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I know I'm not the only frustrated owner of one of these but here is the feedback from a phone call this afternoon to Yamaha Outboard Customer Relations. I've rebuilt these things 3 times on my 2003 f40tlrb which came on my "new" 1983 13 foot whaler last summer and the motor still runs like crap in the low end. I also bought a Morgan CarbTune Pro this spring to synch the carbs (in addition to buying all new jets last year). Even though I synched it according to the shop manuals instructions, I did it wrong, as you will see, even though the engine idle improved dramatically.
These steps are in addition to what you would normally do when rebuilding the carbs..
The float bowl has an inacessible check valve in it..when you shake the bowl, you should hear it rattle. If it doesn't, soak the bowl in either warm Dawn dishwashing soap or simple green to clean it (it could take several days). An ultrasound jewelry cleaning machine is also highly recommended (if you don't have access to anything else). All aluminum carb parts and passages are coated with varnish to protect them. If you use aerosol carb cleaners, you will remove the protective varnish and potentially ruin the carbs.
To synch the carbs, you need to use the idle air adjustment screws, not the throttle screws. Synch the throttles with the throttle adjustment screws so they are all fully closed and wide open evenly. Drill out the brass covers (gently so you don't go into the screws) to accept a #6 sheet metal screw, which you will then use to rock the covers out. The only reason given for the covers is to keep people away from the idle screws. While it is recommended that you replace them with new ones afterwards, a little caulk in the holes is fine since they have no function other than to keep people away (like the proverbial guard dog in the computer room). Initial air screw adjustment is 2 +/- 1/2 turn. Now hook up your synchronizer and synch using the idle air screws and replace the caps.
Its also recommended that you run the carbs dry daily. There is a plunger on the fuel hose intake connection on the cowl..when pushed down and held, this lets air into the fuel so it will all burn up. If you don't, you wont burn all of the fuel up. This is not in the owners manual.
Lastly, in the 2009 marine technical guide, which is only available to dealers, on page 2-11 there are carb rebuild steps itemized. There is also a modification procedure listed (with an available video) for drilling out a bearing in the housing to get access to the accelerator pump nozzle/jet for cleaning. They couldn't provide me with a copy for liability reasons (aka fires, etc.) but if anyone out here has access to it, I would love to get a copy. According to the rep, it is a highly effective modification.
I'll let you know how it works out..its supposed to rain all next week so I'll probably dig into it then..
Cheers
MikeL
These steps are in addition to what you would normally do when rebuilding the carbs..
The float bowl has an inacessible check valve in it..when you shake the bowl, you should hear it rattle. If it doesn't, soak the bowl in either warm Dawn dishwashing soap or simple green to clean it (it could take several days). An ultrasound jewelry cleaning machine is also highly recommended (if you don't have access to anything else). All aluminum carb parts and passages are coated with varnish to protect them. If you use aerosol carb cleaners, you will remove the protective varnish and potentially ruin the carbs.
To synch the carbs, you need to use the idle air adjustment screws, not the throttle screws. Synch the throttles with the throttle adjustment screws so they are all fully closed and wide open evenly. Drill out the brass covers (gently so you don't go into the screws) to accept a #6 sheet metal screw, which you will then use to rock the covers out. The only reason given for the covers is to keep people away from the idle screws. While it is recommended that you replace them with new ones afterwards, a little caulk in the holes is fine since they have no function other than to keep people away (like the proverbial guard dog in the computer room). Initial air screw adjustment is 2 +/- 1/2 turn. Now hook up your synchronizer and synch using the idle air screws and replace the caps.
Its also recommended that you run the carbs dry daily. There is a plunger on the fuel hose intake connection on the cowl..when pushed down and held, this lets air into the fuel so it will all burn up. If you don't, you wont burn all of the fuel up. This is not in the owners manual.
Lastly, in the 2009 marine technical guide, which is only available to dealers, on page 2-11 there are carb rebuild steps itemized. There is also a modification procedure listed (with an available video) for drilling out a bearing in the housing to get access to the accelerator pump nozzle/jet for cleaning. They couldn't provide me with a copy for liability reasons (aka fires, etc.) but if anyone out here has access to it, I would love to get a copy. According to the rep, it is a highly effective modification.
I'll let you know how it works out..its supposed to rain all next week so I'll probably dig into it then..
Cheers
MikeL
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