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Outboard wont start / run at idle.

S

Suffire

New member
Hey!

so i've been having alot of trouble with my old merc, its an old 50hp 4cylinder 2 stoke. from 1985 i belive, its with the thunderbolt ignition.
if i give it some throttle when starting it, it starts and runs somewhat "fine".
But as soon as i let of the gas and put it back into idle, it dies instantly. same thing if i try starting it at idle, maybe it fires 2-3 times with the choke on but then dies after that.

i just rebuilt both carbs, and replaced the fuel lines (and filter) all the way from the tank to the carbs. It also has new plugs.
Adjusting the idle mixture seems to do absolutely nothing. if i remember correctly the engine ran fine last season, but there was this one time when i was going at WOT and then the engine suddenly stopped, after this the engine has been acting up.

any tips?
sorry for my grammar, norwegian over here.
 
Did you put new fuel pump diaphragms in the carbs?
Screws for mixture should be set at 1.5 turns out. If it will only run on the choke. You may have to remove the carbs and clean them again.
The idle circuit sounds clogged. How about the floats. Are they set correctly? Float drop and float height?. Do you have good blue spark? How is the compression of the engine?
 
mechanicman said:
Did you put new fuel pump diaphragms in the carbs?
Screws for mixture should be set at 1.5 turns out. If it will only run on the choke. You may have to remove the carbs and clean them again.
The idle circuit sounds clogged. How about the floats. Are they set correctly? Float drop and float height?. Do you have good blue spark? How is the compression of the engine?
Click to expand...

Yup, new diaphragms.
it dosn't really run on the choke, it only fires a couple of times.
as i said the engine runs fine when i give it gas, and i can keep it going for as long as i want to. wouldn't a faulty float setting affect this?
spark is good as far as i can tell.

i haven't done a compression test, so this would be the next thing on the list. could bad timing also do something like this?


 
Do the compression test first. I do believe something is set up wrong in the carbs. If you have no problem above idle. And it seems to run okay at faster speed. Timing would not be an issue.
 
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