Tohatsu 9.9 d2 ignition timing

[Branchtree]

Hi everyone.

I would like to get a clarification regarding the ignition timing (this seems to be the best and complete thread for it).
I have seen the pictures posted above but the mark to set the timing to seems very poorly made.
My outboard is a tohatsu 9.9 d2 from 2004 and some previous owner/mechanic have installed to 15hp cam and the throttle is absolutely opening 180 degrees.

The timing though, it's looks like 22-23 ish?
Hard to tell.

Should you measure from the center of the marker or left/right?

In an older thread there was a picture of the timing and how the 9.9 and 15 was on WOT.
I thought it would be good to gather all info in one place but I was ordered to create a new thread.

 

[pvanv]

3m3637180m

throttle cam

$13.00

This will convert your 9.9 to a 15.
Full timing info is in the Factory service manual.

 

[Branchtree]

3m3637180m

throttle cam

$13.00

This will convert your 9.9 to a 15.
Full timing info is in the Factory service manual.

It's already converted and I have looked at the service manual.
My questions remains the same

 

[Sea Rider]

You want to convert your 2 stroke Tohatsu 9.9 D2 to a 15 D2 right ? The 9.9 D2 comes factory adjusted to BTDC 20°, the 15 D2 to 25º with installed new throttle cam. At your current setting the timing mark is around 22-23º need to rotate the timing plate CCW 1, 2º + till the plate stops right at 25º, that's middle line of both mating surfaces line as in pic.

​

What you can do is : With throttle grip set to max rabbit side, disconnect the rod joint push it up, rotate plate CCW to 25º, once there hold it, readjust the "rod joint" CW to decrease the link rod distance so when the rod joint is reinstalled with less length will match the 25º mark right at middle of both mating surfaces.

Once all is OK, throttle back to min turtle side. Throttle slowly to max range and check carb, must be fully opened to 180º with timing plate stopping at 25º. Probably will need to readjust the carb's vertical rod height for timing advance and carb to fully match both settings. Report your findings....

Happy Boating

 

[Branchtree]

You want to convert your 2 stroke Tohatsu 9.9 D2 to a 15 D2 right ? The 9.9 D2 comes factory adjusted to BTDC 20°, the 15 D2 to 25º with installed new throttle cam. At your current setting the timing mark is around 22-23º need to rotate the timing plate CCW 1, 2º + till the plate stops right at 25º, that's middle line of both mating surfaces line as in pic.

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What you can do is : With throttle grip set to max rabbit side, disconnect the rod joint push it up, rotate plate CCW to 25º, once there hold it, readjust the "rod joint" CW to decrease the link rod distance so when the rod joint is reinstalled with less length will match the 25º mark right at middle of both mating surfaces.

Once all is OK, throttle back to min turtle side. Throttle slowly to max range and check carb, must be fully opened to 180º with timing plate stopping at 25º. Probably will need to readjust the carb's vertical rod height for timing advance and carb to fully match both settings. Report your findings....

Happy Boating

Hi.


The outboard has already been converted as far as I know (except the timing apparently).
The cam is there (see attached picture) and the butterfly opens 180° with the carb stops touching.

The thing I'm wondering about is what surface should line up with the 25° mark (see my next picture).
The service manual (it's from 2007 and describes the smaller C-engines and larger D-engines, so 3 years newer then my outboard) says nothing about this so I'm guessing it's center as you mentioned.

The next pictures are from the manual where I have highlighted how I adjust the timing at WOT.
Last picture is how you adjust idle timing if someone in the future is wondering.

 

[pvanv]

The line where the block halves join is the line you want.

 

[Sea Rider]

If the white roller is already resting on the upper cam hill at full throttle as in first pic, don't mess with number 3 shown in third posted pic, simply advance the timing plate tad more to the middle line formed between both mating halves as suggested.

Happy Boating

 

[Branchtree]

The line where the block halves join is the line you want.

If the white roller is already resting on the upper cam hill at full throttle as in first pic, don't mess with number 3 shown in third posted pic, simply advance the timing plate tad more to the middle line formed between both mating halves as suggested.

Happy Boating

Thank you guys for the patience.

I think this will be it's final resting place. 25-ish degrees from the mating surface.

 

[Sea Rider]

Congrats, perfect match. Our patience is near unlimited LOL!!



Which boat size and type will be powering the converted Tohatsu with, how many souls will be on board ? Have some outstanding tips to get the max HP out of it. If interested let me know...

Happy Boating

 

[Branchtree]

Congrats, perfect match. Our patience is near unlimited LOL!!



Which boat size and type will be powering the converted Tohatsu with, how many souls will be on board ? Have some outstanding tips to get the max HP out of it. If interested let me know...

Happy Boating

It's a 310cm inflatable rib (10 feet).

It has it's original propeller (8.5) that is between light and heavy loads and I suspect that I might overrev the outboard.
Ordered a tach to see if that's the case.

The hole-shot is amazing and the top speed is 20.5 knots with two people and 30 kg (65 pounds) of gear and fuel. That was before I/we fixed the timing.

Depending on what the tach say I might go up on pitch on the propeller

 

[Sea Rider]

A 8.5 pitch will surely rev near its max wot rpm range, a tach will tell. After finishing the max wot test idealy on flat water cond, pull head side of motor and check at which lower leg height is water flow passing by between both plates. Motor/ transom height optimization and a spot on prop maximization it's the way to go to get the max HP cowl rated out of the motor.

Happy Boating

 

[Branchtree]

A 8.5 pitch will surely rev near its max wot rpm range, a tach will tell. After finishing the max wot test idealy on flat water cond, pull head side of motor and check at which lower leg height is water flow passing by between both plates. Motor/ transom height optimization and a spot on prop maximization it's the way to go to get the max HP cowl rated out of the motor.

Happy Boating

Thanks for the tips, appreciated.

I guess that I can go for the 15d2 rpm range instead of the 9.9d2 now that it's been converted by the books?

 

[Sea Rider]

Thanks for the tips, appreciated.

I guess that I can go for the 15d2 rpm range instead of the 9.9d2 now that it's been converted by the books?

Yep, both 9.9 and 15 shares the same 250 CC powerhead . My 18 is rated at 5800 max but can run to 6 K for long time periods and hasn't been blown so far.

Happy Boating

 

[Branchtree]

The story continues.

Tried the new prop for the first time (9 1/4 * 10 1/2) and didn't gain speed nor rpm.
It sat around 5100 rpm at WOT around 18.5 knots.

Changed to the original prop (8.5 = 9.2 * 8.8) and got 1 knot more and around 100 rpm more.

Why doesn't the outboard rev more with the 8.5 prop?
Seems unlikely that I need to lower the pitch even more?

The trim angle was identical and is perfect.

 

[Sea Rider]

Troubleshooting issues :

-Before adjusting the new timing advance to 25º, do you recall at which max wot revs was the motor revving at ?

-Which is the current induction tach brand, was the firing sequence previously set at 180º, 2 spark per revolution ?

-Does the motor revs evenly through the whole throttle range, just doesn't achieve more rpm at max grip ?

-That's the 310 Sib, right ? Is it an alum or air deck flat or V keel one ?

-Were the tubes and keel inflated to the factory recommended working pressure with a pressure or thumb gauge ? A badly inflated small sib achieves more hull drag compared to a fully inflated one.

-Was the test done solo or with one + boater ?

-Was the trim angle previously set to 90º (fully vertical) what about the motor/transom height, any water splashes back or side of lower leg, prop aeration at close turns, choppy wavy water conditions ?

Will be good for said motor to go for a decarbon process with CRC Engine Tune-Up. Check procedure : Post 36

https://forums.iboats.com/forum/eng...n-outboards/10889250-1997-m40c-stalling/page3.

Happy Boating

 

[Branchtree]

-Before adjusting the new timing advance to 25º, do you recall at which max wot revs was the motor revving at ?

Sadly, no. I didn't have a tach at that time.

-Which is the current induction tach brand, was the firing sequence previously set at 180º, 2 spark per revolution ?

I don't recall what setting I had. Is the one you mentioned above the correct one?
It's a cheap amazon one;
https://www.amazon.co.uk/dp/B0756VGDTC/ref=pe_3187911_185740111_TE_item

-Does the motor revs evenly through the whole throttle range, just doesn't achieve more rpm at max grip ?

Yes, I would say so. It doesn't happen very much when you hit the last cam "hill".

-That's the 310 Sib, right ? Is it an alum or air deck flat or V keel one ?

It's a rib. Glass fiber with level floor, 59 kg/130 pounds.

-Were the tubes and keel inflated to the factory recommended working pressure with a pressure or thumb gauge ? A badly inflated small sib achieves more hull drag compared to a fully inflated one.

I believe so. No pressure gauge though.

-Was the test done solo or with one + boater ?

2 persons with 10kg/22 pounds of gear. Same on both tests.

-Was the trim angle previously set to 90º (fully vertical) what about the motor/transom height, any water splashes back or side of lower leg, prop aeration at close turns, choppy wavy water conditions ?

Trim angle is at hole two, that gives the best speed at the moment. At hole one I think that the front dives a little to much.
No splashing.
Transom height is only visually checked at WOT and the water is at the higher plate.

Will be good for said motor to go for a decarbon process with CRC Engine Tune-Up. Check procedure : Post 36

https://forums.iboats.com/forum/engi...stalling/page3.

Happy Boating

​​​​​​​Will, check it out.

 

[Branchtree]

[No message]

 

[Sea Rider]

Congrats, perfect motor/transom height match. Thanks for posting, that upper lower leg's plate setting for Tall Plates Gap Outboards achieves the best prop thrust at all water conditions and at close tight turns at speed provided that the OB sits at 90 deg on transom and deck load is evenly distributed for boat to run parelell to the water level. Will only need to have that OB running strong and from there to a spot prop maximization for OB to run towards its max 5800 wot rpm range as usually loaded.

The so called EV plate must be set around the boat's bottom only works well with Bolt-On OB's/Short Plates Gap OB's, but the general boating consensus of this and most boating forums states the contrary due to total ignorance by throwing both types of OB's in same sack...

Happy Boating

 

[Branchtree]

I'm back!

I got the engine tune-up can but haven't been able to use it yet (we have four seasons here and right now it snowing outside......).

BUT, I got an amazing deal on a m18e2 from -06 (the 9.9s are more valuable then the 18s here so I will probably get some money back).
Same weight as my 9.9 but bigger bore = more hp.

The RIB is only rated for 15hp but have can take a 60kg outboard.
3hp more isn't a big deal in my opinion.

This might be the wrong thread but what is a normal compression on a 18e2?
Cold, luke warm or hot when testing?

 

[Sea Rider]

My beloved M18E2 with near 1 K run hours still achieves 118 PSI on both cylinders when tested cold. It's mostly due to run CRC Engine Tuner every 100 worked hours along a full internal crankcase mechanical decarbonization every 300 to 500 run hours depending on use which nobody does and it's stated in the Tohatsu Service Manual...​

Happy Boating