Tohatsu 9.9 Carb Conversion/Timing

[AJ316]

I have a Tohatsu 9.9 2 stroke, I believe it is a 1986 model? It has 9.9 D2 written on the recoil assembly which I assume was written when it was replaced. The carb was beyond cleanable and I could'nt find the parts for it anyways.

After a lot of internet research I found a "Carb conversion kit" which was supposed to include everything to convert my motor to the latest model carb so that it would be serviceable. I also had to change the intake housing.

The guy also mentioned he had the throttle cam to convert it to a 15hp, so I sprung and paid the extra $10 for that as well. I've attached pictures of the new cam (installed) and the old cam (in my hand). I would like to make sure than I actually got what I paid for because the new cam actually looks less agressive?

After getting it all installed I still cannot get the motor to run after a few pulls it will runs for a half a second and then cut off and sometimes almost backfire. I'm left wondering if I need to adjust the timing because of the new carb or cam? How do I adjust the timing if so?

I know that's mostly vague so if you need any more information about my motor to help me out just let me know and I'll try to post it.

Thanks ahead of time.

 

[AJ316]

Pictures wouldn't attach from my phone, hopefully they upload now.

 

[pvanv]

Year of manufacture is irrelevant, however, based on your case color, and suggested age, you probably have a B2. If you have a 9.9D2, yes, you can get a different throttle cam to convert to 15 hp. No carb swap is needed. The 15 hp part for the D2 is:

3M3637180M

THROTTLE CAM

$5.10

​For link and sync, see the Factory service manual (not aftermarket), available from any Tohatsu dealer. Yes, you need to adjust when changing all that stuff. Essentially, you set the throttle to Wide Open, then confirm the advance (at the parting line of the block), and confirm that the carb throttle plate is fully open.

The 15 hp part for the B2 is:

362637180M

THROTTLE CAM

$8.35

It appears that you have swapped for the D2 carburetor, so you probably need the D2 throttle cam.
You must have the air silencer installed for correct fuel mixture. It will not run, or not run properly, without it.

 

[AJ316]

So it sounds like since I have replaced the B2 carb with the newer D2 carb I will need to set timing to the stock settings for a D2 motor? Do you have any good links or videos on adjusting the timing?

Also I will check and upload the part # of the new cam he sent me. It's a possibility he sent me the wrong one as he accidentally sent me the gasket between the carb and the intake for the old style carb and. It the new carb.

 

[AJ316]

3G2031005M is the carb assembly 364637180M is the part number on the cam he sent me, does that seem correct?

 

[AJ316]

Also if I adjust the throttle rod to wide open throttle and set butterfly at 180 when you go back to idle the butterfly is still open about 1/4 of the way (note that I had to reuse the old throttle rod because he said that part wouldn't be in stock for a long time

 

[Sea Rider]

Have you changed the inlet manifold to install the newer D2 carb version ? Is the new cam already installed. Need to confirm if it's a 9.9 D2 model or a B2, both have different throttle cams and timing advance as well.

According to parts list D2 carb is 3G2-031-003, the one with 05 ending seems an older carb model or probably code has changed ?

Old 9.9 D2 throttle cam :



New 15 D2 throttle cam is 3M3-637-180.



Happy Boating

 

[ondarvr]

The timing doesn't need to be changed for it to run, only for it to actually reach peak HP with the new carb.

 

[AJ316]

Yes I changed the intake to the new style, also I changed the throttle cam back to the old one that was on it which looks exactly like your old 9.9 D2 cam Sea Rider, I was able to get full travel of the butterfly using the old cam on the new carb? Full throttle the butterfly is 180 and at idle it is closed.

When I was using the "15hp cam" he sent me it was either 180 at full throttle and at idle the butterfly was still open 1/4 or set the throttle rod at idle and it wouldn't open the butterfly to 180.

I'm thinking he sent me the wrong cam for this carb?

Using the new carb with the old cam I was able to get the motor to run shortly, I will be hooking it up to the water hose tomorrow to do more testing and tuning.

Can anyone send me any links or videos about adjusting the timing? The only thing I can see to do is adjust the threaded rods that connect the tiller handle to the timing fly wheel?

 

[Sea Rider]

You are doing Frankeinstein adjustments LOL!! What you need to do in order to conver a 9.9D2 into a 15D2 upgrade is :

-Change old cam for new one.
-Advance timing plate mark to 25 deg from actual 20-22 timing
-Synch/adjust throtttle rod height for carb to open fully when timing plate stops at 25 deg.

Won't find a video, Tohatsu won't like users modifying therir 9.9 into 15, as 15 costs bit more. This modification has been requested before check old posts 9.9 to 15 HP conversions. Probaly a Moderator can chime in to help search for it. Don't lose your time experimenting wild adjustments with 0 avail....Once found, if anything it's not clear to your plain understanding, just ask.

Happy Boating

 

[pvanv]

Have you changed the inlet manifold to install the newer D2 carb version ? Is the new cam already installed. Need to confirm if it's a 9.9 D2 model or a B2, both have different throttle cams and timing advance as well.

According to parts list D2 carb is 3G2-031-003, the one with 05 ending seems an older carb model or probably code has changed Happy Boating

Luis, The 05 carb is a newer revision. They start at 0 and go up.
364637180M is for the 9.9D2, not the 15D2. You do not have the correct cam.

 

[Sea Rider]

Paul,

For clarification second posted pic corresponds to the 15D2 cam which starts with code 3M3, needed if upgrading from a 9.9D2 to a 15D2 OB, 364637180M corressponds to a 9.9D2 cam which seems doesn't match the first posted pic at all.

Happy Boating

 

[coast2montana]

I have a Tohatsu 9.9 2 stroke, I believe it is a 1986 model? It has 9.9 D2 written on the recoil assembly which I assume was written when it was replaced. The carb was beyond cleanable and I could'nt find the parts for it anyways.

After a lot of internet research I found a "Carb conversion kit" which was supposed to include everything to convert my motor to the latest model carb so that it would be serviceable. I also had to change the intake housing.

The guy also mentioned he had the throttle cam to convert it to a 15hp, so I sprung and paid the extra $10 for that as well. I've attached pictures of the new cam (installed) and the old cam (in my hand). I would like to make sure than I actually got what I paid for because the new cam actually looks less agressive?

After getting it all installed I still cannot get the motor to run after a few pulls it will runs for a half a second and then cut off and sometimes almost backfire. I'm left wondering if I need to adjust the timing because of the new carb or cam? How do I adjust the timing if so?

I know that's mostly vague so if you need any more information about my motor to help me out just let me know and I'll try to post it.

Thanks ahead of time.

I am looking for the kit mentioned above. Does the original poster or anyone else have a link for a B2 to D2 carburetor conversion kit? Alternatively, does anyone know what it entails?

 

[GA_Boater]

I am looking for the kit mentioned above. Does the original poster or anyone else have a link for a B2 to D2 carburetor conversion kit? Alternatively, does anyone know what it entails?

It's a little hard to get an answer from an OP who was only active in the forum for 4 days back in 2016. Start a new thread to get answers from our current active members. Thanks.

Closed.