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Getting a 1973 mercury 850 thunderbolt control box to work right

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Dennyac

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Ok I'm trying to fix my boat when I move shift lever forward it runs like it should be in reverse speed doesn't throttle all the way. But when I move shift lever back it reevs hi but doesn't engage prop. I have only disabled control box and pulled lower unit. Now I understand you can mess up gearing in lower unit. But forward should be gas forward correct? Please any thoughts
 
Please any help would be appreciated, forward is supposed to go forward so do I need to change something else? Screenshot_2020-04-13-00-35-14.jpg
 
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It should move the whole distributor cap on forward and reverse but it's only slightly moving on reverse where do I need the shift cables on engine and what should the control box be set at when reassembled. Apparently the throttle cable moves the distributor cap so I need it set first it can't throttle all the way because it's set wrong I'll play with it more tomorrow.
 
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Ok I'm having a hard time still I'm sure I'm over thinking this how do I line up throttle on motor with control box. Please some adviceScreenshot_2020-04-13-02-57-24.jpg
 
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STOP-----Do not adjust anything if you are not sure of the results.------Remove lower unit.-----Put lower unit in neutral.-----Put control in neutral.-----Reassemble.-----Test run-----Throttle is limited in reverse.----There is no need for full throttle in reverse !
 
Not trying to get full throttle in reverse lol. Its forward that I'm not being able to work. But I am doing it all now getting things in level
 
Ok this is how throttle sets on full forward shifter and throttle. Ok won't let me upload the picture. on full forward on shifter and full forward on throttle it doesn't go all the way on throttle. But if I move the shifter all the way to reverse with throttle handle to ideal it full throttles at the engine. That sounds reverse of what it should be
 
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First check that you have the cables installed correctly: the shift cable moves first - then the throttle cable. The shift cable goes on the bottom and the throttle cable goes above it, the shift cable goes on in neutral with the motor in neutral850-controlsetup.jpg
 
There is a warm up lever ( throttle only ) on most control boxes.------The big lever shifts the motor and then applies throttle as you push it further.----Post pictures as that will help explain what is going on.----Did this problem develop suddenly ??
 
Ok the boat didn't run at all give me a few putting on lower unit now I believe it throttles high when you pull back because that is actually forward. And moving the shift forward is reverse not sure why. I regeared the lower unit so when you pull the lever back it engaged the forward
 
Ok that's it that's why I keep running into a wall pulling the main lever backwards now engages the foward and pushing the main lever engaged reverse. From ever video I saw forward is forward. But for some reason this control box is reverse. Now I'm am tuning neutral and making sure shift cables move before throttle. Give me a few to synchronize every thing and I'll re post
 
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Explain what you mean by -----" I regeared the lower unit "--------Something is wrong here and the more adjusting you do , the worse it might get.-----Till something breaks.
 
Ok I had a problem from get go when I move the shift lever\throttle the main one not the warm up level it would go forward but not fast at all. I tried to move the smaller warm up lever and it still maxed. But when I moved the main lever backwards it would rpm high. I changed the gear in lower unit to match that just now forward. On main lever now engages the reverse and won't throttle high. And natural is now dead on now if I move the main lever backwards it engages the forward and will let me if I push all the way down it Will give full throttle to forward
 
I don't think y'all are understanding what I'm trying to explain but none the less it works. Have you ever seen a controller that pulling it towards engine it engages forward? If that's not normal at all I'll need to order a new one
 
Sierra 18-3317 again sorry for the confusion and thanks for all your help you tried to give. Now it's time to start sealing the gear case. The old pump most seals were shot
 
Use soap (not grease) to help get the impeller in. Grease the driveshaft splines before you install it and these instructions will help :
Turn the LU shift shaft by hand counter-clockwise until it
stops, then with Vise Grips tight on the bottom of the shaft turn it a
few more degrees CCW until it clicks into a stop, this
should be neutral - check by turning propshaft --
prop should spin freely.
Put control in N and go ahead and attach LU to driveshaft housing some turning of the flywheel will help the DS splines align.
Do not shift into reverse unless you turn the prop at the same time.
 
Ok thanks a million guys I know your time is valuable. So it means alot you took the time to listen. The seal at the bottom of the water pump was shot. I use soap on all the seals for water pump correct? Oh one last question how do I know what propeller to replace with.
 
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No use some gear lube on the seals, prop depends on weight of boat and gear [eg. 16' boat with 250 lbs of fuel etc. could use a 21" pitch]; the only way to accurately determine which prop to use is with a tachometer the motor should run between 4800-5500 rpms at full throttle. I like to be near 5500 at full throttle. The weight should be on the Coast Guard information tag in the boat.
 
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