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Classic 50 wonbt starts

jknoah

Member
"Hello, I need someone's h

"Hello, I need someone's help or may be Mr lamb or Noel can help.The issue is starting problem . My 4 cylinder classic 50 won't start by itself but only it starts with spit of mixed gas. However, once it starts it idles and runs fine. So I cleaned carbs and all fuel lines then tried again but it doesn't work.I checked the carbs ,there were enough gas in the bowls but the plugs were almost dry, looks fuel delivery problem. Why does the fuel not get into the cylinders? Yes,The choke valve works fine, All cylinder's compressions are ok and the sparks are good.I cleaned carbs again and tried to start but still no luck. Did I miss anything to check up? It is a 78' Mercury 4 cylinder 50 HP distributor less outboard. thanks"
 
"OK, here's a total long s

"OK, here's a total long shot suggestion from someone with abosolutely ZERO competence to say anything about 50hp Classics.
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Have you checked the idle speed adjustment (if indeed there is one)? My 15hp has the nasty habit of gradually loosening its idle RPM adjustment nut, so after about every six months of running ok, the idle revs start to drop ever so slightly, until one day suddenly it no longer starts except when you manually hold the carb butterfly slightly open. Once you know the game, you just readjust the idle speed setting to spec, tighten the nut as best you can and off you go.

Just a thought..."
 
"Hi noah,The fuel pump sounds

"Hi noah,The fuel pump sounds like it could do with a rebuild,may be a diaphragm on it's way out,or sticking reeds.Have you done a pressure check on the fuel pump."
 
"Low speed idle adjustment,It

"Low speed idle adjustment,It could be the solution I didn't think about that. I'll test the motor tomorrow and let you know result. thanks for your advice ,Tom and Brian."
 
"Hello, Noel I already checked

"Hello, Noel I already checked fuel pumps(there are two carbs and each carb has its own diaphragm )but I couldn't see any damages.And You say fuel pressure and sticky reeds? Could you explain how to check them?"
 
"Noah to check the fuel pressu

"Noah to check the fuel pressure,disconnect the line from the carb,squeeze bulb to to see if there is a good flow,then have someone crank motor,there should be a good flow of fuel out of the pipe.Repeat on other carb.You can also use a pressure gauge,about 4-5psi.Always a good idea to have the plug leads grounded when doing this
The reeds are another kettle of fish. They are behind the carbs,if you have the carbs off you will be to see them,if they are not opening or closing fully it affects the fuel delivery.Sometimes after lying up the reeds get gummed up.If you have the carbs off,GENTLY press against the petal,(the thin metal plates you will see)with a pencil to see if it springs back in.Turn the crankshaft by hand until you count ten either side. I was thinking afterwards that if it is running ok after you do get it started it is unlikely to be the reeds.
Daft question,do you advance the throttle when you are starting?"
 
I tried but the low speed idle

I tried but the low speed idle screw didn't improve the starting problem so I'm going to try Noel's solution tomorrow.
 
"Noel ,You say "there shou

"Noel ,You say "there should be a good flow of fuel out of the pipe" Well,what do you mean that PIPE?
This motor doesn't have a separate fuel pump like a more older Mercury(I see 73' or more older one has a separate fuel pump which connected between bulb and carbs with hose).
My 78' 50 Horse have two separate carbs, those carbs being supplied fuel through "T" hose from the bulb and each carb has its own diaphragm(fuel pump)in one complete unit. Should I remove the carburator bowl to see the fuel flow?"
 
"<[img]"http://www.marineengin

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Sorry on different wave length noah.
Disconnect the line at the T and pump bulb,if flow good then rebuild those integral fuel pumps.
Follow JB's advise for the cyl drop test before you go to the trouble of removing the carbs again.Then it is JB's suggestion of a crankshaft seal gone."
 
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