90 hp Johnson leaking fuel when titled - The Hull Truth

Klamathcoho · 05-26-2009, 12:12 PM

Howdy folks,

A while back I posted about an issue I was having with my 1989 Johnson 90 hp VRO... it would only run with the fast idle up.

Tore apart the carbs, cleaned them, installed new jets and adjusted the floats... runs like a top.

Now I have a different problem. When the motor is fully lifted and the tilt lock is engaged, I get a small but significant amount of fuel leaking from the lower carb (maybe a couple of tablespoons full, from the right side of the main orifice). No leaks at any other position. Float drops were set as per specs from my OMC factory service manual (1", + or - 1/8").

Should I chalk this up as normal for a motor of this vintage? I hate to be dripping fuel onto the motor well (and ultimately, into the water when). Should I try adjusting the floats with a little more drop?

A1 Outboard · 05-27-2009, 06:52 AM

Float drop is not the critical setting on these carbs. The float level is set with the carb inverted and the float is adjusted so top of the float is parallel to the carb body. Check this on all your carbs.

Klamathcoho · 05-27-2009, 11:18 PM

Unfortunately, that made the problem much worse.

With floats adjusted level with the bottom of the carbs (with carbs inverted) I now have fuel leaking from the same vent on both carbs, with engine even slightly tilted.

What gives? I'm looking at the Johnson factory manual for the motor and it calls first checking the float level with a special gauge with the carbs inverted, to ensure they are square, then adjusting the drop so that it is 1" + or - 1/8", or 22 to 28 mm.

Should I just try this again, with the drop set to 28 mm? I'm using brand new needle and float valve. Might the Sierra carb kit have bad a needle/float valve?

A1 Outboard · 05-28-2009, 07:14 AM

Float drop will not make the carbs leak. Float drop insures the valve will open far enough to let fuel into the bowl without sticking on the bottom of the bowl. It is possible your needle and seat assys. are bad. Try some new ones from a Bombardier dealer.