77 mercury throttle problem

M

moparkid16

Cadet
Joined
Jul 31, 2012
Messages
16
i have a 77 mercury thunderbolt 500 50hp engine. i was told it ran good when i bought the boat. i finally got it to run, but when you move the gear shift all the way forward, it does not rev the engine till at least 30 seconds after. and it barely revs the engine at that. the prop spins, and you hear a clunk when puting it in gear, both forward and reverse. when i put it in reverse, the engine revs very high. i do not have any experience with out boards, as this is my first boat. im guessing the linkage in the motor needs adjusted, but dont want to mess with anything till i get advice from someone who may know what it is.
 
hotrod53

hotrod53

Chief Petty Officer
Joined
Oct 16, 2009
Messages
508
Re: 77 mercury throttle problem

Sounds like your cables or adjustments are jacked up. There are 2 cables, one shifts FWD-N-REV, the other is throttle. Sounds like when you shift to REV, the throttle is pulling too, when you shift to FWD, the cable is not pulling throttle. I'm guessing that the cables are not in sync but unfortunately I'm not experienced in adjusting them. Actually, mine need adjusted too.
 
M

moparkid16

Cadet
Joined
Jul 31, 2012
Messages
16
Re: 77 mercury throttle problem

also, when i put the shifter all the way forward, while having the throttle all the way up, the throttle moves back down about an inch. when it does that, i can move the shifter a hair bit forward and thats where i hear the engine start to rev up a tad. is this because of the linkage hitting each other causing the throttle to go down when goin forward on the shifter? the shifter seems to go forward alot more than it should, but with no experience, im not sure on that. there is a knob that turns on the bottom front of the shifter throttle assembly. what is that?
 
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