1974 40hp

[Aussie76]

Hi everyone,
I have a 1974 40HP Evinrude/Norseman outboard motor, Model # 40404s and the Serial # A 107628 and the problem with it is that with the two spark plugs in I can't crank the engine over (when I pull the cord slowly it just stops), but with the plugs out I can pull the cord and it goes freely. The motor hasn't run for over a year now, but when it did run last it went ok.
Is this a compression problem? The spark plug type that should be used are champion UL4J, but the ones with the motor now are NGK B7HS, are these the same as the champions?
Would really appreciate any advise from anyone, thanks.

 

[tashasdaddy]

Re: 1974 40hp

ngk are not the same as Champions, your piston may be hitting the spark plug.

 

[mthieme]

Re: 1974 40hp

I checked a cross reference, they are the same.
So, one less worry.

 

[pequod]

Re: 1974 40hp

Have you measured the reach(thread)on both sets of plugs?

 

[tashasdaddy]

Re: 1974 40hp

your motor was designed for Champion plugs.

 

[tx1961whaler]

Re: 1974 40hp

Go back to the Champions. Some NGK plugs actually screw in further than the Champions, even though the cross reference shows them as compatible.

 

[Aussie76]

Re: 1974 40hp

Thanks for the replies, I have tried the champion plugs and there is no difference between the champion plugs and the NKG plugs. There is high compression with either of the plugs and even when I block the holes up the compression is high. When the plugs are not in and the holes are free there is no compression. Is there a decompression valve on this model? Is there anywhere on the web that I can get a copy of the manual