Nissan/Tohatsu throttle cam removal/upgrade to 15hp, timing question, w/p questions, dead CDI tip

[glassmancanada]

Nissan/Tohatsu throttle cam removal/upgrade to 15hp, timing question, w/p questions, dead CDI tip

Hey all, hopefully I can get a few questions answered here.

I have a Nissan NS12C and I have ordered the throttle cam for the 15hp 362-63718-0M. I cannot find any parts 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 on 9.9 to 15 hp conversion 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

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?

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?

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,




Pics show coil plate position and cam bolt position/interference



Timing at WOT


Timing at idle


Throttle levered full open showing carb tab stop



Throttle levered full open on carb tab stop showing throttle plate at 180 degrees


Throttle plate position @ WOT with stock cam





W/P liner and guide plate pics

 

[glassmancanada]

Also can someone help with the torque spec on the flywheel nut?

 

[glassmancanada]

Oh and if anyone has any tips for removing the water pump liner from the housing without damaging the housing that would be great.

 

[Sea Rider]

-After pulling black plastic linkage upward away from coil plate rod, disconnect rear electrical plate's cables adjacent to spark plugs for plate to turn freely CW or CCW, will access cam's nuts much better being sideways.
-4th pics shows your timing advance at around 20 deg. When will new 15 HP cam arrrive ?
-Assume it's wot position, right, If so, has roller reached the upper high hill on cam ? or resting at high hill base ?
-Impeller liner looks good, if still with lines, polish again with toothpaste and very used 3M green pad in circular motion.
-No need to remove liner from housing if won't be changed.
-12 HP cam seems different as of 9.9 newer cam, carb will probably not match bumping that engine to 15 HP, could have smaller fuel passages than newer 9.9/15 HP carbs? that 12 HPcarb is an old fashioned model.
All for the moment...

Happy Boating

 

[glassmancanada]

-After pulling black plastic linkage upward away from coil plate rod, disconnect rear electrical plate's cables adjacent to spark plugs for plate to turn freely CW or CCW, will access cam's nuts much better being sideways.

I disconnected the linkage at opposite end. The first pic shows max CW rotation, as you can see the bolts are over the intake and won't come out. The second pic is the opposite side of the motor, same coil plate position. This shows the coil plate tab hitting the fuel filter housing, even if I remove the filter housing it is not enough to get the bolts over open area. Third pic shows front cam bolt hitting tab on intake limiting CCW rotation. Looks like I have to remove the flywheel and coil plate to get the cam off? Torque spec for the flywheel nut?

-4th pics shows your timing advance at around 20 deg. When will new 15 HP cam arrrive ?

20 deg, does that go by the front side of the casting tab on block? Should I set it to 22 deg or bump to 25 deg with the new cam? Cam will be a bit before I get it

-Assume it's wot position, right, If so, has roller reached the upper high hill on cam ? or resting at high hill base ?

Are you referring to the stock cam pic at WOT? It is at the peak of the hill so to speak or just past it.

-12 HP cam seems different as of 9.9 newer cam, carb will probably not match bumping that engine to 15 HP, could have smaller fuel passages than newer 9.9/15 HP carbs? that 12 HP carb is an old fashioned model.

Yea according to the M9.9B2 manual etc the carb for 9.9, 12 and 15hp are exactly the same. The cam for 9.9 and 12 are the same interestingly enough, not sure how that works for the extra power. There were 2 carbs available for these and you are correct I have the older version. However the only difference in parts for the 2 carbs are the float and needle/seat so I see no reason to think it wont support the 15hp cam.

I've ordered a new impeller, should I use it on this liner and guide plate? Or while I'm at it replace them as well? Tips on liner removal if yes on replacement?

 

[Sea Rider]

To access cam bolts once timing rod has been removed, remove starter from flywheel (3 screws) must release electrical black sheath package that exits timing plate to plug side to have enough clearance to turn plate CW or CCW to better access cam bolts.

Better wait till new cam arrives to make a one whole job, if 12 HP works with 25? timing must advance plate by means of upper A stopper located at right side of advancer arm. Must freed small nut on screw prior turning it CCW for plate to travel to 25? position, once there adjust nut again for screw to remain tight against thread.

The line that forms both mating crankcase halves must be aligned to match timing plate marks at a straight line. Should stand yourself in front onf both mating surfaces line to match and later adjust properly A stopper. Don't have info for that old model, not sure if with 22? or 25? timing advance. Will need to know if existing carb is same for the 9.9 & 15 HP versions, could have restricted fuel passages and engine will perform awful no matter if having a new carb cam.

To remove liner from housing will need to turn it upside down and with a proper object start slight banging the round metal portion (where drive shaft exits) in circular motion till liner starts being pulled away from liner. Sometines is tricky to remove due being excesively stuck on housing. That liner looks mint, no need to remove it, with new impeller engine will pee as a teenager guaranteed.

Happy Boating

 

[glassmancanada]

Thanks for your input, I really appreciate it but I think you are misunderstanding me on the coil plate issue. I do not have a starter on my motor.
The electrical wiring disconnect is not the problem I have plenty of slack. If you review my comments and check the pics you can see that there is no way to rotate the coil plate further CW or CCW from where it is in the pics. The intake housing is in the way on CW rotation and the casting protrusion stops the plate from rotating further CCW
Regards

 

[glassmancanada]

Is this the edge of reference for timing showing just over 20 deg?

 

[glassmancanada]

Front cam bolt is hitting this casting protrusion limiting CCW rotation

 

[Sea Rider]

Yep red arrow point is at matting check point, ok about not being possible to rotate timing plate freely. Really haven't seen or serviced such an old 12 HP. Only work with newer 2 strokes 15-18 HP engines and the procedure is as described. Probably will need to pull flywheel off to remove timing plate and access both cam bolts. Anyway torque for flywheel nut is : 70-88 N-M

Happy Boating

 

[glassmancanada]

Perfect thanks!
Would anyone happen to have the timing spec for the M15B2 at idle and WOT?
Regards,

 

[Sea Rider]

15D2 Specs :

Wot timing mark 25?
Idle -3? leave it at 0? less throttle dead slack on tiller at idle.
Wot rpm range : 5200-5800
Gear rpm : 800 when going at idle.

Happy Boating

 

[glassmancanada]

Actually the green arrow tip is where the casting mates. Is this the timing reference mark? Or just the whole tab

 

[Sea Rider]

Can't tell visually, the reference is the middle line formed between both crankcase's halves mating surfaces. Stand at middle mating line, kneel a bit to have both aligned marks at front sight and adjust or readjust as needed. Don't finger with plate's rod adjustment, all adjustments must be done playing with stopper A located to the right of crankcase.

By the way, is it possible to move timing plate completely to the left, if so probably could access both nuts under plate without removing starter, flywheel & timing plate assy, check.

Happy Boating

 

[glassmancanada]

Ok, I set the timing at 22 deg WOT and 0 deg idle per your instructions on stopper A and B. I used an old xacto blade as my straight edge for alignment. How's it look to you?

 

[Sea Rider]

Looks good, how are you going to address the cam removal issue ? see if possible to turn plate to the left as there's that blue thing to the right. Your goal is setting timing advance to 25?, assume you are practicing the procedure, LOL!!

Happy Boating

 

[glassmancanada]

You still recommend 0 deg for me on idle timing when cam is changed? Or even before cam is changed? I noticed when I set to 0 deg the cam is already acting on the throttle plate. How much will this increase my idle rpm? Pic below of gap on idle set screw now and position of cam on roller.





I called Nissan USA and asked for timing spec on M15B2 and he couldn't find anything in the books so he asked a long time mechanic and he recommended the standard 22 and -3 just to be safe. I guess I could try the 25 deg after I try out the new cam and see how it runs first. Likely have to be careful of pre detonation?

I have the blue protrusion in the casting hitting the bolt turning left and plate lever hitting when turning right. I'll have to pull the flywheel to change the cam.

Regards,

 

[glassmancanada]

Should I adjust the rod to get the throttle plate position back on the set screw stop with the new cam?

I think once I get the new cam there will be a gap there regardless and the plate would be on the stop again if I remember right from the other thread.

 

[Sea Rider]

You need to install new cam firstly, it's useless having fun with engine as new cam will probably vary carb timing. That will be addressed later once have swapped cam. Will make no difference if set at 0 or -3 deg as carb is still working on ralenti/idle, roller is not touching cam at extreme right end portion. Cam will begin to actuate roller when throttle grip marks face each other, as when starting the engine not before.

Happy Boating

 

[glassmancanada]

I notice in my previous pic with the green arrow as timing reference my initial timing was set to 18 deg @ WOT. I wonder if that's how they de-tune the engine? Maybe that's how they get 9.9 hp on the same throttle cam is by lowering the WOT timing/ max throttle.