Air intake for a 1974 9.9hp Evinrude

[moot40sw]

I recently bought and refurbished this motor. I installed a new water pump, thermostat, and grommet on the water delivery tube at the powerhead. I disassembled the carb, replaced the float and float valve, and cleaned everything. I also synchronized the throttle plate so that it idles nicely. It runs like a champ, as long as the hood is off, as soon as I install the hood, it runs super rich, missing terribly. As far as I can see, there are only two 1/4" holes in the housing to allow air flow to the engine. My question is, should there be more air intake to allow this motor to run? I'm about ready to punch a hole through the housing to let the motor get enough air to run properly.

 

[hardwater fisherman]

You may have an exhaust leak. And if your running in barrel try using a fan to blow away the exhaust.

 

[moot40sw]

You may have an exhaust leak. And if your running in barrel try using a fan to blow away the exhaust.

I was actually on the water, I'm beginning to wonder if someone put a 15hp main jet in the carb

 

[oldboat1]

Are the plug wires out of the way of the latch hook on the back of the cowling?

 

[tphoyt]

I was thinking the same thing.
Make sure all your wiring is in order and no lose wires to short to ground when the cover is on.
You could be losing a cylinder due to a short.

 

[moot40sw]

Are the plug wires out of the way of the latch hook on the back of the cowling?

The bottom cylinder plug wire is double wrapped, and routed through the supports on the thermostat cover, so I don't think it's shorting out.

 

[tphoyt]

Try wiggling the wires around while it running and see if anything changes. Any chance there is some lose Insluation in the cover thats getting sucked into the carb throat?

 

[moot40sw]

Update- I was going to go through the carb again, and found out the fuel line split at the fitting on the carb. Apparently dumping premix in the housing caused the over rich situation. She runs great with the new fuel line installed.

 

[tphoyt]

Great news
Now get out of the water.

 

[Sea Rider]

The powerhead's lower gasket might be already dried, hardened, burnt, lets exhaust fumes inside the cowl and straight into the carb, when the cowl is removed the motor just sucks pure air, re torque tight all lower bolts with a wrench, if continues need to order and change that gasket...

Happy Boating​