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1975 mercury 850 acceleration problem

J

jaspernonces

New member
hello, i just bought a 1976 fiber form runabout. it has a 1975 mercury 850 thunderbolt motor & mercontroller.
i took the boat out on the water for the first time, engine sounds like its running great, but i can't get over around 6 mph. i'm new to outboard motors, & after some research, it seems that the controller should go to around the 7 o'clock position, it stops at say the 9 o'clock,.. so am i right in thinking it's not getting to the full acceleration? what should i look for. I took the cover off of the motor & shifted the control lever full forward & full reverse. looks fine, but i don't know if it should go further? could it be something else? controller maybe?
 
Sounds like a stretched or maladjusted cable.
Does the shift cable shift gear and hold?I'm assuming it does as you get up and running.When you add throttle,does the throttle cable move immediately you move the shift arm past gear idle position?Does the distributor move and carbs open fully when throttle applied?
Is the warm up lever,the black one,in the down position and doesn't travel up as you increase throttle?
When you lift the warm up lever,does the cable move immediately?
What RPM's are you making?
If everything is ok then I would start with the basics,compression check,spark check,carburetor clean/rebuild.
 
yes it shifts gears great, and moves the distributor , the throttle cable moves as I advance it forward. just stops at the 9 o'clock position, boat only goes 7 mph ..I haven't checked the carb opening all the way, I'm assuming there's linkage between the distributor and carb.? the warm up lever doesn't move from down when I accelerate, but I noticed that if it's all the way up, and I push controller to 9 o'clock, it backs the warm up lever down, if that makes sense.?. I actually just landed in Japan, so I'm not with my boat, this is killing me though, not having my hands on it.
 
..."I haven't checked the carb opening all the way"

That's your next move. The spark advance STOPS before the carbs open all the way, with the top part of the distributor moving AFTER max spark advance is achieved (opening the carbs the rest of the way). Old grease inside there can get hard and keep it from moving (and opening the carbs). The solution is to heat that area with a propane torch and pump new grease into it via the fitting. (The best solution is to disassemble it and clean it, if you're adventurous.)

Jeff
 
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