Carburretor help please

[GAVMAC321]

Hello all, i have a Yamaha 40VEO 2 stroke outboard. Usually runs very well. Yesterday however at low rpm it started bogging down and was a little troublesome to get running. Once running it was bogging at low rpm then off like a scalded cat. I'm sure it's the pilot fuel circuit at fault with crud.

Can anyone help me with an exploded diagram of the carbs and some info for setting the floats heights and setting the pilot screws how many turns please ?

Cheers 👍

[beamishken]

Originally Posted by GAVMAC321

Hello all, i have a Yamaha 40VEO 2 stroke outboard. Usually runs very well. Yesterday however at low rpm it started bogging down and was a little troublesome to get running. Once running it was bogging at low rpm then off like a scalded cat. I'm sure it's the pilot fuel circuit at fault with crud.



Can anyone help me with an exploded diagram of the carbs and some info for setting the floats heights and setting the pilot screws how many turns please ?



Cheers [emoji106]

Carbs are pretty self explanatory once you strip them, 2 jets to remove then a good clean & blow out often just a piece of crud in one of the jets, Unlikely you'll need to mess with the float heights. 2 potential issues I've had cause similar issues are a failed fuel pump diaphragm & another was a trigger coil, on that engine there are 2 trigger coils 1 runs 1 cylinder the other runs the other 2 mine was dropping the 1 cylinder when slowing the revs, it was like it was switching a cylinder off at lower rpm changed out the trigger coil & cured it.

[User name]

Clean out the jets first before making any other adjustments. 90% of the time this will be the cause of your bogging down. This diagram might help.

[paintman]

Before doing anything else with pilot or other adjustable screws do them up fully counting the number of turns/partial turns & make a note.
That way you know & can set them back to their original positions.

[paintman]

Originally Posted by beamishken

Carbs are pretty self explanatory once you strip them, 2 jets to remove then a good clean & blow out often just a piece of crud in one of the jets, Unlikely you'll need to mess with the float heights. 2 potential issues I've had cause similar issues are a failed fuel pump diaphragm & another was a trigger coil, on that engine there are 2 trigger coils 1 runs 1 cylinder the other runs the other 2 mine was dropping the 1 cylinder when slowing the revs, it was like it was switching a cylinder off at lower rpm changed out the trigger coil & cured it.

Trigger assembly on my Mercury V6 2-stroke was my issue.
3 pairs of wires on that one. One broken wire inside the sheathing so not visible. Ends so close together that a gentle wiggle would remake the break.
Engine wouldn't idle but an increase in rpm & it would. I suspect as the engine rpm increased the current was able to jump the gap.
New trigger assembly fitted.