Running w/o airbox...1978 115HP Evinrude

[herefishyfishy]

I've read on the boards that on some motors you shouldn't run with the air silencer removed and other engines it's ok. The airbox has been removed on my motor since I've had it and I was wondering if this is ok for this motor or if I should replace it.

 

[Dhadley]

Re: Running w/o airbox...1978 115HP Evinrude

As far as running quality it wont hurt a thing on your motor.

 

[WillyBWright]

Re: Running w/o airbox...1978 115HP Evinrude

It'd run quieter with it. I doubt you'd notice any decrease in performance.

 

[ledgefinder]

Re: Running w/o airbox...1978 115HP Evinrude

The early V4s had an airbox with the opening only at the top, facing back towards the flywheel. I ran across a 1969 V4 ad saying that the whole motor was sealed so that it could stay running with water nearly up to the flywheel! They meant if wave came up against the back of the boat - not running that way fulltime. Explains the gasket on the old airboxes. Not sure if yours has it, the newer airboxes have openings on the sides.

 

[Chinewalker]

Re: Running w/o airbox...1978 115HP Evinrude

Is it possible that there is some intake tuning built into the carb covers? I know a friend of mine played around with his 15hp Evinrude's intake cover, moving it in and out while the motor was running on a test wheel and found that he lost between 25 and 50 RPM when the cover was anywhere but where it was placed from the factory. His reasoning was that there is a pressure wave created at the carb mouth that can be "bounced" off the cover to cause a bit of a charging effect. He races the 15A OMCs and has played around with just about anything you can think of to make them go...<br />- Scott

 

[Dhadley]

Re: Running w/o airbox...1978 115HP Evinrude

Yes, some of the OMC carbs are in fact designed to pull air from in back of them. The V4, V6 & V8 carbs are some. If you remove the airbox and ram air down the throat it can really mess up the running quality. Even if you rejet to compensate for removing the airbox cover. A lot of motors have the air inlet in the back of the cowl.