Rebuilt carbs wont go fast merc 45 1987

[pdehardon]

I rebuilt the carbs on a 1987 Merc classic 50(45hp). It idles of for a minuet then stalls. however if I tap the choke when it slows down I can keep it Idleing. Also it only goes 3000rpms at WOT unless I pump the prime ball then it revs up to 5000rpms. Adjusting the mixture does not seem to help. <br /><br />Question 1:<br />How do you set the Carb float level?? I could make no sence of the Merc service manual. Could having the float too tight cause my problem?<br /><br />Question 2:<br />The rebuild kit included 2 diaphragms one of rubber and one of plastic. Should I use one of both. I installed both with plastic over rubber. Could this be the source of my problem??<br /><br />Thanks<br />Patrick

 

[jim dozier]

Re: Rebuilt carbs wont go fast merc 45 1987

Your fuel pump isn't working properly, and your idle mixture is too lean. Now you have to find out why.

 

[SeaHorse]

Re: Rebuilt carbs wont go fast merc 45 1987

1a. Idle. back to idle adjust screws on the carbs out (CCW) another 1/2 turn.<br />1b. Float level. Don't run the motor with this lean (only 3000 rpm at full throttle) condition! Manual sets height by bottom of float, problem is, different types of floats have different bottom shapes. Turn carbs with floats up. When properly adjusted, you should be able to push float down only about 3/32 to 1/8 inch. <br />To test: assemble carbs. Use turkey baster or big syringe (best) to force gas into the carb in normal position. Gas should flow right in and when full, should not leak even when pressure applied to gas coming in.

 

[pdehardon]

Re: Rebuilt carbs wont go fast merc 45 1987

SeaHorse --- I have no idle adjust screw just mixture adjust. When I remove the cover to the Idle adjust screw there is nothing under it. Befor rebuild the motor would idle fine at 1000rpms but not slower.

 

[jim dozier]

Re: Rebuilt carbs wont go fast merc 45 1987

Reread your Merc service manual. If you don't understand something ask for specific clarifications here. If you still find the manual of no use, purchase a Clymer or Seloc manual instead. I don't know if your engine has an idle mixture adjustment screw or not. Your idle is too lean. Find the idle mixture screw and enrichen it if there is one. If there isn't one (meaning you have a fixed idle mixture jet) then either there is still some crud in there or you have an air leak or both. You are also describing a failing or non-performing fuel pump. Reread your Merc manual on the proper location of the fuel pump diaphragms, since you have been into it and it isn't working right (you said pumping the bulb helped) I suspect something you did in there was incorrect.

 

[pdehardon]

Re: Rebuilt carbs wont go fast merc 45 1987

Jimd -- The Merc maunal shows only one diaphragm in each carb. My rebuild kit had 2 in each kit. One of rubber one of plastic. Can you recommend which to use???

 

[jim dozier]

Re: Rebuilt carbs wont go fast merc 45 1987

No I don't own a Merc and each model is different anyway. Somebody on this board will eventually chime in that knows. I'm basing my comment that you have pump problems on the fact that pumping the bulb improved things. If nobody here knows which diaphragm to use you could probably call the shop where you got the parts. I do know that sometimes rebuild kits for carbs and pumps, etc. contain parts for multiple engines and it may be that you only need one of the two that came in the kit. I would use the one that looked like the one that came out unless somebody says differently.