1982 30hp misfire ??

[laffen007]

I bought a old boat with this engine. Yamaha 30am 1982 mod. The engine look like its still new . Start easy . I have change to a new coil, new sparkplugs, cleaned tank and petrol. This engine have one coil with cabels out to sparkplugs ( dual fire) . It have one carb . I try to hand pump petrol when the engine run at full speed . No different .

The problem is that when engine starts its not run smooth .... Its like the ignition its wrong and engine shaking a little. When i then start to drive the engine do not have full power and its not the good engine sound. But then you can for some seconds hear that the engine runs correct and can also feel more power. Can this be the CDI unit ?

When i speak with workshop they say this engine is to old .......

[99yam40]

Compression , spark, and timing are all easy to test, so do that 1at.

If all is good then I would look to make sure fuel pump is not leaking into crankcase(pin hole or tear)

Then clean carb and adjust

[laffen007]

Compression simular on both cylinders ..10kg . Timing 28 deg when full trottle .Pump is not leaking . Its look like that is cylinder one (upper)that have the problem .This spark plug look dark an little" wet" . It's three things I think it can be ... Cdi unit or leaking seal in bottom on engine or reed valve . The boat should do 20 knot but only do 10 ....