carb draining

[docksider]

So, with a bunch of small outboard and yard machines, I'd never drained a carborator until this year, when I followed the clear instructions on a Yamaha generator for how it's done. I've always used Stabl and run the motor dry.

Now that I've drained a carb and seeing where the manuals suggest it, I'm happy to try with my OB and other motors, including a tohatsu 9.8 2008 4 stroke, if only I can be sure I know what I'm doing.

So, with nothing in the manual of 9.8 to go by, I still think I know what/where the carb is. I see a brass looking screw/bolt that is pretty "low" on what I think is the carb. Is this the drain port????. On myYamaha generator the drain was a brass needle valve with a spring around the threads.

Sooo, on a Tohatsu 9.8 where is the carb and what does the carb and it's drain **** look like?

OR, since I've not had a problem with this or any other motor, should I even care? (Other motors = 1955 5.5 Johnson, 1971 9.5 evinrude; 1981 35 hp johnson; 1998 15 hp yamaha; 2008 9.8 tohatsu; and many other lawn mowers, tractors, trimmers, chainsaws, etc. )

Thanks in advance.
d

I'm conscientious, but not really knowledgeable. Hence I ask.

 

[pvanv]

Re: carb draining

Depending on the climate and the length of the winter layup, the 4-strokes should be fogged, and have the fuel system drained for best results.

There are 2 big differences in what happens with modern 4-stroke OB's today, versus what used to happen with the 50-1 premix 2-strokes of years ago. As a result, we see a lot more fuel-related issues than we ever did in the past.

First, since the modern E-10 fuels spoil rapidly, especially when exposed to atmospheric conditions, it's best to get rid of it, instead of keeping it in the fuel systems over the winter. This is not really a forum to discuss gas chemistry, but suffice to say that if the gas isn't stored in the system over the winter, it's not going to be an issue in the spring.

Second, most of these EPA 3-star (and higher) rated motors run very very lean. The Tohatsu/Nissan 8/9.8 is no exception. In order to keep good fuel atomization at those lean ratios, the engineers design fuel systems with very small passages. That translates to very high air/fuel mixture velocities, maintaining good fuel atomization. That also means that even very minor varnishing can cause major carb problems.

In addition, since the 4-strokes don't have premixed oil running through them, they are more prone to rusting of internal surfaces, such as valve faces and cylinder bores, especially if stored outside, or in a damp area. Fogging reduces that.

In our shop, we do winter storage for any of our customers who don't want to do it themselves. This includes fall layup -- which includes engine fogging, and draining of all fluids (motor oil, gear lube, and yes, fuel). In the spring, the motors get fresh LU lube, fresh motor oil, fresh fuel, and a tank test. We've been doing this for a few years now, and have 100% customer satisfaction on these motors.

Based on this experience, I would drain the fuel system on your 9.8 if your winter layup is going to be several months. The carb drain screw is on the starboard side of the carb, near the bottom, and accepts an 8mm wrench.

 

[docksider]

Re: carb draining

Thanks, Paul, for the thorough reply. I'll look for that 8mm bolt in the morning light and give it a try.

BTW, all the other winterizing steps you describe HAVE been part of my winterizing routine, and I have used Stabl faithfully.

Come to think about it, however, I couldn't discern where to fog this Tohatsu. It's always been pretty obvious on other motors. Last year on this 9.8, I didn't fog, I did squirt some fogging oil in when I changed the plugs, but that's not the same.

Thanks again.
d

 

[pvanv]

Re: carb draining

If you use the foaming type of fogging oil, squirting it into the plug holes is a pretty good treatment. As it foams up and expands, it should make it past any open valves. Of course, if that cylinder is at TDC, both valves are closed.

The 9.8 air silencer does not have a "fogging port". We usually blow the fogging oil through the intake screen, or I suppose you could detach the breather hose (comes from the top of the intake manifold) and squirt fogging oil into the air box through that opening.

Keep in mind that the 9.8 intake silencer has a reservoir or "puddle" cast in the bottom (to collect any motor oil that makes it through the breather hose), so you definitely want to fog while running -- otherwise, you'll probably just fill up the reservoir, rather than getting the oil to the valves.

 

[docksider]

Re: carb draining

Thanks, Paul.
While draining the carb this morning I did notice that screen and figured that's where the air goes in. I'm out of the water for the season, and everything else for this motor is complete, so I'll skip the air intake fogging this year and give it a try next.

I see you're in the buffalo area. I'm in central NY, but get to western NY now and then. If i get a chance, I'll come see your place. I like to visit marinas.