carb removal how-to 402 merc

[corcan1]

Hello everyone

i'm helping a friend with there outboard. they bougth this motor a few years ago but have never used it yet so it has been sitting for a few years.

i checked the compression which is 120 in both cyl and it has nice blue spark. i put a little fuel in both cyl's and it started right up and burnt out the fuel then died like normal. i put fresh gas in the tank and connected the line to the engine, squeezed the primer ball and tried to start the engine... nothing. not even an offer so i'm pretty sure the carb needs cleaning.

i started to removal the carb but i'm having a hard time with the nut on the starter side.... it's behind the fuel inlet elbow.... whats the best way to remove this nut?

i've included a pic of the said nut.

also, i believe the motor is a 1977 or 78
here is the serial
7102156
it's got the word Rocket stamped on the cyl above the serial
numbers 402 on the leg and it's a 2cyl 40hp merc.

hope someone can tell me how to get this nut off! lol!

 

[catcatcher]

Re: carb removal how-to 402 merc

The way I did it on my 650 which had the same problem is take the bowl cap off which gets the line completely out of the way. I was rebuilding the carbs and the gasket comes with the rebuild kit to mount the cap back to the bowl. Hope this helps!

 

[corcan1]

Re: carb removal how-to 402 merc

thanks for the reply. ya, i studied it a little more and also decided that was the only way to get the carb off.

i was hoping to just clean the carb but looks like i might have to get a complete kit now that i took off the inlet piece and the gasket tore a bit during removal.

as soon as i took that piece off i could smell the old fuel.

will update on my progress as i go along.

 

[corcan1]

Re: carb removal how-to 402 merc

well, decided to put the carb back together and give her a try. squeezed the ball till it was hard and checked for leaks, none. so cranked her over a bit with the choke. got nothing but could see a bit of gas dripping from the front of the carb. put a little fuel in the plugs and it started right up.. it idled ok, but after 20 seconds it stalled. started it again but this time i need to use the choke every few seconds to keep it running. guess there is still some gunk in the jets, low speed one anyways.

now, the only outboard carb i ever worked on is on my 65 33hp evinrude which is pretty different from this merc. could anywone tell me where the low speed jet is? maybe a diagram would be best?

thanks everyone!

 

[daveswaves]

Re: carb removal how-to 402 merc

The low speed jet is behind the low speed adjust needle, which is on the right hand side front of the carb. It is the only adjustment needle on that carb. The high speed jet is behind the brass hex plug on the front of the carb. If you could smell the old fuel then you are correct, that carb has to be cleaned. There is also a screen filter behind the fuel elbow on the fuel bowl top that you removed. It should be discarded as per a merc service bulletin, they had problems with them restricting fuel. Very simple carb. If you are going to remove the brass slotted plugs make sure you have the right size screwdriver, they are brittle and will simply chip with a screwdriver that is too small. Soak the carb in carb cleaner and blow out the passages with compressed air. Do not run a wire through the passageways. Get it cleaned up and it should run like a champ.

 

[corcan1]

Re: carb removal how-to 402 merc

update:

screen filter was already removed i guess by previous owner as i did not see any screen.
instead of taking the carb back off i just backed out the low speed screw and sprayed some carb cleaner in the passage way then a few shots of compressed air. reasembled and started the motor in a barrel. adjusted the lowspeed screw and it idled well. thanks for the info.

now other issues i have found:
decided to bring the boat to the lake. this is the first time i've had this boat in the water. no leaks so i guess thats a good thing! hehe! boat started fine and first thing i noticed is no reverse gear, only a rapid clicking....... slowed the motor all the way down but still would not go into reverse. decided to try forward gear since i was already on the lake, it works fine, no strange noises so we shoved off from the dock and started to head out... problem #2: last person that owned the boat wrapped the cables backwards on the spool!!! steering is backwards! this i can fix myself, but damn... why would someone leave a boat in this condition?! anyways.... last problem #3: motor won't rev... no speed ... guessing i should have removed the carb and cleaned the high speed jet / passage too either that or its just running on 1 plug... will check for fire this weekend.

so, any idea what the reverse gear problem could be?
is there an adjustment for the cable?
with the engine off i put it into reverse with the control box but the prop spins freely one way and a slight ticking noise the other. when in forward gear it works as it should.