Evinrude 3 HP Lightwin 3302

I have a Evinrude Lightwin model 3302 year 1963. I've been tuning up the carburetor. When I took off the silencer, the flame arester screen fell off. A friend tol me not to put it back on because it restricts the airflow to the carburator. It does look like it would cause a 50% reduction. He said that was the difference between a 3 HP and 4 HP Litetwin. Is this true or what should I believe?<br /><br />Tom Travis

Re: Evinrude 3 HP Lightwin 3302

Is he saying taking off the screen gives a 1 hp increase? Removing the screen won't do that.

Re: Evinrude 3 HP Lightwin 3302

In fact, it'll run much worse. The carburetor depends on the restriction of the screen to provide the vaccum it needs. <br /><br />The difference between the 3 and 4hp lightwins are:<br /><br />1) The intake on the 3hp is completely different from the 4hp. There are two reeds per cylinder on the 4hp and the intake manifold is shaped differently.<br /><br />2) The 4hp has an exhaust tuner where the 3hp has none.<br /><br />3) The 4hp cylinder head is different. I don't know if this adds power or just angles the plugs.<br /><br />4) Top bearing arrangement different. It has a seal and needle bearing rather than a babbit and oil seal. Presumably this helps with the 50:1 mix ratio.<br /><br />5) - 500 more RPMS<br /><br />6) Piston is different (rings are narrower)<br /><br />I suspect the port timing is different to make use of all those changes. Note that you cannot change a 3hp to a 4hp since the intake crank half is married to the bore crank half.

Re: Evinrude 3 HP Lightwin 3302

Ditto what Paul wrote:<br /><br />If it is plugged, clean it. Otherwise you would want to reinstall it.

Re: Evinrude 3 HP Lightwin 3302

My buddy is standing over me with his hands crossed, shaking his head. I guess I'll take some tools to the local lake and try it out both ways and report on what I find out.<br /><br />Thanks for all the info.<br /><br />Tom Travis

Re: Evinrude 3 HP Lightwin 3302

Tom,<br /><br />Put it in there. It won't run right without it. Been there done that. Those engineers were NOT idiots. <br /><br />Oh you can get it to run, without it, but your adjustments will be way out of whack.<br /><br />Besides, I defy anyone to tell the difference between 3 and 4 hp on those old OMC's anyway. They were both slow, but they ALWAYS got you there and back.