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1974 Evinrude outboard missing air silencer?

J

Jimbrown

New member
Hey guys, I just bought my first boat today with a 1974 Evinrude Triumph 70hp outboard and when I got it back to my house I popped the engine cover off and a bunch a debris was in the motor area such as dead leaves and cotton fluff from cottonwood trees or cattails. I clean it out and notice that the carbs are exposed with nothing covering them.. I do some research and I saw that the outboard should have something called an "air silencer" not sure if it acts as an air filter but I know that if I tried starting the engine it would have inhaled all that junk and ruined the engine so thank God I checked under the hood.. I was looking around to see if it's fine to run the engine without an air silencer and some people purposely do so for more intake etc.. anyways would I cause any engine damage without running a air silencer for any length of time? I heard it causes the engine to run leaner so should I go with a 40:1 mix vs 50:1? Or mess with the carb screws? What do you guys think?
 
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The carburetors do have mixture screws in 74.-----Should be easy to find that assembly.-----Those motors never used an air filter.
 
The air silencer does nothing to performance 50:1 with a TWC-2 grade outboard oil is all thats necessary. Replace the fuel lines and rebuild the fuel pump then you can rebuild the carbs if necessary.
 
Yes, it is supposed to have a silencer (not an air filter). And yes it does affect performance to some degree. It is part of the exhaust tuning system which involves sound waves to be effective. It won't really harm the engine to run without it, but all that needle valve link stuff is involved.

http://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1974&hp=70&model=70443M&manufacturer=Evinrude&section=Intake+Manifold

Run it on 50:1 like the factory said.
 
Now that I think about it, I believe I am mising the whole intake manifold entirely... Here is a picture of my engine and what I am talking about. 33028712_1129707607170404_7034185416051785728_n.jpg
 
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It won't cause it to run lean without the air silencer?, btw thanks everyone for the help.. just a kid trying to get some fish this summer haha.:cool:
 
Sorry but it wont be fine without it!!!! It will run lean and could damage engine. It will be OK to test run in barrel for testing
 
faztbullet said:
Sorry but it wont be fine without it!!!! It will run lean and could damage engine. It will be OK to test run in barrel for testing
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Would running a richer fuel mixture counteract that? The guy I bought it from apparently said he doesn't know too much about motors. Said he had been running for several years in its current state with no issues.. I pulled the spark plugs and all showed signs of oil, not lean or fouled..
 
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They made that 3 cylinder motor for many years.----Many shops would have those on the shelf.-----Make some calls.---Even newer airboxes would fit I would think !
 
Don't confuse "lean" fuel / air ratio with "lean" fuel / oil ratio. Two different things. In your silencer issue, you are concerned with fuel / air ratio. Oil has nothing to do with it (well it does but on a VERY tiny bit---not worth discussing on this matter)
 
fdrgator said:
Don't confuse "lean" fuel / air ratio with "lean" fuel / oil ratio. Two different things. In your silencer issue, you are concerned with fuel / air ratio. Oil has nothing to do with it (well it does but on a VERY tiny bit---not worth discussing on this matter)
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Thanks for educating me :p, I am a squid when it comes to machines but am trying my best to learn more lol
 
If the spark plugs come out a nice toasty brown on the center electrode insulator i wouldnt lose any sleep running it without the baffel. If the plugs burn a powdery white be concerned. Spark plug color is good thing to be aware of when servicing any engine.
 
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