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please help ! 1971 merc thunderbolt mercontrol box ?

B

bama221989

Member
Well today me and my dad replaced the fuel line, couple raggedy wires , and took off the lower unit to put a new impeller on to get my boat running that my grandpa gave me
The motor is a 1971 mercury thunderbolt 500 50hp 2 stroke 4cyl
Every thing went awesome and now there is a constant flow threw the pee hole

Now to my question
I noticed last time when i took it out their was next to no trottle when engaging into gear , i had to press yhe lever all the way to the floor to get it to go and it wasnt fast speed at all (from the other times i took it out when i was younger ) so basically i had maybe an inch of lever to give it gas ?

So i took the orginal merc control unit off and opened it up , everything was intact and looked functional , put it back together after some cleaning and still the same thing

So im wondering if their is a tension cable or something ?

Im new to this so please excuse my lack of knoledge any help is greatly appreciated !
 
Could be worn/stretched cables. Have someone shift gear while you watch the cables at the engine side a see how much travel the shift lever has before the throttle cable starts to move.Adjust the cable like kimcrwbr1 says and if you run out of adjustment replace cables.
 
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i think you have a grease fitting on the distributor to advance timing....if so it may be bound up...
 
Maybe the motor is only running on 2 cylinders ??----------Check for spark on all 4 leads.-------Test compression .-------------Clean carburetors !!!
 
Thank you all for the awesome advice here now ab to put new plugs / wires / fresh gas and oil
The mercontrol box didnt have shavings in it and i did see the plastic bushing inside (which i just ordered ) because the one in there now felt brittle
 
Keep an eye on the wee spring loaded dowel,marked E,it can jump out and is damm hard to find :D Take my word for it
 

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Just to be 100 percent , i bought a 16fl oz quicksilver 2 stroke premium oil the chart reads

16:1 48 oz for 6 gallons ? So i need to go buy a big jug and measure out 48oz for each 6gallon tank
 
?????-----I think there is something wrong with the math here-----big time wrong !!-------------Mix gas and oil at 50:1 here.
 
It was on the bottle it had diffrent ratios on the bottle , ot was in marine section quicksilver premium 2 stroke by mercury, guess it can be used for chainsaws and lawn mowers also
 
Hello. Per your photo - "C" is for what? I have been trying to find out that this plug is for. See image above. Thank you!
 
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50:1 is 16oz to 6 gallons it sounds like you have the throttle and shift cables mixed up (as previously stated) the shift moves first then the throttle cable.
 
If you are going to buy new mercontrol box from dealer i can tell you my story. Well i bought new control box for my 1977 20hp Mercury. Dealer asked me questions about my engine, and sold me new box, which is for manual start engine, since i have no electric start. New box works well, but i can only use it for throttle, i cant assemble gear cable since this new control box works "wrong way". I mean, if i push forward throttle, engine will rew up but, it will go reverse gear. So gear is working wrong way. Anyway it is not big problem to me, i can put forward gear when leaving, by hand, and i can adjust throttle with remote control. Also i like new feature, with this new control box i can switch off and on the ignition system.
 
Evinrudemen said:
If you are going to buy new mercontrol box from dealer i can tell you my story. Well i bought new control box for my 1977 20hp Mercury. Dealer asked me questions about my engine, and sold me new box, which is for manual start engine, since i have no electric start. New box works well, but i can only use it for throttle, i cant assemble gear cable since this new control box works "wrong way". I mean, if i push forward throttle, engine will rew up but, it will go reverse gear. So gear is working wrong way. Anyway it is not big problem to me, i can put forward gear when leaving, by hand, and i can adjust throttle with remote control. Also i like new feature, with this new control box i can switch off and on the ignition system.
Click to expand...
I understand people are bored but this is a 4 yr old hi jacked thread.
 
??----Evinrudeman----Did your dealer forget to explain to you about the kit needed for the shift cable.-----You just need some bits to make it work !!
 
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