Tohatsu 70hp Timing (model M70A)

pvanv

Admiral
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Apr 20, 2008
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Paul, thank you very much. The Tohatsu 2.5-140 HP is a 1992-2000 Clymer manual. I also have a 1 & 2 cylinder Tohatsu manual 3210351 that only goes up to 40HP motors. I ordered a Nissan Manual with the NS70A that got lost in the mail, so I ordered a Tohatsu "TOHATSU NISSAN M55B 353 M70A OUTBOARD MOTOR ENGINE SERVICE SHOP REPAIR MANUAL". I am assuming that the MS70A and the M70A is the same engine.

Yeah... the Clymer manual is best relegated to being tinder for the woodstove this fall.
 
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pvanv

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The original post was asking about setting the timing on a M70A engine which is a 2 cylinder. The M70B is a 3 cylinder. I have a NS70A which is a 2 cylinder and I am assuming is the same engine as the M70A. Both have "360-1" to start the serial number. I purchased this engine not working and somebody replaced a lot of parts on it. The guy that sold it to me said there was a spring he found laying there with no idea where it went and it is now lost anyway. I have not seen any diagrams showing a spring. The part with the timing marks has some play in it, so I thought it may go up under the fly wheel, but I am not sure. I replaced the fuel pump and the CDI unit and the motor will fire up and run at fast speeds if I play with the throttle link between the 2 carburetors. When I let them return to idle, the engine stops. Compression is good and I cleaned the carburetors. The fuel jets are adjusted at 1 turn and I have played with them also. The engine seems to fire up when I first try to start it. When I continue to try and start it after it has died, it does not even try to start. If I spray starting fluid though it will fire. It seems to me it has something to do with the fuel not getting through the pump..I know there is also this reed block assembly, but I do not know if those can go out of adjustment.

Yes, the NS70A and M70A are identical aside from paint.
No clue about the spring. Nothing like that under the flywheel.
Reeds seldom fail.
Odds are the carbs need to be Properly cleaned. I start with the pilot screw at 2 turns.
Clearly too lean, as ether spray makes it run.
 

natvalve

Cadet
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Jun 13, 2020
Messages
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Thanks Paul, I got the Tohatsu Service Manual today and I am checking all of the linkage adjustments. I had the carburetors off and cleaned them on my kitchen table. I also was going to do some tests on the fuel pump to see if that is the problem. I purchased a 12 volt fuel pump. Has anybody ever tried converting to an electric fuel pump?
 

pvanv

Admiral
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Apr 20, 2008
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No. The diaphragm pump is very reliable. a 12v pump needs a stalled-disconnect for safety.
 

natvalve

Cadet
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Jun 13, 2020
Messages
6
I noticed that in the manual it shows a check valve in the fuel line. It does not tell me where this is though. The diagram looks like it is in a flange with 2 screw holes. I have not seen anything like this on my engine.
 

pvanv

Admiral
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There is a check valve for the oil recirculation line. Is that it? AFAIK, no check valves in the fuel line...
 

MarcoPW

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Nov 16, 2022
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Thanks for the info, I was surfing the net for timing specs and found it here. 👍
Thanks for sharing!!
 
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