We have a Honda 8 & a Honda 9.9. The internal throttle linkages on the
Honda outboard motors are all mechanical pushrods & bellcranks with no
cables to kink or bind. Usually a cable linkage will not kink if it is
properly supported along its length. Consider checking along the throttle
cable to see if a support clamp has vibrated loose or is simply missing.
You may find it lying in the bottom of the motor housing.
Regarding stalling when shifting - it sounds like your idle speed is set too
slow. The Honda outboard's have an idle speed adjusting screw on the
throttle linkage at the carburator. Your Yamaha outboard probably has
something similar for setting idle speed. Your owner's manual will have an
idle speed specification. From my owner's manual, the Honda 9.9's idle spec
is 1100 +/- 50 RPM with a warm engine. If you are having trouble with
stalling while shifting, then I would set the idle RPM to the upper end of
this spec.
Once the idle speed is set to spec, if the motor still wants to stall when
shifting, then I would check the following:
- Clean & set the gap on your spark plugs to spec
- Consider replacing the spark plugs if they look questionable
- Look at the spark plugs. They should look chocolate brown @ the
electrode. If black & sooty, then the air/fuel ratio is too rich & the plugs
are fouling - suspect float level too high. If gray or white, then the
air/fuel ratio is too lean & the mixture is difficult to ignite - suspect float level
too low, clogged jets, or vacuum leak
- Check to be certain you are getting a good strong spark to both plugs
You may need to replace your plug wires, coil, &/or CDI module if
there is a spark problem NOTE: I doubt it's an ignition problem - more likely a
fuel delivery problem or a vacuum leak
- Clean out the jets in the carb
- Set the float bowl fuel level to spec
- Check the connections, gaskets, & any rubber hoses in the engine intake
manifold for a vacuum leak
Still haven't found the problem? Then, I would check these last 2 items:
- Set the ignition timing to spec
- Verify that the ignition timing advance mechanism works to spec
If all this doesn't solve your stalling problem, then I would pack the
engine back to the dealer.
I'm betting a simple idle speed adjustment will solve your stalling problem.
Roger Pihlaja
S/V Dynamic Equilibrium
14 Nov 2001
During the day I thought of something else to check re your stalling
problem.
Some carburetors have an idle air/fuel ratio mixture adjusting screw. On my
Honda 9.9, the proceedure is to gently screw the idle air/fuel pilot all the
way in (clockwise) & then back it out (counterclockwise) 2-3/4 turns. This
is the basic adjustment & you may have to reset the idle speed again after
doing this. An experienced mechanic usually fine tunes the idle air/fuel
ratio by listening to the engine idling. If the engine is still stalling at
the basic 2-1/4 turns counterclockwise setting, then the problem is usually
an air/fuel ratio that is too lean. The engine manufacturers are trying
real hard to meet the emission regulations & this tends to drive them
towards setting up their carbs on the lean side. To richen up the idle
air/fuel ratio, turn the pilot screw out counterclockwise 1/4 turn & listen
to how the engine runs. Keep turning the pilot screw out 1/4 turn
counterclockwise until the engine runs smoothly & doesn't stall. I realize
that proceedure sounds a little artsy-crafty, but that's how mechanics fine
tune the idle air/fuel ratio.
In order to meet emission regulations, some manufacturers seal the idle
air/fuel ratio mixture screw with lead or epoxy so you can't adjust it. If
this is the case with your Yamaha, then you will have to take it back to the
dealer.
Roger Pihlaja
S/V Dynamic Equilibrium
14 Nov 2001
