73 mercury 500 50 hp throttle issue

davidmerc50 · Aug 5, 2012

i have a merc 500 i put new plugs in it new fuel pump kit rebuilt both carbs new inpeller and it runs good and idels good the only thing im have a issue with is when i go wot it bogs alittle and about 3/4 throttle the rpms build up and it will get on plane and everything but wot it will lose alittle power it acts like 3/4 throttle is better the wot any reason why this is doing that or should i not worry about it and its a tiller handle motor and the butterflys are opening all the way as they should help me please

Chris1956 · Aug 6, 2012

Re: 73 mercury 500 50 hp throttle issue

Sounds like the bogging from idle is a carb mixture issue. Richen them a bit. The high speed issue is likely a fuel delivery issue. Maybe the antisiphon valve is clogged or a fuel filter is clogged? Air leaks in the fuel line?

davidmerc50 · Aug 6, 2012

Re: 73 mercury 500 50 hp throttle issue

mine only has one screw and i adjusted them and no change and where is the antisiphon valve?

Chris1956 · Aug 6, 2012

Re: 73 mercury 500 50 hp throttle issue

One screw on each carb? Antisiphon valve is usually inside hose barb on built-in fuel tank fuel pickup fitting.

davidmerc50 · Aug 6, 2012

Re: 73 mercury 500 50 hp throttle issue

yes 1 screw each carb and ill check the valve and let you know thanks

davidmerc50 · Aug 6, 2012

Re: 73 mercury 500 50 hp throttle issue

it has a external gas tank so will i still have that valve?

Chris1956 · Aug 7, 2012

Re: 73 mercury 500 50 hp throttle issue

Portable 6 gal tanks do not have valve. Is vent open?

davidmerc50 · Aug 7, 2012

Re: 73 mercury 500 50 hp throttle issue

yes vent is open

michaud500 · Aug 8, 2012

Re: 73 mercury 500 50 hp throttle issue

I had the same issue. Check for air leaks!! Primer bulb!!!!!??

davidmerc50 · Aug 9, 2012

Re: 73 mercury 500 50 hp throttle issue

Did yours run good at 3/4 throttle but not as good at full throttle?

michaud500 · Aug 10, 2012

Re: 73 mercury 500 50 hp throttle issue

Same

davidmerc50 · Aug 10, 2012

Re: 73 mercury 500 50 hp throttle issue

i did find that my clamp was bad on the connector hat gos to the motor would hat be enough to make it run like that?

michaud500 · Aug 11, 2012

Re: 73 mercury 500 50 hp throttle issue

sure thing. Give a whirl post a report

davidmerc50 · Aug 14, 2012

Re: 73 mercury 500 50 hp throttle issue

ok i tried out my boat with anew clamp still the same thing any other ideals?

oldman570 · Aug 14, 2012

Re: 73 mercury 500 50 hp throttle issue

Have you replaced the fuel lines from the pump to the carbs ? They will go bad with age and the new enthol gas, and suck air or flak off on the inside and cause trouble. You might want to do a link and sync on the carbs and timming also.
Oldman570

davidmerc50 · Aug 16, 2012

Re: 73 mercury 500 50 hp throttle issue

ok i havent check the hose but whats link and sync its in time and the butterflys open alike is there something diff. that needs to sync?

oldman570 · Aug 17, 2012

Re: 73 mercury 500 50 hp throttle issue

New motors from the manufacture come with all the adjustable links set to the correct length needed for the best performance of the motor and should never be changed usually. The link and sync is the proccess done to get the carbs set to open up at the best time with the timming of the motor. A simple check of the setting is usally all that needs to be done anytime the carbs are worked on. JMO
Oldman570

73 mercury 500 50 hp throttle issue

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