Tohatsu 9.9 to 15 conversion question

seahorse77

Cadet
Joined
Feb 1, 2012
Messages
6
Re: Tohatsu 9.9 to 15 conversion question

SeaRider,

Sudden problem before prepping for the conversion;
my 9.9 after 3 hrs of motorsailing just konked out...
this after I cleaned the carb, fuel filter. Kill switch?

As I know this thread is for conversion alone, and
since you seem to have sound knowledge here
perhaps you can email me at Thyme@youthvault.org

I'll search for another thread for that too. thnx.
 

wasup005

Recruit
Joined
Jul 20, 2011
Messages
3
Digging up an old thread here, but I have a question directly related to the tohatsu 9.9 to 15 conversion. A few years back I stumbled upon and picked up a cheap used tohatsu M9.9B2 for a hardbottom dinghy, and it has been the best tiller motor I have ever dealt with, after going through a whole slew of small outboards that were either hard to start, didn't run good etc etc. This gem starts on second pull whether its been sitting at the dock or coming out of winter hibernation. My question is how do I know if I already have the conversion throttle plate installed? When I bought the motor, the guy said he did "an update" to it, but at the time I had no knowledge of the idea that you could simply convert a 9.9 to 15hp with just a few adjustments or a conversion plate, thought he was just blowing smoke. Are there any numbers or profiles depicted on a 9.9 throttle plate vs. a 15hp? I'm going to do a little spring overhaul- plugs, clean the carb etc, and would like to add the throttle conversion if I don't already have it. Any help is appreciated.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Both cams are quite different, one just throtttles to medium cam distance and then flattens out, the other goes to the near full extreme with a short flat out on cam's extreme. Will need to advance timing in order to have a complete 180° flat butterfly to let more fuel in. Post a pic of actual cam would be faster for a proper tech answer.

Happy Boating
 

wasup005

Recruit
Joined
Jul 20, 2011
Messages
3

photo1.JPG
Here's a couple snapshots of the throttle cam plate.
 

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Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Sorry Mike,

Can't see any posted pic, system still with tech flaws. Is it possible to know the last letters side attached to 9.9 Say 9.9 D, 9.9 D2 whatever ? Will indicate its timing advance. Usually slight less along diffrent cam shape angle & lenght to detune both current 250 CC powerheads from 15 to 9.9 HP model.

Better read the first posts regarding this thread, will see attached both cam shapes, angles & length physical differences. So which one did you buy ? is it possible if being a second hand engine that previous owner already changed it and only needs some slight + timing advance adjustment ?

Happy Boating
 

wasup005

Recruit
Joined
Jul 20, 2011
Messages
3
The pictures look like they load up from my end. I'll try one more time loading the pics. Either way, I did buy it used, and was told it had the "update", which now I assume is the throttle plate. The model is M9.9B2, serial number is 355A 22xxx if that helps at all. With that said, if I do have the 15hp throttle plate, what should the timing be advanced to? Whats the proper way to adjust?

Thanks
Mike

 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Welcome to Iboats,

There should be a sticker at outter side pan indicating the model.

The conversion basically involves 3 issues :

1-Cam swap from 9.9 to 15 HP model
2-Timing advance check.
3-Cam rod height.

If swapping cam, but 2-3 out of adjustment won't have a upgraded 15 HP horse.

Happy Boating
 
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glassmancanada

Seaman Apprentice
Joined
Aug 10, 2015
Messages
33
P1050310.JPG P1050312.JPG P1050311.JPG P1050313.JPG P1050314.JPG P1050316.JPG P1050319.JPG P1050320.JPG P1050318.JPG P1050317.JPG P1050322.JPG P1050324.JPG P1050323.JPG P1050315.JPG Hey all, sorry to revive from the dead but better than starting a new thread on the same subject.

I have a Nissan NS12C and I have ordered the throttle cam for the 15hp 362-63718-0M. I cannot find any part manual for this engine but I have gone through the Tohatsu parts manuals and it seems my engine is identical to the M12C2, M9.9B2, M15B2.

Anyhow, I've read through the thread and I have a few questions.

I removed the linkage to the coil plate assy as advised to get the cam bolts out but I cannot get the coil plate to rotate enough, intake casting is in the way. Do I need to remove the flywheel and coil plate? Pics attached

Could someone take a look at my w/p liner and guide plate and give their impression of condition? I polished them with crocus cloth but should they be replaced along with the impeller due to step wear?

Also could someone verify the timing settings on my engine? I bought it used but I'm having a hard time telling where it's set and what the reference mark is. Pics attached of idle and WOT positions. Do I need to bump the timing to 25 degrees at WOT as some have suggested?
I included pics of my throttle plate position when the cam is fully levered and it appears to be fully opened at 180 degrees to the bore determined by the stop on the carb. Will I still need to adjust the lever once the new cam is in?

On an unrelated subject I wanted to offer a tip that I discovered on faulty CDI boxes. Not sure if this is common knowledge but it saved me $260.00 so I wanted to pass it along. When I bought this engine I had a no spark fault and it wouldn't run. Determined it was a dead CDI and found it was $260.00 to replace!! I happened on a youtube vid at the last moment before ordering a new one where the guy was claiming the 75% of them could be saved by baking in the oven at 300 F for 10 minutes. Apparently what happens is the epoxy fill underneath the CDI separates from the casing and moisture gets in. It cannot evaporate as the casing holds the moisture in at the top. By turning it over and putting it on a pie plate in the oven the moisture is cooked out and the CDI works again. I did this and it worked like a charm, sealed up the bottom with shoe goo and also glued around the wire grommet so the moisture cannot get back in.

Regards,
glassmancanada
 

GA_Boater

Honorary Moderator Emeritus
Joined
May 24, 2011
Messages
49,038
Hey all, sorry to revive from the dead but better than starting a new thread on the same subject.


Regards,
glassmancanada

Right. We do prefer not reviving old threads. Click on the Forum Help link in the sig below.
 
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