Mercury 500 advice needed please

[purplemk]

Hello
I have a Merc 500 1972 4cyl 2 stroke, I bought it recently and saw it running and it seemed ok started after about 4 pulls no problem.
Now I come to use it I cant get it to start much to my dissappointment!, I've tried all manor of starting positions with choke without/ with throttle open etc etc.
Throttle closed choke off after 4ish pulls it fire's for a couple of seconds then seems to run out of fuel, frantic pumping of the bulb will just keep it running for a few more seconds, pump the bulb again and retry same every time. If I touch the throttle it dies/pull the choke same thing.
I have stripped the carbs and cleaned them/blown out the jest with airline, checked the fuel pump diaphragm and valves all ok, new fuel line and bulb fitted, new petrol and clean tank, air bled from the system on the carbs etc.
I'm at my wits end with it:facepalm: and summer will be finished by the time I get it going at this rate(
I has good compression and as I have seen it run recently all be it brefly I believe it to be a healthy engine, Its just not getting enough fuel it would seem.
Does any one have any Ideas?? or know the correct setting for the ajusters on the carbs???
Any advice much appreciated
Thanks

 

[merc850]

Re: Mercury 500 advice needed please

Have you done a compression test?
The lo speed needles should be 1 1/4 turns out from seated to start, then adjusted to run properly under load. Tilt the motor all the way up and squeeze primer bulb until fuel flows out of carbs, this will show if you have fuel flow.
Check to see if you have this carb and clean the filter screen.

 

[purplemk]

Re: Mercury 500 advice needed please

Hi
Many thanks for the info, I only just saw your reply as I did not get any notification that I'd had a reply to my question.
As it happens I was fighting with The engine again today, until my arm got tired of pulling it over
I fitted a new fuel pump kit as the old diafragm was looking past its best but still no joy with starting. I'm not sure if there is a filter in that T conector but I will certainly check!, as it would seem to fit with fuel shortage.
Do you normaly start these engins with or without throttle?
Thanks

 

[purplemk]

Re: Mercury 500 advice needed please

Have you done a compression test?
The lo speed needles should be 1 1/4 turns out from seated to start, then adjusted to run properly under load. Tilt the motor all the way up and squeeze primer bulb until fuel flows out of carbs, this will show if you have fuel flow.
Check to see if you have this carb and clean the filter screen.

View attachment 93473

No I have not done a compression test but it feels consistent and ok when pulled over and as I have seen and heard it running not that long ago I am quite confident its ok in that department.

 

[rowdyboy321]

Re: Mercury 500 advice needed please

put gas in squirt bottle and give it a shot and see what happens.

 

[Mi duckdown]

Re: Mercury 500 advice needed please

You can never be sure, until you do the compression test.
That's Test NUMBER 1.
Before you waste any more time and money.

 

[purplemk]

Re: Mercury 500 advice needed please

You can never be sure, until you do the compression test.
That's Test NUMBER 1.
Before you waste any more time and money.

Hi
Ideally yes, but as its manual start I can tell there is nothing too far out as far as compression is concerned. I'm quite sure its something simple that I just have not found yet because it does fire just won't run.