Help! Can anyone tune a merc 2.5 motor by Thursday night???

Rain City

Rain City

Crew Member
I've pulled apart this carb a few times now and can't keep her running. Last year the jets were all bunged up so I cleaned them but in the process messed up the float in some way. I think it's running too rich now. The thing never used to run great either way. Doesn't like a low idle. Any help would be appreciated. This is the carb. 20220712_184622.jpg
 
Did you try poking a fine piece of wire in the main jet? Like a piece off of a wire brush. I just YouTubed the rebuild for my Honda 2000. That was the ticket on that carb.
I just tried doing a 9.9 2 stroke. Put a kit in it, and no love. Gave it to my friend who was a licensed marine mechanic. He said this was the trick. Had it running in no time. He said air and cleaner just doesn’t do it sometimes.
Good luck.
 
Coyote Spooner said:
Did you try poking a fine piece of wire in the main jet? Like a piece off of a wire brush. I just YouTubed the rebuild for my Honda 2000. That was the ticket on that carb.
I just tried doing a 9.9 2 stroke. Put a kit in it, and no love. Gave it to my friend who was a licensed marine mechanic. He said this was the trick. Had it running in no time. He said air and cleaner just doesn’t do it sometimes.
Good luck.
Click to expand...
I haven't but I'll give it a whirl. Thanks
 
If you don’t already have grab yourself a can of carb cleaner when you do the jet cleaning. Works great for taking the wax off the needles and jets. Pay close attention to your float needle valve make sure the tip of it is clean and your float and spring are moving freely. Use the carb cleaner make sure you have good flow through all ports. Todays gas is horrible stuff and our carbs need regular cleaning to keep the waxes out. Don’t be afraid to open that puppy up and get at the guts of it. Carbs look intimidating but there’s really not a lot to them. I’m sure your more than capable of stripping down and reassembling that puppy.
 
get some welding tip cleaners. They come on one tool with a ton of sizes. Poke them through the jets.

also, most carb cleaners aren’t that corrosive now a days so they don’t work that well. I got a jug of stuff that gets put in a bag on top of the sealed container because it’s that nasty. You need to find the good stuff or soak for a long time if using regular carb cleaners
 
Rain City said:
I've pulled apart this carb a few times now and can't keep her running. Last year the jets were all bunged up so I cleaned them but in the process messed up the float in some way. I think it's running too rich now. The thing never used to run great either way. Doesn't like a low idle. Any help would be appreciated. This is the carb. View attachment 82221
Click to expand...

Doesn't it need to be stuck to an engine? Hmm.
 
Ok fine, pull the plug first and see if it is fouled. You'll know in 3 seconds based on how the plug looks if it's lean or fouled. Bummer I'm not in town but I have a gunson color tune in the garage at home that makes tuning a snap.

I've never laid hands on a carb like that but the float manages fuel level in the bowl and determines rich / lean as you know. Then you can speed the carb up once you get the float level correct. Did you mess with the float level? It's one carb so you should be able to take it back to basics, particularly by first checking the state of the plug.

Oh ya, soak the **** out of it in carb cleaner as smarter people above have already stated.
 
I can't really tell, but how do you level the float, is there a mark on the fuel bowl? For example, the GD su's I deal with need the float level set about 18mm from the bowl. It is an epic pita but so critical to get the fuel level correct. Then there is a big screw to set mixture and so on. You only have one carb to manage so if you never messed with the float level before and the plug shows which way its running, then slap it back together, carb clean the **** out of and go for a 4 knot Italian tune up.
 
I think I made some headway. So like I said before, i had fully poked, picked, soaked, sucked, blown and blasted the whole thing including all the little bits and bobs last year. I haven't put any time on it since because I screwed up the float adjustment so bad it wouldn't run. Just puked fuel all over the place. So now, two days before leaving for a trip, I decided to take a crack at finishing the job. Adjusted the float (thanks @noluck for explaining me through that). Started it but it wouldn't stay running. Then @Reeltime pointed me to the adjustment screw that they bury behind the brass plug. Started messing with that next. Got her going but couldn't get the idle down without it dying. So now I'm pulling the carb off and putting it back on over and over and over and over again trying to adjust things. No less than three times did I forget one or two the six steps to getting it off. Each time cursing the little overflow tubes that have to fit through the NASA tolerance holes in the bottom of the case. Stopped again to get gas. Stopped again to get a lamp and some bug spray. This all seemed insanely difficult just to make some minor adjustments each time. Then finally at 10:45 PM @Reeltime asks, "can't you just take the fuel tank off to access the adjustment screw?"... Kill me. Back at it tomorrow to make some adjustments WHILE IT'S RUNNING!
 
Had an issue like that took it in the mechanic said happens all the time with small mercs, some micro hole in the carb gets plugged, the soak it in solvent and was good to go
 
SpringVelocity said:
The infamous low idle jet. If it's dying low idle it's clogged. In a yamaha there is a small brass jet. It's a POS. Probably same as merc. Remove it and blow it out.

Here is a video

Click to expand...

This, SV is on it. Find the spec for your float height and set it. There’s usually three circuits on a carb, low, mid, and high. The main jet only comes into play when you’re wide open. Its not going to affect your idle. Also the main jet is the biggest passage in the circuits, idle is the smallest and first to plug, one needs lots of fuel one needs little. Look for a passage (might have a jet might not) that goes from the bottom of the carb (with the float bowl off) to the Venturi (engine) side of the carb. Spray carb cleaner in all the little ports on the bottom of the carb with the bowl off. One of them should let the carb cleaner spray out another port on the engine side of the throttle butterfly. It’s meant to deliver fuel when the throttle is closed while rpms and vacuum is low. Not to be confused with the choke butterfly which will be closer to the air intake side than the throttle butterfly. That’s your idle circuit, poke and clean the **** out of it. You can usually get clues about where a passage starts and ends by looking at the casting of the carb body and tracing from port to port if that makes sense.

Did it ever run good? If so you don’t need to start tweaking hidden ****. It’s a common first response but if you think about it doesn’t make sense. The adjustments didn’t change themselves, something else is happening you may cover it up for a while but that’s all you’ll do. There’s rarely a need to tweak a carb on an unmodified engine.

If you really wanna start tweaking first step is count the turns from where it’s at until it’s gently seated closed so you know where to go back to when you fix the real problem!
 
Last edited:
triplenickel said:
This, SV is on it. Find the spec for your float height and set it. There’s usually three circuits on a carb, low, mid, and high. The main jet only comes into play when you’re wide open. Its not going to affect your idle. Also the main jet is the biggest passage in the circuits, idle is the smallest and first to plug, one needs lots of fuel one needs little. Look for a passage (might have a jet might not) that goes from the bottom of the carb (with the float bowl off) to the Venturi (engine) side of the carb. Spray carb cleaner in all the little ports on the bottom of the carb with the bowl off. One of them should let the carb cleaner spray out another port on the engine side of the throttle butterfly. It’s meant to deliver fuel when the throttle is closed while rpms and vacuum is low. Not to be confused with the choke butterfly which will be closer to the air intake side than the throttle butterfly. That’s your idle circuit, poke and clean the **** out of it. You can usually get clues about where a passage starts and ends by looking at the casting of the carb body and tracing from port to port if that makes sense.

Did it ever run good? If so you don’t need to start tweaking hidden ****. It’s a common first response but if you think about it doesn’t make sense. The adjustments didn’t change themselves, something else is happening you may cover it up for a while but that’s all you’ll do. There’s rarely a need to tweak a carb on an unmodified engine.

If you really wanna start tweaking first step is count the turns from where it’s at until it’s gently seated closed so you know where to go back to when you fix the real problem!
Click to expand...
I'm going to start fresh and try and understand the whole thing better this time. The engine ran well for the first 10 hours and then immediately started having low idle issues. I'd have to get it to almost die before shifting it into drive so I wouldn't keep hammering it into forward. Always needed a little choke to stay running. Mind you, I never put any real maintenance time into it. I only ever used it once a year on our bigger cruises, flushed it and put it away. Probably could have used a little more love along the way.
 
SpringVelocity said:
The infamous low idle jet. If it's dying low idle it's clogged. In a yamaha there is a small brass jet. It's a POS. Probably same as merc. Remove it and blow it out.

Here is a video

Click to expand...
Where was this video a year ago?!!!
 
Rain City said:
I've pulled apart this carb a few times now and can't keep her running. Last year the jets were all bunged up so I cleaned them but in the process messed up the float in some way. I think it's running too rich now. The thing never used to run great either way. Doesn't like a low idle. Any help would be appreciated. This is the carb. View attachment 82221
Click to expand...
PM Sent
 
I had the same issue recently. Pulled the carb and brought it to maple marine in Langley. Paid cash and the guy rebuilt it by the next day and it worked fine - I had a fishing trip the next week. Pretty tight for you now but might be worth a try.
 
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