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Tohatsu 9.8, 4 stroke, 30 hours+, 1 yr.

M

Munozafa

New member
Wow! lots of good info here! I leafed through past posts and found out about everything I need to do...and confirmed everything I've done thus far. I do run the gas out every time but with idle and running problems after sitting 2 months, this is what I've done so far...replaced fuel filter, replaced plugs, took out carb and soaked it 10 hours, cleaned gas can and fuel line, got new fuel with STA-BIL added, and changed oil. whew! I see that I need to drain a little oil out to bring it to optimum level, soak my parts again and hit it with compresses air when I remove it, add a little techron injector cleaner to the gas, and I may change to a better gas stabilizer. All I'm missing is a new carb kit, but everything looks good in there. When I originally opened the carb there was a orange granular substance, which i assumed was gas varnish. I want to avoid adjusting things that I am not qualified to adjust but if this last effort does not work I will take her in to the dealer.

So, first question, what is the best gas stabilizer to use?

Second question, I bought this new one year ago. If I have to take it in, what will I have to pay? just labor, or does the warranty cover everything?

I think that's all the questions I have. Please feel free to ask about any of these steps I've taken or make suggestions as you see needed. Thanks!

Munozafa
 
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The 9.8 is a good motor all the way around -- light, quiet, powerful, economical, durable; Of the 4-strokes, it's my favorite design; It's the model I have myself. Yes, It is best to run the carb dry at the end of the day. That's to prevent varnish formation in the passages. Plugs can be changed based on a visual inspection -- they don't need replaced unless they look bad. If you run a 10-micron water-separating fuel filter (and change the cartridge annually or when it has water in it), the internal gas filter will last longer. Techron-type injector cleaner doesn't hurt, but will only address very minor varnishing. It's prudent to change the LU lube at 10 hours, then every 50 hours or annually, whichever comes first.

Oil level is critical -- not even a drop over full, or you will invite a host of problems; 1/2 to 3/4 on the dipstick is fine. If you have a lot of WOT in that 30 hours, you can be near Full, but never over; If that 30 hours has been mostly at idle/trolling, stay below Full.

The residue in your carb bowl may have been exacerbated by using too much stabilizer and/or could be a gel/crud that happens when some stabilized fuels mix with water. As long as that junk hasn't damaged the needle/seat, you probably don't need a carb kit. If in doubt, toss in a new kit when reassembling the carb after cleaning. As for the actual cleaning of these carbs... There is no substitute for completely disassembling all jets, emulsion tubes, etc., and submerging the castings in a good carb dip such as Tyme, for about 4 hours at room temperature. We usually blow out the passages with cheap carb spray after the bath. Lesser (spray) cleaners alone are not aggressive enough to dissolve the organic residues. Less dunk time is ineffective, and too much time will start to attack the factory coating on the castings, causing discoloration, and exposing the raw metal to any water in the fuel (or salt in the air), accelerating corrosion. No solvent will clear oxidation, so if there is hard, white powdery aluminum oxide in the carb, it's probably time for a new one.

If running stabilizer in the gas, we like K-100 stabilizer. The MG (marine) formulation is better than the G (automotive) grade. Regardless, we have found that it is still best to not use fuel more than 30 days old. The Tohatsu warranty covers anything that is a manufacturer's defect, but does not cover problems caused by bad fuel. If there is a flaw in the carb, that's covered, but crud in the fuel is not something that the Factory can control, so it's outside the scope of the warranty.
 
Again, good info there. Thank you.
There was a little oxidation at the bottom of my carb; i just cleaned it up, but you recommend a new carb.
Does the new carb come with a kit or do I have to order carb kit separate?
Once I get all that, can I just install it or are there technical adjustments to be made? I heard mention of a tach test and float adjustment...
Are the jets and emultion tubes those brass looking parts inside the carb, or are they somewhere else?
I do need to do the LU lube...thanks for that reminder...

Uhg!

THANKS.

Munozafa
 
Start with a factory service manual, Part # 003-21056-0 List Price (MSRP): $26.52.

Is the oxidation in the carb body, or just residue in the bowl? If the former, you may need another carb; If the latter, you may be OK. You will know after you put it back on (after a proper soak) and test/setup the motor. If you don't understand the concepts of jets and emulsion tubes, I suggest you get some more experienced help on the job. Yes, they are brass. You will also need to remove the SS cover from the top before dunking. A new carb comes complete, so no kit is needed to install it. The float is plastic, precision cast, and I have not needed to adjust height on one. To check the height, invert the carb, and the float should sit parallel to the carb casting under the force of gravity. After you have a good carb installed, you will want to warm up the motor and adjust idle speed, both in gear and in neutral. A good shop tach is the best and most accurate way to do it (specs are in the manual), but you can also do it "by ear". You want the idle high enough to prevent stalling when idling in gear, but slow enough to prevent slamming when going into gear.
 
Again, thank you! She is running well on the stand (connected to the garden hose). I still need to replace the LU lube before I put her in the water (any recommendations, or just go by the owners manual, API GL-5:SAE#80 to 90??).
I just ran it out of gas, though when I removed the drain screw more gas came out of the carb. Is that the the norm?
I'm trying to get some K-100 MG but the website wants $10 handling plus shipping. I requested a list of nearby dealers that carry it. Other boat guys highly recommend Pri-g stabilizer....
All that plus the little bit of techron and I'll be ready to make some waves! I still may order the new carb becsause it seems like the need is in my future.
MM
 
Pretty much any GL-5 90-weight lube will work fine. You don't want the Type-C stuff that was formulated for electric shift OMC units. Probably won't find that on the shelf anyway, except maybe in the Sierra squeeze tubes. There are super-exotic and semi-synthetic blends out there, and they work fine, but really aren't needed. For a detailed description of an LU lube chamge, see http://www.tohatsu.com/tech_info/oil_change.html

Yes, it's normal to get another teaspoon of gas out of the carb drain, even after running it out. That's why we drain all the carbs on motors we winterize. If you run only top quality fuel, and never let it get older than 30 days, stabilizer can be considered optional. If your local guys are having good results with a particular brand of stabilizer, there's no reason not to try it, but again, if you strictly follow the new gas rules, it shouldn't be critical.

As for the carb -- if you do in fact need one -- remember that there are 2 different carbs; The 3V2031002M CARBURETOR, F9.8A2/A3 $164.53 is for tiller (type F) motors, and the other 3V2031332M CARBURETOR, F9.8A2/A3 $193.67 has the additional linkage for the electric choke of remote (type EP) models.
 
Well Paul, since you don't seem to be charging by the answer....My local marine store manager told me that the Quicksilver brand LU lube SAE 90 was what he recommended...or should I say what he had available. I used to run this same stuff in an older 100 hp Mercury as well. I've already put it in, and thank goodness my old LU lube was only dark and not milky. Is this LU lube acceptable? Thanks again for the link to the lube change steps. I needed the refresher!
 
That lube should be fine. Don't forget that this motor is also sold as the Merc 9.9, and the Merc shops would use that lube as de rigeur.
 
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