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Old 18-05-2021, 22:51   #1
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Tohatsu 9.8 four stroke starting problems

Hi there my name is Larry and I am new to your forum. I am looking for some help on a Tohatsu 9.8hp four stroke outboard I just purchased for my Lancer 28. The motor had been dropped and the cam pulley " driven pulley" got broken. I bought it that way and today I replaced the pulley and tried to set the timing but am not sure what marks to line up. My Honda B100 was so easy! I darn near wore my arm out trying to start this motor today. I cannot get it started! Hoping someone out there can give me the valve clearances and which valves are intake and witch valves are exhaust. The motor is a 2004 Tohatsu MFS9.8 Long shaft.



Things I have done:
Set timing with new pulley? questionable about timing marks

Compression 125 psi both cylinders
Good spark " Checked trigger voltage and exciter coil voltage
Replace plugs
Cleaned the carburetor twice
Plugs are dry with no signs of flooding. Primer bulb gets hard when I prime carburetor


I am lost as to why it will not start. Any help would be greatly appreciated!


You can also send response to my email which is hondalarry@yahoo.com


Thank you in advance for any help!!
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Old 19-05-2021, 05:04   #2
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Re: Tohatsu 9.8 four stroke starting problems

Welcome to the forum, Larry. Give me a minute to consider your question.
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Old 19-05-2021, 05:16   #3
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Re: Tohatsu 9.8 four stroke starting problems

It looks like you have to buy, as opposed to simply download, the service manual. Here it is for $17.

https://www.allservicerepairmanuals....EaAvZHEALw_wcB

Dry plugs after all that pulling implies lack of fuel. Have you tried a squirt of starter fuel, or even gasoline, as a diagnostic tool? If you get a VROOOM and it then dies, you're not getting fuel through the carb, cleaning or not.
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Old 19-05-2021, 20:41   #4
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Re: Tohatsu 9.8 four stroke starting problems

G
Quote:
Originally Posted by hondalarry View Post
Hi there my name is Larry and I am new to your forum. I am looking for some help on a Tohatsu 9.8hp four stroke outboard I just purchased for my Lancer 28. The motor had been dropped and the cam pulley " driven pulley" got broken. I bought it that way and today I replaced the pulley and tried to set the timing but am not sure what marks to line up. My Honda B100 was so easy! I darn near wore my arm out trying to start this motor today. I cannot get it started! Hoping someone out there can give me the valve clearances and which valves are intake and witch valves are exhaust. The motor is a 2004 Tohatsu MFS9.8 Long shaft.



Things I have done:
Set timing with new pulley? questionable about timing marks

Compression 125 psi both cylinders
Good spark " Checked trigger voltage and exciter coil voltage
Replace plugs
Cleaned the carburetor twice
Plugs are dry with no signs of flooding. Primer bulb gets hard when I prime carburetor


I am lost as to why it will not start. Any help would be greatly appreciated!


You can also send response to my email which is hondalarry@yahoo.com


Thank you in advance for any help!!
Get some brake cleaner spray a little in the carb then try starting. If it fires off, then it's not timing but carb. Clog.
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Old 20-05-2021, 08:10   #5
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Re: Tohatsu 9.8 four stroke starting problems

Buy the manual or set the cam/s at TDC with both valves of the top cylinder rocking. Pull out the top spark plug and you can put a screw driver in , slowly turn engine over and you can feel when TDC happens. Then rotate the cam shaft until both top cylinder valves rock evenly. If you feel any binding in the cam turn the crank back 1/4 turn, then set valves to rocking, then bring the piston to TDC.

At TDC the two valves should both be slightly moving. This is 180* out from when the engine fires and is typically how the valve timing is set.

Once you have the valve timing set you may or not have to swap the spark plug leads. Probably not.

Spray carb cleaner into the carb and see if it farts. Brake cleaner is not as volatile as carb cleaner of gas.
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Old 20-05-2021, 08:44   #6
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Re: Tohatsu 9.8 four stroke starting problems

Larry-

If you bought the motor in California, any fuel in the carb turned to goo, and you'd need to disassemble and clean. I'd give each cylinder a shot of WD-40, pop in the plugs, and give it a crank. That'll give you a quick rev if everything else is working.

I learned the WD-40 trick during my Jetski days-starter fluid is too volatile.
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Old 20-05-2021, 12:48   #7
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Re: Tohatsu 9.8 four stroke starting problems

If it is a lack of fuel issue, I would first try just cracking open the tank cap (not just the valve on the cap). I had fuel issues with my 6hp 4stroke Tohatsu. It was the "environmental no excess gas vapor leak "rubber valve in the tank cap causing all.the.problems. I ripped it out and happy running ever since. I always like to cross off the simple solutions first.
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Old 20-05-2021, 18:55   #8
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Re: Tohatsu 9.8 four stroke starting problems

Put in the safety clip LOL!
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Old 20-05-2021, 23:24   #9
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Re: Tohatsu 9.8 four stroke starting problems

https://www.manualslib.com/manual/99...hatsu-9-9.html

This should give you the info you need.
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