slow in-gear speed on a 9.8HP TOHATSU

daveznspace

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I have a 2007 9.8HP TOHATSU MODEL# MFS9.8A3EFS that's not getting full power when in gear.

I use it frequently (usually at least once a week), however this issue started after I hadn't run it for 2 weeks which of course is a short amount of time. At the time I did'nt know you are supposed to run fuel out after every use so there was fuel in there and during that time there were some big storms and this boat is on a dock uncovered. I do always add sta-bil to the fuel.

Basically when you start moving and go to hit full throttle it just barely gets going, I can get it up to about 20mph usually but right now maybe it gets 4-5mph.

The carb was rebuilt a yr ago.. it didn't need it except the previous owner tried to clean it and couldnt get it back together so I took it in and had it done.

Here's what I have done so far:

Checked compression: both sides around 130 (128 & 130)
New plugs
New fuel tank
new fuel lines (tank to motor)
cleaned out fuel filter
Did a Seafoam cleaning (3/4 gallon gas to one 16 oz bottle of seafoam.. run for 15 min, sit 15, run 15 sit 15)

I tried to adjust throttle bar but that hasn't gone well either. If I set it so it doesn't rev up when started and is around
a good idle speed then the throttle won't go all the way up.

Does it sound like a carb rebuild or maybe the low jets need cleaned?
 

TOHATSU GURU

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Re: slow in-gear speed on a 9.8HP TOHATSU

El cleano the carbo. It's unlikely that you would need to rebuild the carb. It's just old dried up fuel residue that is clogging everything up. The carb needs to come off, apart, soak in cleaner for hours and then be put back together.
 

daveznspace

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Re: slow in-gear speed on a 9.8HP TOHATSU

Thanks, that's what I was figuring but just making sure before I do this. Is it necessary to get a rebuild kit to just clean it like this?
Thanks for your time
 

pvanv

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Re: slow in-gear speed on a 9.8HP TOHATSU

A kit is not needed very often, unless the bowl o-ring was damaged, or the needle valve viton is distorted. All parts need to be disassembled (including both jets, and the emulsion tube "nozzle"), then a 4-hour soak in real carb dip (available at auto parts houses in 1-gal cans), followed by a good rinse-off, careful reassembly (checking float height along the way), and you should run a lot better. To adjust the throttle rod, set the tiller to idle, make sure the choke is off, and install the rod with a little slack (about 1/2 mm) at the pin where it actuates, then snug down the phillips-drive screw. If you remove all the slack, you may not be able to set the idle stop screw down where you want it, and if there is too much slack, you won't be able get full WOT.
 

daveznspace

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Re: slow in-gear speed on a 9.8HP TOHATSU

Thanks, that answers my other big ?
I tried to find a service manual today but couldnt find one so I'll order one tonight and give it a try.

thanks again
 

pvanv

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Re: slow in-gear speed on a 9.8HP TOHATSU

For the Factory service manual, get Part # 003-21056-1 $27.58 from any Nissan/Tohatsu dealer, including me. It is specific to the 9.8A3. Don't bother with the aftermarket "wood stove tinder" manuals.
 

daveznspace

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Re: slow in-gear speed on a 9.8HP TOHATSU

How do I get one from you


For the Factory service manual, get Part # 003-21056-1 $27.58 from any Nissan/Tohatsu dealer, including me. It is specific to the 9.8A3. Don't bother with the aftermarket "wood stove tinder" manuals.
 

daveznspace

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Re: slow in-gear speed on a 9.8HP TOHATSU

took carb off and disassembled and soaked all metal parts in berrymans dip for 5 hrs then sprayed out with berrymans carb cleaner spray and let dry... reassembled and put back on boat.... doesnt run any better lol
 

TOHATSU GURU

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Re: slow in-gear speed on a 9.8HP TOHATSU

And you still have not cleaned the carb, although I bet it is real shiny...No spray cleaner is strong enough to dissolve the clogged up passages and jets. You need to get a one gallon pail of carb cleaner and clean the carb.
 

daveznspace

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Re: slow in-gear speed on a 9.8HP TOHATSU

I did soak it in a pail of carb cleaner for 5 hrs... used berrymans chem-drip carb & parts cleaner... then sprayed out with the can because I have seen that recommended over blowing air thru it.
 

daveznspace

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Re: slow in-gear speed on a 9.8HP TOHATSU

should I maybe take it back off and do an overnight soak?
 

TOHATSU GURU

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Re: slow in-gear speed on a 9.8HP TOHATSU

Yep...Either the dip did not have time to eat the varnish out or....You have another problem. Chances are it is still the carb at this point. Sometimes we end up cleaning them twice before we get success. Sometimes you have to just give up and replace the carb, but that is rare. If the blockage is a metal spur the cleaner will not do anything and you just have to write the carb off. Unfortunately most diagnose is by elimination of each possibility rather than a "one test tells you what to fix'.
 

daveznspace

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Re: slow in-gear speed on a 9.8HP TOHATSU

Ok its back apart and in the soak... i will let it soak at least overnight this time.
I did realize that right before this happened I bought gas from a new station thats "in the ghetto" lol but I'm guessing the gas there is less than stellar.
 

TOHATSU GURU

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Re: slow in-gear speed on a 9.8HP TOHATSU

Depends:)...The main thing is to prevent the varnish from forming and to to that the carburetor needs to be emptied after ever use.
 

daveznspace

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Re: slow in-gear speed on a 9.8HP TOHATSU

ok.... so soaked it over night, rinsed off and blew out n dry with compressed air, put it together and while certainly better its still only getting bout 1/2 power... so whats next?
 

TOHATSU GURU

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Re: slow in-gear speed on a 9.8HP TOHATSU

ok.... so soaked it over night, rinsed off and blew out n dry with compressed air, put it together and while certainly better its still only getting bout 1/2 power... so whats next?

Back to cleaning it again. The fact that it got better is an indication that you are on the right path. In the end the carb may be so damaged so that you have to replace it. It is also possible that something else is wrong. So, you go through the entire fuel system again, then you go through the ignition system and then you start looking at the mechanical side.
 

pvanv

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Re: slow in-gear speed on a 9.8HP TOHATSU

Right. Make sure that you completely disassembled every bit - emulsion tube, jets, etc. You can blow it out with spray carb cleaner, which is a great high-velocity blow-out for anything that was softened in the soak.
 

daveznspace

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Re: slow in-gear speed on a 9.8HP TOHATSU

Paul, I got the book you sent last night as well and one thing I noticed was that I had the 2 carb gaskets and insulator on the wrong side (which is how the last mechanic put it on) so that might have something to do with it. Also the manual says to use G17 on the inner gasket but I havent found any of that here yet, what else can you use? It doesn't look like they used anything last time.

It sounds like it used to, even that little "whine" it had when idling. When I get home I'll try switching the gaskets to the right end and find some good gas.
 
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