rebuilding / cleaning a 2004 tohatsu 18hp 4 stroke carb ?

[danstead]

Trying to remove carb, seloc Manual for 18 HP has you removing carb from intake man. But 10 mm bolt behind air intake is not accessable. Would you remove carb and intake manifold as an assembly or remove the starter rope cover to gain access to 10 mm carb bolt?? So far not to impressed by Seloc manual, claims step by step detailed procedures, time will tell.
Thanks in advance!

 

[pvanv]

Re: rebuilding / cleaning a 2004 tohatsu 18hp 4 stroke carb ?

!. Scrap the aftermarket manual. It's decent tinder for starting your wood stove, or maybe as a doorstop.
1a. Get the Factory service manual from any dealer... several forum members can help you get it... even me.

2. Pull the intake with the carb attached. BTW... the carb bolts are 6mm, with 10mm heads.

3. Do a complete carb disassembly, including all jets and emulsion tube nozzle. Soak all non-rubber bits in real carb dip for 4 hours at room temperature. Blow out all passages with a liberal dose of generic carb spray -- use a whole can. Reassemble with a new kit, paying particular attention to float height.

4. Reinstall the carb to the intake, and reattach as an assembly. Use correct torque on the intake bolts. Adjust the throttle rod correctly.

5. Enjoy.

 

[danstead]

Re: rebuilding / cleaning a 2004 tohatsu 18hp 4 stroke carb ?

Thanks Paul!,
I see many diff opinions on carb dip, what do you recommend?

 

[pvanv]

Re: rebuilding / cleaning a 2004 tohatsu 18hp 4 stroke carb ?

We like the stuff that we get at the auto parts house in 1-gal cans. Typically looks like a paint can, and usually has a basket for parts right in it. There are several brands; all work OK, though none are as aggressive as the stuff we got 30 years ago.

 

[danstead]

Re: rebuilding / cleaning a 2004 tohatsu 18hp 4 stroke carb ?

Thanks again!

 

[danstead]

Re: rebuilding / cleaning a 2004 tohatsu 18hp 4 stroke carb ?

Hello Capt. Paul,

I have carb disassembled and almost ready to soak in Carb cleaner, can you please look at attached images and let me know if parts marked with red arrows (on images) need removed?

Thanks and I did purchase the tohatsu service manual from iboats for outboards.

 

[pvanv]

Re: rebuilding / cleaning a 2004 tohatsu 18hp 4 stroke carb ?

That Seloc manual is scrap paper. Too general. Get a real Factory service manual, 003-21041-0, SERVICE MANUAL MFS9.9/15/18A&B, $40.00, available from any Tohatsu/Nissan dealer, but unfortunately not available from iBoats at this time.

You should be OK with that level of disassembly of the bowl. Just make sure that the check balls for the accelerator pump plunger are working freely.

There is a rubber boot covering the link rod that actuates the accelerator pump plunger. That boot may get damaged by carb dip. Carefully disassemble the linkage that retains that "push rod" to get the boot off. Pay close attention to how the levers and spring fit -- not especially well-drawn in any manual. There should be a new boot in the carb kit.

 

[danstead]

Re: rebuilding / cleaning a 2004 tohatsu 18hp 4 stroke carb ?

That Seloc manual is scrap paper. Too general. Get a real Factory service manual, 003-21041-0, SERVICE MANUAL MFS9.9/15/18A&B, $40.00, available from any Tohatsu/Nissan dealer, but unfortunately not available from iBoats at this time.

You should be OK with that level of disassembly of the bowl. Just make sure that the check balls for the accelerator pump plunger are working freely.

There is a rubber boot covering the link rod that actuates the accelerator pump plunger. That boot may get damaged by carb dip. Carefully disassemble the linkage that retains that "push rod" to get the boot off. Pay close attention to how the levers and spring fit -- not especially well-drawn in any manual. The should be a new boot in the carb kit.

Thanks Capt. Paul,

I took a lot of pics during dis-assembly of the plunger assy with boot and springs. Can I purchase the 003-21041-0, from you?
I also removed the entire shaft assembly holding the brass ~1.0" disk held on by 2 screws inside the carb..

The intake manifold gasket stayed attached to the motor and looks brand new, should I purchase / replace that gasket?

You are a great asset and thanks for you patience and willingness to help fellow boaters / fishermen!!!

Dan from Pa.

 

[pvanv]

Re: rebuilding / cleaning a 2004 tohatsu 18hp 4 stroke carb ?

We have them. Dropped you a PM so as not to solicit in the boards.

No need to pull the throttle shaft, but as long as you are careful at reassembly, no problem. I would definitely use some lock-tite on the tiny screws that hold the butterfly on the shaft when reassembling. FWIW, you will need to reassemble the throttle plate lightly, then back off the idle stop screw so the plate can close completely, and confirm that the plate is 100% centered in the bore, THEN snug down the screws. If that plate is off even a few thousandths, idle mixtures can be "weird", and the throttle may "drag" when returning to idle.

If the intake gasket is perfect, no problem. Be sure to torque the intake bolts evenly and to the proper value.

Glad it's working out for you so far.

 

[danstead]

Re: rebuilding / cleaning a 2004 tohatsu 18hp 4 stroke carb ?

After rebuilding carb engine starts easily and runs great at higher rpms but still doesn't consistently idle well at lowest throttle setting. At first startup seems to idle OK but after running down the lake at higher rpms then slowing down Engine doesn't want to idle. If I drift fish a while And restart engine It then seems to idle better at lowest throttle setting. Could I need to open and readjust plastic float tab? Maybe not the carb?
Thanks,
Dan

 

[pvanv]

Re: rebuilding / cleaning a 2004 tohatsu 18hp 4 stroke carb ?

Odds are that you are still a little lean near idle. The ABS solenoid makes the mixture richer when the motor is warming up (leaner when hot).

First: Verify idle RPM when warm, using a good shop tach, and verify that you have good plugs.

If all that checks out, you may still have some varnishing in the idle circuit of the carb. If it's really minor, extensive running may help dissolve it, but I suspect that you will need to pull the carb again, and run through cleaning it one more time.

There is also a remote possibility that the ignition system is weakening when warm... but that typically shows up at higher speeds, not idle. To test which problem you are experiencing, you can get the motor hot enough that it won't idle correctly, and then make 2 separate tests:
1- Use your fingers to restrict the airflow at the carb silencer... that richens the mix... if the idle improves, odds are you need more carb cleaning.
2- When hot, stop the motor and quickly run the resistance tests in the service manual. If the ignition tests correct when cold, but is out of spec when hot, you need to fix the ignition system.

 

[danstead]

Re: rebuilding / cleaning a 2004 tohatsu 18hp 4 stroke carb ?

Paul,
Wow, lots to try! Thanks for your input, will try plugs and tach. Then covering intake and ohm test. Hope I don,t have to pull / clean carb again.
But it does seem to idle much better cold than when hot!
Dan

 

[pvanv]

Re: rebuilding / cleaning a 2004 tohatsu 18hp 4 stroke carb ?

Paul,
Wow, lots to try! Thanks for your input, will try plugs and tach. Then covering intake and ohm test. Hope I don,t have to pull / clean carb again.
But it does seem to idle much better cold than when hot!
Dan

Yep, that symptom of running better cold (rich) than hot (lean) is an indicator that you may still need to revisit carb cleaning...