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Tohatsu 9.8 rev limiter?

Stcroixsail

New member
Hey All,

Recently purchased a 2009 tohatsu 9.8 four stroke. Ran great for about a month. Then it would die at about half throttle or less. I replaced everything fuel related from the tank to the cylinder including filters, pump, primer, carb plus spark plugs. That fixed it for 6 hours then it would run great and idle and slightly above but anything more and it would totally bog down and shake. I took it to a outboard mechanic in a boat yard and he said it was the rev limiter putting it into safe mode and preventing it from reving up. From a cold start it runs fine but after about a minute it bogs anything above idle. He cut the rev limiter wire and charged me 244$. Put it back on boat and instantly had the same problem. Now sometimes it dies even in idle. Took it back to mechanic and he said it was the switch that gets triggered when in gear telling the motor it’s ok to rev high. Tells me to replace the switch myself, doesn’t work. Told mechanic and he said have you tried googling the problem. top notch mechanic ......... I have a great short video of the problem in action but the file type won’t upload here. If you’re interested or think you can solve it and want to see the video please pm me here and send an email or phone number and I’ll send it right away. Any help would be extremely appreciated. Or just text or email me. 8087251072 [email protected].
 
OK, so from the beginning.

First, when referring to Tohatsu/Nissan outboards for servicing, always use the model. Year is irrelevant. You likely have an MFS9.8A3. I have one myself on my sailboat. It sounds like you took a shotgun approach to the fuel system, which should work (if you have a fuel system problem), but is quite expensive. Better to diagnose. Then repair.

Your original problem *may* have been due to fuel starvation; possibly a dirty carb. But it could just as well be a result of overfilled oil. Always check on the dipstick. 1/2 to 3/4 is good. Run non-synthetic 10w-30, preferably type FC-W.

Your mechanic is an idiot. The high speed ESG (rev limiter) is internal to the CD. There isn't any external wire to cut to disable it. The motor should be able to rev over 6000, but never above about 6250. At that point the ESG will stagger the ignition to keep the motor from destroying itself. So he completely ripped you off for that $244.

Since he didn't fix it either time, he apparently decided on telling you some kind of voodoo about the neutral safety switch. That switch merely prevents the starter solenoid from engaging if you are not in neutral. It has absolutely nothing to do with revving. The motor would work just fine even if you threw that switch away; It is merely there to prevent the electric starter from engaging unless you are in neutral. You didn't mention whether you have electric start; If not, you do not even have a neutral switch.

Now then for carb basics. Today's fuel is dirty and will varnish modern, EPA-rated carbs if left in there to sit and evaporate. You must either run the carb dry at the end of the day, or drain it with the drain screw, unless you will be running the next morning. It usually takes about a week for the varnish to start forming, and from that point forward, the low-speed circuits will be too lean.

I would be happy to help. You can PM me or email directly: [email protected].
 
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