84' 90hp Johnson not getting enough air to run at idle

[donson65]

I'm back with more questions concerning my 84" 90hp (j90mlcrd).
With the boat in the water, idle adjusted ( at this time without rpm guage) motor idling great I place the engine cover back on and the motor runs a little ruff and then dies out. I've made sure all openings for air are unobstructed. I can't see where the cover could be hitting something. It sound as though the engine isn't getting enough air. Would a to low of an idle speed combined with a restricted air flow (cover on) cause this ?

Don

 

[F_R]

Re: 84' 90hp Johnson not getting enough air to run at idle

You have an exhaust leak somewhere, allowing exhaust fumes to enter under the hood. It only take a whiff of exhaust to mess up the running.

 

[kenmyfam]

Re: 84' 90hp Johnson not getting enough air to run at idle

Plug wires may be shorting (sparking) out with the cover on. The cover is properly vented ??? Yes ???
Just a couple of ideas.

 

[emdsapmgr]

Re: 84' 90hp Johnson not getting enough air to run at idle

Your lower cowl should have a vent under the bottom carb. Make sure it is unrestricted. Also, your upper cowl should have a vent in the back under the rear handgrip. Some later models did away with the lower cowl vent, and if used with an older (unvented) upper cowl, you can get the problem you mention.

 

[donson65]

Re: 84' 90hp Johnson not getting enough air to run at idle

Got the boat into the water yesterday to check if the engine was going to die out at idle with the hood on. Well she ran like a champ. there was a breeze so the exhaust fumes weren't hanging around the air intakes. At this point I would agree it was the fumes choking her out.
Thanks again for all your help.

Don