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Tohatsu 9.8A3 4-Stroke woes....

wgdenge

New member
Hello All,

I have an older (not sure year) 9.8 that is giving me fits. It was on a sailboat i purchased and ran great for the 1st 2 years. Then last year, it started to lose power and almost die when motoring. (Fuel starvation?)

So, I removed the carb, and after removing all parts soaked for a bit, then put into a ultrasonic cleaner to get last bits of gunk. I purchased a rebuild kit, but it was nothing more than a few gaskets, float and float-needle.

I put all back together, and tried motor. Seems it did not help much. Idles GREAT, but as soon as I put into gear, it almost dies. When throttling up, it has almost no power.

What might it be, float height? The float seems to be non-adjustable. Spark? Idle is great.. Fuel pump?

Anyone who can help, please let me know what to do next.


Thanks for listening.

Wayne
 
Assuming your model is MFS9.8A3. Year is irrelevant for servicing a Tohatsu outboard.

One thing often overlooked is oil and oil level. Change the LU and crankcase oils every 50 hours or annually if you don't put a lot of hours on it. Run non-synthetic 10w-30 type FC-W oil, and keep it at about 3/4 on the dipstick. Never even a drop over full.
Another thing is to run E0 non-ethanol fuel only, 30 days old or fresher, and if not running for a few days, always run the carb out at the end of the day. If you forget, you can open the drain screw and drain it that way.

Your symptoms still indicate a carb problem. Remember that there are two carb base gaskets, one on each side of the thermal spacer at the intake. The float is technically non-adjustable. If you invert the carb, and the float sits parallel to the casting, the float height is good. Remember that there is a rubber plug that closes off the bore for the secondary jet; the fuel must first pass through the main jet before feeding the secondary. If that plug is missing, mixtures will be way off. Set your idle speed about 950-1000 in neutral. Check plugs. It sounds odd, but I have gotten bad plugs out of the box. Color will tell you a lot. If you have tinkered with the pilot screw, and richened the idle, that could be covering up a too-lean condition, but might give you a decent idle.

When we clean carbs, we do an overnight soak (at least 4 hours) in the 1-gallon-can-type of cleaner, then an hour in the same fluid in the ultrasonic at low heat (under 130F), and finally, use a whole can of spray-type carb cleaner to clear all passages. Depending on the varnishing, we may need to repeat that process. Thanks to the US EPA, the cleaners we get today are pretty wimpy. I wish I could get about 5 gallons of the old TYME cleaner. Sigh.

On the 9.8, the fuel pump is pretty robust; When those pumps fail, they usually blow the diaphragm, and dump fuel into the crankcase. Also, a failing pump would typically cause you to "run out of gas" as you run at high speeds... but typically does not affect low speeds, or "tip-in" as you transition from idle to speed. If you suspect a pump issue, you can squeeze the primer; if the power comes back, your hand pumping fixed the problem (temporarily), and you know you have a fuel delivery issue, such as a bad o-ring in a connector, or a clogged vent.

I would break down the carb and clean it again, and carefully reassemble it, making sure everything is correct.
 
Sir,
Thank you for the fast response. I will pull the carb this evening and soak in DIP overnight.
I read in other posts of yours about the 'rubber-plug' I have had that card apart, jets, ect. and have never seen a rubber plug. I cannot see it on the parts diagram. Where does it go? Can you provide a PIC or something? That sounds like it is my issue. (Bad Mix).

Again, thank you for help.

Wayne
 
It's item 1-2 in the picture. I assume you did pull the jets while cleaning, right?
3V2031690MPLUG$5.38
 
There are two wells for jets. One takes the main jet, the other the low-speed jet. The low speed jet is covered by a plug, usually rubber.
 
Hey Paul,
Want to thank you for your help. It's folks like you that keep guys like me from going postal.
Anyway, here are a few pics. Mine seems to have a brass screw-plug.
I have it all sitting in Chem-Dip overnight.
IMG_2072.jpg
IMG_2081.jpg
IMG_2083.jpg
IMG_2084.jpg

V/r
Wayne
 
Yep. Yours looks fine, with the brass plug. The jets and emulsion tube "nozzle" look like a lot of water has been in the fuel, possibly dissolved in E10 gas. Hopefully after a thorough cleaning, you will be OK. After the soak, and a round in the ultrasound, blast out each and every passage (including those small holes in the nozzle) with a whole can of spray carb cleaner.
 
So, I put carb in dip along with jets overnight. I cleaned them with carb spray and went thru holes in jets with very fine wire. I blew cleaner thru all ports in carb housing. Everything was clean as a whistle. Hard to tell about the non-adjustable needle?????
I re-installed this evening, and it started right up. Idles great. But symptoms still exist. Slipping into gear it almost dies. Giving it throttle is is VERY weak.

I have new plugs coming as well as new gas line just to make sure.


I'm just about ready to get new carb. All the trips back/forth, cleaning, parts, ect.. Would of paid for a new carb already.

So, where do I get a 3V2PB-5DI carb.??

Cheers,
Wayne

IMG_2072.jpgIMG_1475.jpg
 
Never ever push any kind of wire anywhere in a carb. It causes scratches, which causes weird mixtures at some velocities. Assuming the carb is the issue, new ones are available. I'm a dealer. There are two different carbs; I assume you have a tiller-operated motor. You are referring to the casting number, which is not the part number.
For tiller models:
3V2031003MCARBURETOR, F9.8A2/A3 (F)$188.65

For Remote models (uses electric choke):
3V2031333MCARBURETOR, F9.8A2/A3 (P)$222.05

I can ship in two days after I receive your payment.
 
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