Tohatsu 9.9 to 15 conversion question

[inkd_dad]

I have a Tohatsu 9.9 (M9.9B2 to be specific) and ordered the the conversion cam for the carb from internetoutboards.com (quick shipping BTW, good experience).

I installed the cam and adjusted the throttle arm rod at WOT so that the butterfly plate is 180 degrees and there is a very slight amount of pressure on the throttle roller.

Then when I back the throttle off there is a gap between the cam and the throttle roller... is this normal?

I have not taken it out yet, but hope to this weekend. Any help or reassurance is appreciated!

 

[pvanv]

Re: Tohatsu 9.9 to 15 conversion question

Yep, not unusual. When at idle, the idle stop screw locates the throttle plate to provide the correct idle.

 

[Sea Rider]

Re: Tohatsu 9.9 to 15 conversion question

A proper adjustment of the cam and throttle roller at wot (pic 1) would be to turn roller freely with fingers once against max cam angle. Add a drop or 2 of thick oil on the roller shaft to minimize unwanted wear.

Happy Boating

 

[inkd_dad]

Re: Tohatsu 9.9 to 15 conversion question

Thanks gentlemen. Great information and glad to know it's not abnormal. Will take it out this weekend and enjoy my new hotrod.

Jay

 

[Sailor18]

Re: Tohatsu 9.9 to 15 conversion question

inkd_dad - how did it work out? My 9.9c has the same conversion, however I did not mess with the throttle arm rod. So I have the opposite situation as you - there is no gap between cam and throttle roller when the throttle is closed.

I do have a problem as the butterfly approaches wide open though. As it does I lose power. However I noticed that the service manual shows the following:

Throttle opening (at W.O.T.) 18D/15C 72deg 9.9C 53deg

So I am curious to know how well your 9.9 ran at W.O.T (assuming the butterfly is perfectly level). Not sure if I need to adjust the throttle arm rod.

 

[inkd_dad]

Re: Tohatsu 9.9 to 15 conversion question

My manual for the 9.9b shows no difference in timing between the 9.9 or the 15. Motor ran well after doing the conversion, from idle to WOT. I have a speedometer accessory I installed for my fishfinder and I topped out at 23 mph (Valco 12ft, 2 people, ice-chest, 6 gallons of fuel). So I am going to switch back to 9.9 and run it again and see how it works out. I will report my findings.

In your case I highly suggest setting your throttle arm based on WOT and testing. Let me know how it goes.

 

[Sailor18]

Re: Tohatsu 9.9 to 15 conversion question

Thanks for the help. My manual also does not show any difference for the timing between the 9.9c and 15c -

ATDC 3deg - BTDC 22 deg

The info. I previously posted was in another section of the specifications that I had not noticed before. It has to do with the throttle opening (??? the angle of the butterfuly???).

At any rate, from what you're telling me your 9.9b ran fine with the upgraded cam and butterfly fully open.

Just short of WOT my 9.9c loses power. I top out at 19mph (using a GPS) on my 12' aluminum jon boat (w/ two persons). I'm not sure my 9.9 is tuned right. I am thinking it has to do with the synchronization of the butterfly and throttle cam.

From your previous posts I am assuming you did not adjust the advancer arm adjustment stoppers - correct?

I am curious to know what you find out.

Thanks again.

 

[inkd_dad]

Re: Tohatsu 9.9 to 15 conversion question

Not sure what the advancer arm adjustment stoppers are but here was my process.

In the first photo there is a brass collet to the right of the throttle roller. If you loosen the screw on that brass collet it releases the butterfly from the throttle roller allowing adjustment. Turn your throttle to WOT, look down the venturi and move the butterfly arm until it is at 180 degrees to the venturi and tighten the screw on the brass collet. Now when you turn the throttle back down it will look like the second photo with a space between the throttle cam and the roller. This is how I ran my motor at the lake and it ran fine, but it had been too long between when I had it set as a 9.9 for me to notice too much a difference and I never had a speedometer when I had it as a 9.9 so that is why I am going to switch it back and check it out. Hope this explanation makes sense.

My fear for you is that if you did not loosen the brass collet at all after installing the throttle cam that you are ramping up too quickly to WOT.

Jay

 

[wxyzed]

Re: Tohatsu 9.9 to 15 conversion question

I see how the conversion works for a 9.9 to a 15. My question is will the same process work for an 18hp; if so would it convert to a 25? All replies are appreciated. I am new at outboards and am still learning computers.
Thank you.

 

[TOHATSU GURU]

Re: Tohatsu 9.9 to 15 conversion question

No. The engines have nothing in common. You need to understand that when people talk about boosting up their hp what they are really doing is returning a detuned model to its original designed hp. IE A manufacturer builds a 15 and will then detune it down to a 9.9 or a 50 is detuned down to a 40. Its cheaper to design and build a hp and reduce it rather than build a different engine for each hp. Other than severe custom work you cannot boost hp over a point or two above design parameters.

 

[Sailor18]

Re: Tohatsu 9.9 to 15 conversion question

"My fear for you is that if you did not loosen the brass collet at all after installing the throttle cam that you are ramping up too quickly to WOT."

I got it. That was pretty much it. Now the position of the throttle cam roller on my 9.9c looks pretty much like yours. I took it out last weekend and it runs fine. Doesn't really get more power just ramps up properly without loosing powerr at WOT.

Evidently the butterfly was opening "too soon". I got the motor second hand and whoever had it first had it all screwed up - the timing was way off, the throttle adjustment was all screwed up, it was a mess. Now it's clean and idling better than it used to...by far...

Thanks for the help -

 

[jeaniturrizaga]

Re: Tohatsu 9.9 to 15 conversion question

Hi, I just got one of this little outboards and I'm thinking of doing this conversion, but I keep reading here and there that there is no noticiable change after doing it?? also is there anything else that needs to get done other thatn the trottle cam swap?, ohh by the way I'm the proud owner of a inflatable Achilles HB-310 fiberglass hull, I just upgrade from a kayak, so I'm still learning a bit. thanks guys!!

 

[TOHATSU GURU]

Re: Tohatsu 9.9 to 15 conversion question

"I keep reading here and there that there is no noticiable change after doing it?"

Stupid people say stupid things like that all the time...Don't pay any attention to them. There is a measurable 5 hp difference at the prop at WOT.

"also is there anything else that needs to get done other thatn the trottle cam swap?"

No

 

[Sailor18]

Re: Tohatsu 9.9 to 15 conversion question

All you need is the cam. I eventually figured out that the timing was screwed up. Just get the cam and make sure your timing is dead on. Strictly by the numbers the upgrade should give you the added HP.

 

[Buzz457]

Re: Tohatsu 9.9 to 15 conversion question

I know this post has been resolved for most of you, but I have a 2004 Nissan 9.9 4stroke (NSF9.9B2) that I just bought used. I wanted to know what to do to increase it to a 15 or what to look for if the previous owner had done any modifications. I am going to change all the fluids and plugs this week and test run it hopefully. If everything goes well, bumping it up will be next on the list. Thanks for any help.

 

[pvanv]

Re: Tohatsu 9.9 to 15 conversion question

This really belongs in its own thread, since it's a completely different motor. But... You can bump that motor to a 15 with a different carb. FWIW, you can bump it to 18 hp if you also change the cam and intake silencer, and associated bits.

 

[Buzz457]

Re: Tohatsu 9.9 to 15 conversion question

Thanks, I'm sure when I get it going as a 9.9 I'll be on here picking the experts to get the most out of it.

 

[razzle]

Re: Tohatsu 9.9 to 15 conversion question

Hey guys sorry to bring this up but has anyone got pictures of the two cams side by side.

Thanks
Rian.

 

[Sea Rider]

Re: Tohatsu 9.9 to 15 conversion question

Hola Razzle,

Which 9.9 model do you have, bear in mind that there are 9.9D & 9.9 D2 and if wanting to convert you have a 15D & 15D2, all 4 have different timming marks, so it's not that simple as to swap cams if wanting a correct update to count withl 5 HP difference. Both 9.9 & 15 cams are completely different.

Happy Boating

 

[TOHATSU GURU]

Re: Tohatsu 9.9 to 15 conversion question

Look at the first picture in the thread. That shows the 15 hp cam. The 9.9 cam comes out like the mid point on the 15 cam and then goes across. You can check the internetoutboards.com site and see if they still have the images up on them.