Merc 4 hp 1971 model

[Lubosleftboot]

Hi guys

Got this small merc and it has a problem that is perplexing me. The engine will start and run for 5 minutes but then it cuts out and refuses to start at all.

The carb is spotless has fuel in the bowl and the primer bulb is hard so that rules out the fuel pump or a blockage...Also ran the motor with the petrol cap of the fuel can just in case it was a blockage in the fuel tank breather.

Any advice on this problem would be appreciated..and here are a few pics of the motor

Regards LLB

 

[Wingedwheel]

Re: Merc 4 hp 1971 model

How long before you can re-start your motor? right away, or does it need to cool-down.

 

[Lubosleftboot]

Re: Merc 4 hp 1971 model

How long before you can re-start your motor? right away, or does it need to cool-down.

Hi WW

Thanks for the reply mate and the engine will restart straight away...I am also noticing that it will tick over but will not rev...

Could this be to do with the advance retard unit on the points perhaps.?

The plug is black and oily as well as if the engine is running to rich...I have tried all different settings on the airscrew from 1 turn out to 4 turns out at increments of 1/4 of a turn too no avail...

Regards LLB

 

[Wingedwheel]

Re: Merc 4 hp 1971 model

I'm wondering if perhaps you might be flooding. If the float needle and seat aren't sealing properly it could be slowly dumping gas into the carb until it can't take anymore. You can do a rebuild, or use some valve lapping compound to re-seat the needle. Make sure you clean your carb thoroughly to remove any excess.