O/B starts on primer and will run. but will not start or re start on choke.

Hi,

I have a Mercury 500 (red band) and just had new carb kits and fuel pump kit installed along with new fuel lines. Motor will not start on choke but if you prime the cylinders, it will start and run ok from the fuel tank. Problem is if you shut down it will not start until it is primed again.

Could the problem be the reed valves?

If so, why does it continue to run after it has been started using priming?

Any suggestions greatly appreciated. Thanks for your time, safe boating this summer.

Regards,
Dave

Re: O/B starts on primer and will run. but will not start or re start on choke.

When you say "prime" you mean spray fuel into carbs? If so, motor may be cranking slowly, not allowing choke to function well, or compression could be low.

Re: O/B starts on primer and will run. but will not start or re start on choke.

Thanks for the response, but priming is done through spark plug holes. once started on the priming engine will stay running through the carbs from the tank and run as it should. If I shut it down it won't restart until primed again through the spark plug holes.

any thoughts or suggestions appreciated.

Rgds.,
Dave

Re: O/B starts on primer and will run. but will not start or re start on choke.

th69judge said:

Thanks for the response, but priming is done through spark plug holes. once started on the priming engine will stay running through the carbs from the tank and run as it should. If I shut it down it won't restart until primed again through the spark plug holes.

any thoughts or suggestions appreciated.

Rgds.,
Dave

Click to expand...

It sounds to me lik the fuel pump isnt getting enough suction or something to that effect. Odd that one with a new fuel pump kit would behave that way though.

Re: O/B starts on primer and will run. but will not start or re start on choke.

Dave, That is not good. Check compression. How fast is motor spinning when cranking?

Re: O/B starts on primer and will run. but will not start or re start on choke.

Hi Chris:
Motor spins fairly fast and compression seems to be good but have not tested with a compression tester. Put the engine in a water barrel today and started it on priming and just let it run for an hour or so and voila it seems to start and restarts just fine now. I am wondering by running it with the mixed gas that maybe the reed valves were stuck and with the vibration of the motor running and oil in the gas lubricating it has all loosened up (fingers crossed).

Next test is to launch the boat maybe tomorrow and take it for a run. All seems great in the water barrel, open water will be the big test.

Thanks to all for the input. I will post on how I make out.

Regards,
Dave

UPDATE: After the motor cool down (couple of hours - back to square one). I am going to check compression tomorrow.