84 50hp. mercury with no top end . HELP!!!!

[trpm74655]

I have a 1984 50hp. merc on a pontoon boat. The problem is I can only get about half speed under load. Have had the boat and motor since they were new . I put it in the shop twice in the last year and they cant find the problem. I have checked fuel system , carbs, compression and have spark on all four cylinders. Have been reading from this board and think it may be the high side windings on the stator. Checked impedance between red and red white and got 0 ohms ,full closed circut.<br />Would apperciate any help.<br />Thanks Rex P.

 

[DUTTON]

Re: 84 50hp. mercury with no top end . HELP!!!!

I had the same problem with my 50 merc,it would not reach WOT, it turned out to be the ignition box. Replaced it and it runs at 5500 rpm's Your box and or wires may be breaking down under load. Is the prop slipping?

 

[trpm74655]

Re: 84 50hp. mercury with no top end . HELP!!!!

Thanks for the reply Dutton , I have checked the prop. BUT I made the mistake of taking the shops word that the fuel system and carbs had been fully checked. Took the **** thing apart my self and found bottom carb was way out of adjustment and throttle linkage between the carbs was split. It is fireing on all fours now .Going to put it in the water tomarrow and see how it runs now.<br />Thanks agian REX P.

 

[trpm74655]

Re: 84 50hp. mercury with no top end . HELP!!!!

Well i put the piece of junk back in the water today and it is still bogging down after about 1/3 to 1/2 throttle. Only duz this under load . Any help would be welcome Rex P.

 

[corm]

Re: 84 50hp. mercury with no top end . HELP!!!!

pull off the top 2 plug wires to see if it is running on the bottom carb, or put some gas & oil in a squirt bottle and shoot some in the carbs to see if it picks up some rpms.<br />if so it is the fuel sys. Pumps maybe, try squeezing the primer bulb to see if it runs more RPMs. If you pull off one plug wire and get no change you could have a bad plug or switch box, the coils usually don't go bad on these motors.

 

[trpm74655]

Re: 84 50hp. mercury with no top end . HELP!!!!

Thanks for the reply Corm. I pulled the plugs one at a time a couple of days ago and found the two for the bottom carb had no effect on the motor. Checked and found the throttle linkage between the top and bottom carb (which is plastic) was split. I replaced the broken linkage and now if any one of the four plugs is puled it effects the motor. I tried spraying fuel from a squirt bottle into each carb one at a time and neither increased the rpms. Tried pumping bulb and still no change . Running out of options. This may sound like a stupid question but are the throttle on top and bottom carbs susposed to be in alienment with each other ? Because when I replaced the linkage between the carbs I lined them up like I would on a set of carbs on a motorcycle. Any Ideas would be welcome.<br /><br />Thanks: Rex P.

 

[corm]

Re: 84 50hp. mercury with no top end . HELP!!!!

Hi,<br />You set the carb butterflys right.<br />As for the bog problem I am at a loss.<br />Maybe the high speed stator is bad and not producing enough power to fire the plugs.<br />Causing it to not burn the fuel to reach top RPM.<br />corm

 

[kev_79]

Re: 84 50hp. mercury with no top end . HELP!!!!

I would rebuild the carbs, if you already haven't. I had a prob very similar to yours and it turned out that their was a gasket between the bowl, and the passage where fuel from the main jet came out. It was smashed, and old, so when it started to switch over to the main jet for power, it would bog down. As for the first 1/4 throttle, you couldn't tell anything was wrong. I would try this first, since I think the gasket kits for the carbs are something like 4 bucks a piece. Just pray stator is good, becuase it can be a job changing (getting flywheel of sometimes a real *****), and to have freshly rebuilt carbs can't hurt you cause. Good Luck, tell us how it goes.

 

[trpm74655]

Re: 84 50hp. mercury with no top end . HELP!!!!

Thanks for the replies Corm and Kev_79. I will check the carb gaskets and hope its not the stator! Anybody know the numbers for the ohms test for the stator? And you check between red and red/white for high side?<br />All and any help is very welcome!<br /> ( 1984 50 hp. 4 cyl. Mercurcy )<br />Thanks Rex P.