Tohatsu 9.9hp to 15 hp?????

[rockfordhx]

I recently purchased a used Tohatsu M9.9C and someone told me that there was a upgrade that could be done to boost the hp from 9.9 to 15. Is this information correct?

If so does anyone know what the part number is?

thanks
-N

 

[TOHATSU GURU]

Re: Tohatsu 9.9hp to 15 hp?????

http://www.internetoutboards.com/partdetail.asp?id=505

 

[rockfordhx]

Re: Tohatsu 9.9hp to 15 hp?????

Thank you Elvin.

2 quick questions though. The part that you linked to says "This part is used to convert 9.9 D2 models down with serial numbers lower than 71413. It will not work on serial numbers above 71412".

1. Will this still work with the 9.9C?
2. I noticed when the cowling was off and the throttle was all the way open (90 degrees) that that the butterfully was all the way horizontal. How does this part work?

thanks !!!!!!!!!
-N

 

[TOHATSU GURU]

Re: Tohatsu 9.9hp to 15 hp?????

1) C is below D so yes, it will work.

2) The cam opens the butterfly up...It sounds like your engine has already been converted.

 

[rockfordhx]

Re: Tohatsu 9.9hp to 15 hp?????

Thanks Elvin. Anyone have a picture of the part so that I can verify that the conversion has been done?

 

[Sailor18]

Re: Tohatsu 9.9hp to 15 hp?????

Elvin!!!! Or should I say TG? It's me, Conrad (you know the guy who visits every week and buys parts I don't need for too much)

Hey btw - rockford is my brother. We got the motor humming nicely (thanks for the parts). It's even clean and pretty looking.

I took it out today and gave it a spin. It worked great with one exception - as the throttle is advanced, just before it reaches WOT, the motor starts to loose power, the RPM's drop and the engine starts to sound like it's struggling.

Wide open the speed and rpms are lower than when the throttle is about 75% open.

We were using a GPS and just short of WOT we were doing about 18-19mph and then as the throttle is advanced the rpms would drop and we slow down to 14-15 mph. I took the cowling off and observed that the butterfly was not fully open at 18-19 mph and then as the cam advanced further (opening the butterfly further) the rpms dropped as did the speed.

Is this a timing issue? Perhaps the carb is delivering too much fuel? I'm at a loss here.

IF the 9.9C gets the cam upgrade, does the CD unit need changing? Is it firing fast enough?

While underway I tightened the screw on the top of the carb(I believe it controls the idle) as much as I could without stalling the engine - and no luck there.

Any ideas?

-Conrad

 

[TOHATSU GURU]

Re: Tohatsu 9.9hp to 15 hp?????

The butterfly tells all. It should be fully open when the throttle is fully advanced so it sounds like a linkage/adjustment issue. I would check the timing, but, it can't come out of adjustment by itself. Same CD, so unless its bad, that wouldn't be the problem. The trigger coil or exciter coil could have an issue, but its more than likely that it just an adjustment.

 

[Sailor18]

Re: Tohatsu 9.9hp to 15 hp?????

Perhaps it was the timing...

I had assumed the timing hadn't been messed with however once I started reading the rest of the service manual (I skipped this section the first time) I noticed that when the tiller handle was turned fully counter-clockwise the timing indicator marks on the magneto coil plate were only showing 16 - 18 degrees, versus the 22 degrees shown in the service manual.

I backed out the screw that allows the coil plate to advance further and noticed that there was some white lock-tite screw adhesive type stuff on the screw. After backing out the screw far enough to allow the coil plate to advance to 22 degrees, I noticed that the white stuff on the screw more or less lined up to where it had been originally (from the factory I guess). That sort of confirms for me that someone had cranked it in.

I started it up and it sounds right. I need to get it in the water to test it under load. I'll try later this week and let you know.

Hey I did notice one thing that seemed odd to me though. The last 5 degrees or so that the coil plate advances - the throttle is wide open - it has reached the flat portion of the throttle cam. So the coil plate still rotates a bit further but the butterfly doesn't open anymore as it is fully open. Does this sound right?

-Conrad