How to test

[zerop3]

While looking at the wiring diagrams for my 63 40hp evinrude i noticed that the lower cylinder points and coil are connected to a cut out switch and safety switch. I have not had the time to test and see if one of the cylinders a re dropping off when the motor is off idle. But I was wondering how would you test these two items to see if they are functioning correctly or if they are engaging at the wrong time?

 

[rwise]

Re: How to test

Is it running poorly? sounds like an over rpm (runaway) or maybe over temp circut. Edit your post and add the modle number to it some will want it to look up info for you.

 

[zerop3]

Re: How to test

No it runs smoothly at idle and smooth acceleration. It just doesnt seem to have as much power as I would think that it should. I do know that there is an issue with the air intake that I havent been able to check out yet. It runs better if I have the cover off or the door to the carburetor open. Someone has mentioned that I might have an exhaust leak. My question is how can i check to see if my motor is creating to much vacuum when accelerating and cutting off the lower cylinder, because it will plane out if the cover is off it jsut takes a long time. The motor is a 40hp evinrude model #40352D and serial #E02386. It is on a 1963 14ft larson runabout. The only things that I have done to it so far are new spark plugs, rebuilt carburetor (has fixed high speed jet), new fuel filter, all new fuel hoses from tanl to fuel pump to carburetor, I dont belive I cahnged the fuel pump though. I dont have much time to actually work on the motor that is why I am asking for several different ideas on what to look for so that I will have a lot of ideas when I do get the chance to check it out. Thanks in advance for all of the help.

 

[rwise]

Re: How to test

Have you tried running it with the hood/cowl off? If it has an exaust leak that should let it run good. Maybe someone that has the same engine will pick up and give you more ideas. But it could be sufficating its self! Try it with the hood removed and see what it runs like. The vacum switches could be disconnected for a test but, it could be harmful to the engine if it over revs! Rods are not supposed to stick through the block, LOL. If you disconnect it be carefull, keep the kill switch in the circut, etc...

 

[Paul Moir]

Re: How to test

Since you've got brand new plugs in it, tell us what they look like at their firing end.<br />If your dropping a cylinder, the most common reason is a cracked ignition coil. Unfortunetly, the only conclusive way to test for that is to remove them and visually examine them. However, sometimes you can tell by how far a gap you can jump with them. You should expect to see it jump about a 3/8" gap.<br />What happens is, as the rpms pick up the magneto's voltage picks up, and at the same time the spark plug's gap gets harder to fire across because it's firing closer to TDC. So the spark finds an alternative path through the coil's insulation to ground.<br />You can isolate the ignition system from it's various cutouts by disconnecting and isolating the two wires from the armature plate up underneath the flywheel. You'll have to choke the engine to stop it though.<br /><br />Good luck!