

[Fuzzy]

I had a 77 70hp johnson. Rebuild all carbs at once, not hard. Take a few pictures, taker her apart and then put her back together. I would also replace the gas lines if they look soft, might be collapsing and starving the engine. Don't want to keep running it lean, score or seize a piston or wall, but it almost sounds like a carb above is having a float sticking and then the fuel bowl fills and all fuel goes down to a bottom carb where it you see it spitting out. I had something similiar and the three carb rebuild cured all.

Fuzz

 

[jon the fisherman]

I too had this problem on my 90 merc, it is the old inline six. It had three carbs, and my middle carb was spitting gas. The float was old, it had a whole in it, and was sunk.

 

[Bubbakat]

While you have those carbs off look in behind them with a good light and see if the reed valves are laying flat and not bowed or twisted. The symptoms you are describing acts just like a reed valve not sealing.

 

[hl&s]

Sounds like compression is pushing gas back through the carb as the rpms increase. Check the reed valves like Bubbakat has already suggested. A restricted exhaust can also force fuel/air back through the carbs as the rpm increases but will usually affect all carbs. Hope you get it fixed.