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taking carb off early 80s merc 9.8

T

tsunami14

Member
hi guys, i\m baaack lol. i am into a project and am happy that i was able to change out the impeller nad get the water pumping again, but this new to me merc 9.8 (serial A700688)bogged big time on going to higher throttle and got tougher to start and i ended up rowing to shore (forgot to take my electric with me ... bummer).
anyways i have a couple questions if u can help me.
1. can anyone tell me the spark plug & gap i should be using? the current ones are corroded on the outside, and i don't know if the previous owned had the right ones in, who knows
2. how do i get the carb out? i see the choke goes through the lower part of the cowling, how the heck do u disconnecct that?
3. the insulation of the cowling on another motor i have is turnign to dust nad i am certain will get into the carb. can i just scrape that insulation foam off and leave it like taht ? will it melt the colwing if i don't replace it with something, and if so, what can i put on there? i know it will be louder, but i can live with that (at least i say that now )
thanks guys, appreciate it very much
 
hi i found the plug on the inet, the original was the correct one but i am replacing it anyways. still don't see how taht choke cable gets disconnected from the choke . maybe just disconnect at the swivel on top of the carb, that might work.
 
Easy, just take the screw out on top of the carburetor.----------Take that foam out of there so it does not get into the reed valves.-------------No the cowling will not melt down if you do that.
 
thnaks racer i;ll happily scrape that out . i can see how it could easily foul everything up.
merc 7.5 carb.jpg
here is a pic of the top of the carb (I might not be much of a mechanic but I can upload a pic lol) some corrosion is evident but i can buff or carefully scrape that off.
the two mechanisms that need to be disconnected are the black plastic. on the choke it is a nut (you said screw but on this model is a nut)
also is the throttle control mechanism just beside the choke nut. it has a small nut and phillips screw on the other side . i'll have to take them off as well, i am wondering if this is something i can get back together again?

( i am taking this carb out to drain gas out and reinstall and do the seafoam pump in. is there another way to get the seafoam in easier than removing the carb? i wouldnt think so , but that throttle mechanism has me thinking)


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racerone said:
Easy, just take the screw out on top of the carburetor.----------Take that foam out of there so it does not get into the reed valves.-------------No the cowling will not melt down if you do that.
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is there another way to get the seafoam in easier than removing the carb?
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Drain the carb or run it until it is out of fuel. Remove the fuel hose from the tank and drain it. Stick the tank end into the can or pour some into a clean container and stick the hose into it. Then use the primer bulb to pump it into the carb.
 
guyjg said:
Drain the carb or run it until it is out of fuel. Remove the fuel hose from the tank and drain it. Stick the tank end into the can or pour some into a clean container and stick the hose into it. Then use the primer bulb to pump it into the carb.
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hi guy, thanks for your reply. how do you drain the carb? i used this method u suggested on another carb, but i removed it first because i don't know how to drain it in place.
by the way, your method worked great. had the motor purring two days later with a few minor adjustments. thx
 
guyjg said:
Disconnect the fuel line and run the engine w/muffs until it runs out of fuel.
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i wish i could, now it won't start and i can hear some air in the fuel tank when i squeze that primer ball a dozen times and it still does harden up. no gas is getting to the fuel pump o nthe carb. i even changed lines on the same tank, same sounds of air when i squeeze the ball. then i changed tanks, same sound. do u think maybe i have a leak in the two fuel lines in the carb. i have some new fuel line i'll replace them tomorrow and see what happens. i don't know, i tried two tanks and two fuel lines with primer bulbs and no action but sounds of air into the carb. i might have to break down and buy new tank and fuel line / primer tomorrow as well. thx for the tip on running it dry, yes that makes emminent sense, sensei.
 
The plastic part on the throttle shaft often is broken ---inspect carefully.---------Screw or bolt on the choke --same idea.-nothing to be scared of at all.
 
racerone said:
The plastic part on the throttle shaft often is broken ---inspect carefully.---------Screw or bolt on the choke --same idea.-nothing to be scared of at all.
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racer, np with the nut on the choke, but if i back out the screw on the throttle device will that loosen something inside the carb? looks like maybe a pin might drop down?
 
ha upon further inspection i see that throttle gizmo is not connected to anything but the carb itself, its top end serves as roller as the throttle is turned. np now to get that off. and, i see the fuel line a t the exterior connection end is wet and all around it, i think it leaked and that would maybe cause a lack of power and ultimately the whole engine just spitting along until it wouldn't run? new line for it tomorrow :), and then a comforting seafoam bath !
 
hi i cant tell from the old fuel line there is no printing on them, what is the diameter for the 85 merc 9.8 and merc 7.5 fuel lines. i cant find it in the seloc manual i ahve either. thx
 
racerone said:
The plastic part on the throttle shaft often is broken ---inspect carefully.---------Screw or bolt on the choke --same idea.-nothing to be scared of at all.
Click to expand...

hey racer, i took that carb off (mostly) and ten discovered a small plastic line connecting hte back of the carb to some other thing on the block it looks like . how to remove that piece without crunching it up. just use fingers and wiggle it, gently with needle nose? i was surprised to see that line as the manual i have makes no mention of it.
thx
by the way i disconnected the fuel filter cover to release the fuel line. there was a fair amount of particles in there. will that filter fall off of it's own volition?
thx again
 
hi guys , i have been away on holidays but before i went i was successful in draining the seafoam out of the carb of my merc. i am looking forward to running it once i get back home. question though: when the motor bogged down and died out on the lake, it sounded like something was still spinning in the powerhead and then slowly stopped, and sounded like a gear / teeth ticking against something slower and slower until inertia was all gone and it quit spinning. i have never heard this before on any engine that quit. any ideas what this might have been? thx
 
tsunami14 said:
hi guys , i have been away on holidays but before i went i was successful in draining the seafoam out of the carb of my merc. i am looking forward to running it once i get back home. question though: when the motor bogged down and died out on the lake, it sounded like something was still spinning in the powerhead and then slowly stopped, and sounded like a gear / teeth ticking against something slower and slower until inertia was all gone and it quit spinning. i have never heard this before on any engine that quit. any ideas what this might have been? thx
Click to expand...


My 9.9 makes the same noise if it dies while IN gear.

Your problems sound a helluva lot like mine. Major 3/4 throttle + bog, no ability to chew threw weeds (just bogs right out and shuts off). Became increasingly hard to start, eventually won't run worth a damn at all.

First, I cleaned my carb. INCREDIBLY simple on this engine. Fortunately my carb was spotless. Being dumb, I ignored the fuel pump diaphragm (more on that later). I took the boat out, still ran like crap, but it ran better than before. Got about 3 weeks of use while waiting for a carb & fuel pump rebuild kit before it ran even worse than before.

Pulled the carb, this time took the fuel pump apart and wow...major globs of separated oil in there - fortunately it is easy to clean. Then I took the carb apart just in case...still clean. So I went back to my fuel lines, both before & after the fuel filter. HOLY crap. I already cleaned my filter once, it didn't have much crap in it - but it still wasn't pretty. However this time around...it was LOADED with gunk. So I cut open my fuel lines and there was enough black gunk in there to butter up some bread and make a sammich. Drained my fuel tank, inspected my tank lines and primer bulb, everything is clean.

Took it back out to the lake & it didn't run any better. Tore it back apart and noticed all my vacuum lines were either collapsed, plugged with goop or leaking. Replaced all 3 lines and BAM. Finally started first pull, no more irratic idle and sounds as healthy it did years ago....
 
heckhole said:
My 9.9 makes the same noise if it dies while IN gear.

Your problems sound a helluva lot like mine. Major 3/4 throttle + bog, no ability to chew threw weeds (just bogs right out and shuts off). Became increasingly hard to start, eventually won't run worth a damn at all.

First, I cleaned my carb. INCREDIBLY simple on this engine. Fortunately my carb was spotless. Being dumb, I ignored the fuel pump diaphragm (more on that later). I took the boat out, still ran like crap, but it ran better than before. Got about 3 weeks of use while waiting for a carb & fuel pump rebuild kit before it ran even worse than before.

Pulled the carb, this time took the fuel pump apart and wow...major globs of separated oil in there - fortunately it is easy to clean. Then I took the carb apart just in case...still clean. So I went back to my fuel lines, both before & after the fuel filter. HOLY crap. I already cleaned my filter once, it didn't have much crap in it - but it still wasn't pretty. However this time around...it was LOADED with gunk. So I cut open my fuel lines and there was enough black gunk in there to butter up some bread and make a sammich. Drained my fuel tank, inspected my tank lines and primer bulb, everything is clean.

Took it back out to the lake & it didn't run any better. Tore it back apart and noticed all my vacuum lines were either collapsed, plugged with goop or leaking. Replaced all 3 lines and BAM. Finally started first pull, no more irratic idle and sounds as healthy it did years ago....
Click to expand...

hi that is great info alright. could you please let me know where those vacuum lines are located? i think there is one at the back of the carb, but that is all that i noticed. and where would a guy buy those lines, and what size are they\? thx again for the post, most enlightening !
 
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