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1978 merc 110

M

mpknls

Member
my merc 9.8 runs rough at full throttle i just did a rebuild on the carb.. it runs great at half to 3/4 just gets realy nasty at full. how do i ajust the high idol
 
put a new one on came with the kit but it looked bigger so i put the old one back on. i did clean it out with a soft wire. pulled the entire carb down and cleaned could it be the carb its self it had a lot of gunk in it when i got it. the motor hung on a wall from 85 till now
 
You might have a bad coil--seen a lot of that of late. If so, it will run fine until you open her up. Way to tell is hold it wide open for a minute or so, then shut it RIGHT down and pull plugs. If one is black and oily, replace its coil.


Jeff
 
Does this carburetor have the black plastic arm on it for opening the throttle ??--------Is it broken ?------Is it adjusted properly ?
 
racerone said:
Does this carburetor have the black plastic arm on it for opening the throttle ??--------Is it broken ?------Is it adjusted properly ?
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yes it does and no it looks fine i have not touched the black arm but the mootor has all ways run like this at full open all last summer. thats why i did the rebuild. i have no clue how to ajust it. now i do know this motor was twined with another before i got it
 
kimcrwbr1 said:
Good point did you check sync after you installed the carb. WOT timing never needs adjusted if you didnt mess with it. But the primary throttle pickup is very important. I`m not sure on your motor but normally it takes a dial indicator and a multimeter to dial it in. First engine off put it in forward gear and advance it to WOT and check the gap between the throttle lever on the carb and the pickup cam there should only be between 1/32 to 1/64 inch gap it should not be binding. If the throttle lever moves more than 1/32 you can try adjusting it by earball. Take it back to slow and loosen the screw for the throttl lever and adjust it in a little at a time until you get the throttle butterfly to fully open without binding. I just checked my book and there is no primary adjustment just check the WOT gap between the cam and the throttle lever. Like racer says it may have got bent or is just worn out. I`m sure I have a metal one around here somewhere if you need to replace it or even a good plastic one.
high speed jets are as follows
0 - 2500 ft #41
2501 - 5000 ft #39
5001 and up #36
Do not run at low elevations with high elevation jets you will cook the motor
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LOL sync WOT all looks like something my kids would text to me lol im sorry im not that good with boat motors im learning. all we have around here is johnson dealers closest merc dealer is 2 hrs away sucks
 
kimcrwbr1 said:
My book gives no adjustment it is just fixed. With the engine off put it in forward gear and give it WOT. Take your finger and see how much space is between the throttle arm on the carb and the cam for the trigger plate. See if there is any wiggle up and down on the trigger plate. You may have not got the carb clean enough or possibly a bad ground for the coils. Pull the coils and with a small wire brush clean everywhere it grounds to the block and see if that helps.
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it is dark but i am a dedicated man LOL. i found that the coil has a wire that is not hooked to anything just laying there arking off the motor. i will fix that tomorrow
 
ok i found the small braided wire on the back of the coils cleaned a spot and attached both to the block. started in a tube of water and opened full open. sounds good ill put it on the water this weekend and give it a good test
 
racerone said:
For me these motors are elegantly easy to trouble shoot and repair.------------------Why would you give up on it ?
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im just one of them days LOL rebuilt the carb replace both coils tune up replaced the bafle plate and it still has a bad miss at full open. on topm of all that i get to my spot and it wont start pull pull pull puff pull pull puff! so i tap the carb and pow it cranks 2nd pull. run half open sounds good cut off and back to pull pull pull.......tap tap and away we go i dont know maybe the carb is just shot it was realy bad when i got it.... i noticed tonight when i was looking it over gas line was empty pumped up tight pull pull nothing sprayed with starter fluid pulled 3or 4 times and away we go. if anyone has any thoughts im open to try it
 
The float may be sticking closed. I've seen some of the earlier type Tillotsons (the type with the float top held on by 2 screws). The float was adjusted so high no gas came out until I lowered if a 1/16 inch.

If you have this type carb, remove the brass plug at the lower front (7/16 socket), then pump the bulb to see if gas flows out readily. If it doesn't, that's the problem.

Jeff
 
fastjeff said:
The float may be sticking closed. I've seen some of the earlier type Tillotsons (the type with the float top held on by 2 screws). The float was adjusted so high no gas came out until I lowered if a 1/16 inch.

If you have this type carb, remove the brass plug at the lower front (7/16 socket), then pump the bulb to see if gas flows out readily. If it doesn't, that's the problem.

Jeff
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no wrong carb. I have replaced the float when I did the rebuild done pulled the carb and went over the entire thing again all looks good like I said I can tab the carb with my leathermen and it will crank up.
 
i turned the carb upside down the lower arm that rides on the float spring is level. with the pin on the other side the float sping measure 3/32" above the top of the float im thinking the for some reson the needle is sticking
 
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