Need Help with 1987 Mercury 50HP

[bpd119]

1987 Mercury 50hp 3cyl. I ran the motor in the pond for 2 days approx 10 hours with no issues. i topped off the premixed gas twice. the motor just recently starting bogging down it wont rev above about 2000 rpm. it will rev up most times when i have it in neutral and use the warm up lever. but when its in drive or reverse it has a serious bogging problem. i am not sure where to begin looking.

 

[seany150]

Re: Need Help with 1987 Mercury 50HP

i have similar issues with my 1985 7.5 merc. screams high in nuetral, but under load in gear completely gutless. I stripped and cleaned the carb, changes plugs, replaced a couple of gaskets on the cylinder water casing and exhaust casing and still the same. i've since switched the wires over on my coils and eliminated it down to what i think is a broken coil. i think under load it hasnt got enough oomph to produce a spark.

Maybe worth trying the easiest and simplest things on yours to try and eliminate what i could be. hope this helps a bit

 

[bpd119]

Re: Need Help with 1987 Mercury 50HP

ok thanks, i am going to start with the plugs i was doing alot of trolling and maybe they got gummed up

 

[sportsmanphil]

Re: Need Help with 1987 Mercury 50HP

The fuel we buy now days will be 10% ethanol. Older OB's are not friends with this gas. It has a tendency to damage rubber and plastic components in the fuel system, from the inlet needles, floats, check valves in the fuel pump and even the valves in the primer bulb.

Ive opened this can of worms on my own OB and have not worked through all of them yet. There are some revised parts available that are alcohol (ethanol/methanol) safe.

 

[bpd119]

Re: Need Help with 1987 Mercury 50HP

i do understand about the gas but it was working fine and then all of a sudden stopped, is this the symptoms it usually has with the ethanol problem?

 

[sportsmanphil]

Re: Need Help with 1987 Mercury 50HP

Its possible, just wanted you to consider the possibility.

About a week ago I learned of a TSB for fuel pump vacuum. Mercury wouldnt give me the TSB but told me about it. A poster here was kind enough to find it and post a link. You might be able to search it out with "TSB" if not I can post the same link.

 

[bpd119]

Re: Need Help with 1987 Mercury 50HP

yea if you could post it that would be great

 

[This_lil_fishy]

Re: Need Help with 1987 Mercury 50HP

I had the same problem with my '86 50. Typically it's just not firing on all cylinders. Check your plugs first, if I spent extended periods at idle (which I do a lot of) it would foul the top plug. So that's where you start, then rebuilding the carbs, fuel pump, and re-adjusting the carbs should do the trick. I also found that running it near empty cause a lot of problems like this as I have an auto-mixer that would just load it up with oil if it ran dry on gas.

Of note, when rebuilding the carbs be sure to get new floats, needles and seats. As the foam floats/rubber tipped needles don't work very well at all and can cause a world of headache. The carb kits do not include the floats and seats, so you have to order them seperately.

All in all, all of the above cost me less then $100 in parts and took a couple of days to get just right.

Ian

 

[verado7]

Re: Need Help with 1987 Mercury 50HP

check for spark on all cylinders - a common mode for the classic fifty is to lose 2 cylinders on the switchbox - how does the exhaust sound when running on muffs - does it still have that grunty pop to it ?