Mercury 50 runabilty prob

[convincer253]

I have a Merc 50 4cyl serial number 5797774 1980/81. My problem is the engine will only run with the choke on and will not idle. I've rebuilt the carbs/fuel pump/compression is 130 to 135 I've also ruled out primer bulb gas tank and connector. with it running I can spray carb cleaner everywhere without the engine rpm changing showing me there is no leaks. the guy that had it before me changed out the switch box and maybe the coils. I dont know where to go next....Help please!! Is there a way to do a static sync and link?

 

[Barnacle_Bill]

Re: Mercury 50 runabilty prob

5797774 is a 1980/81 model. That is symptoms of a bad fuel pump. have you done a compression check?

 

[jody4437]

Re: Mercury 50 runabilty prob

Hello, thanks for reply.We convincer and i are working together on this 50hp
motor.we have rebuilt carbs,fuel pumps,did compression check and results were 130 to 135lbs at each cylinder.We removed fuel conection and went right to tee between carbs.We can keep it running if we pump fuel bulb.However when we rebuilt the carbs we did notice one float had a bent ear,the other was flat across straight.Convincer thinks maybe it running out of fuel when motor dies...leading toward float height.Is there any other reason this could be happening?

 

[jody4437]

Re: Mercury 50 runabilty prob

We adjusted float hieght motor runs with out priming bulb to keep running.Still having to choke to keep running and will only run at a higher idle with choke 3000rpm(will not idle at all with or with out choke).could this be a sync and link problem? manual says to sync you need to have in water and in forward at idle to sync. Is there a way to sync with out running to start at??.
any help would be appreciated thank you!

 

[jody4437]

Re: Mercury 50 runabilty prob

Okay here's the update ....we got in running like a brand new motor things we found..behind power pak was a bleed line rotted we replaced.In cleaning of both carbs we fail to clean the long needle that goes on angle toward bottom of bowl alowing air to bowl.What a huge miss after we clean the carbs eight times lol... we removed this needle and found pluged hole..
Long story short take carbs completely apart.. well hope this helps someone else. Our lost time your gain,but a huge experiance in life thank you..all

 

[fishyfingers]

Re: Mercury 50 runabilty prob

thanks for all the info. It is helpful and leads me to believe I have a similar dilemma. The motor is a MERC 500 1969 50hp. It starts and idles great... Goes great at slow to moderate speeds... but when I really get on it... It loses fuel pressure and slowly fades back to a slower speed with throttle still wide. If I pump the bulb while I drive it will keep running at full throttle. The hose looks good and I checked most of the visible connections. Any ideas?

Maybe vacuum or pump????
The motor was rebuilt last year. Please see attached thread:

http://forums.iboats.com/showthread.php?t=240645&highlight=same+question

Thanks for any advice or ideas!!