Starter motor doesn´t kick in

[baksmällan]

Helllo,
When trying to start I only get a buzz sound from the engine. The starter motor doesn´t kick in. I have power in the battery. I even borrowed a battery booster, but the starter motor didn´t react any differently. I have tried to short circuit the starter relay without any different result. After waiting a few hours I tried again with the same result, but on the third attempt the motor started and ran nicely!
Now I don´t know how to repair an engine that works !

It is a Yamaha 60 hp Autolube from 1989: 6H2 S 100508

Thanks for your advice !

[baksmällan]

IMG_20240801_123214r.jpgUpdate
The following day the starter is faulty again. There is only this buzzing consisting of a clicking sounds in quick series.

Today time I had brought jumper cabels and I connected directly from the battery to the red connection on the starter motor. This got the start starter motor going and the engine started ! :-)
I tried short circuitng over the relay again, this still only gives buzzing sounds.

[99yam40]

my guess is a bad connection on either the positive or negative cables,
or a bad cable itself

[baksmällan]

I have found the problem. When I put the jump cable from the battery on the input to the relay then everything work normally.
So I have have a bad power cable that needs to be replaced. :-)

What cable cross section do I need? The cable will be 2.5m long.

[99yam40]

I would check the connections of that cable before saying the cable itself is bad.
but you can always look at what you have to see what gauge it is