2007 90HP Yamaha 2 stroke Idle Problems

[99yam40]

Advance the timing is what I wrote Could you send a picture of the switch that tells the CDI that the motor is warm? I am curious to see what it looks like.

To Robert Graham and mudfunk: Can you write here when you fix this problem and how you did it, I want to fix mine too.

actually you wrote "

The CDI retards the timing during the 40-45sec period after startup"

here is what my C40 has part #11 is for warmed up motor and #12 is for over heat
https://www.boats.net/catalog/yamaha...x/electrical-1

but I have no idea if your motor is the same or what your motor is, or if any of the 90s are the same as my C40

[holmen78]

actually you wrote "

The CDI retards the timing during the 40-45sec period after startup"

here is what my C40 has part #11 is for warmed up motor and #12 is for over heat
https://www.boats.net/catalog/yamaha...x/electrical-1

but I have no idea if your motor is the same or what your motor is, or if any of the 90s are the same as my C40

I don’t want to argue, but what I meant was that the CDI is retarding the timing from 12 BTDC to 6 ATDC during that 45 sec period, until the engine idles normally. At startup it advances the timing to 12 degrees (if I remember the numbers right), and drops from there. This happens with every startup.

Interesting that you have 2 of those switches, on a 90hp there is only one for over-temp alarm.

[99yam40]

I don’t want to argue, but what I meant was that the CDI is retarding the timing from 12 BTDC to 6 ATDC during that 45 sec period, until the engine idles normally. At startup it advances the timing to 12 degrees (if I remember the numbers right), and drops from there. This happens with every startup.

Interesting that you have 2 of those switches, on a 90hp there is only one for over-temp alarm.

Yep, I thought all the 3 cylinder inlines were set up the same, so it sounds like I am wrong about that.
I am not sure what tells the CDI the motor has warmed up on those 90S.
someone will need to dig into this farther and let us know.

I was just pointing out what you wrote, and that retarding the timing lowers RPM, so the timing after start up has to be advanced to get the higher idle than normal
BTDC is advanced, and ATDC is retarded (Before and After TDC)

Normal warmed up IDLE timing on my C40 is 7 ATDC
I Have no idea what the 90 idles at under warmed up conditions, but I would not think it would be 6ATDC during the high idle after a cold start

[holmen78]

Had to look it up. Fully retarded, or reversed like it says in the work shop manual should be 8 degrees ATDC on a 90hp. If it is not at 8 degrees after 1 minute it should be adjusted.

[muddfunk]

Advance the timing is what I wrote Could you send a picture of the switch that tells the CDI that the motor is warm? I am curious to see what it looks like.

To Robert Graham and mudfunk: Can you write here when you fix this problem and how you did it, I want to fix mine too.

Absolutely, I will post the results when it's fixed. Thanks a lot everyone.

[robert graham]

Advance the timing is what I wrote Could you send a picture of the switch that tells the CDI that the motor is warm? I am curious to see what it looks like.

To Robert Graham and mudfunk: Can you write here when you fix this problem and how you did it, I want to fix mine too.

When I cold start my motor It seems to start better with the fast idle lever cracked open just a bit....after it starts I leave the lever opened just enough for 1500 RPM's/ quicker warm up......the rest of the day the motor starts instantly with the start switch and no idle lever required.......I've never had your high idle issue so I don't know the solution to the issue....Hopefully Boscoe or Fairdeal will chime in with some real answers for you.....I'll be interested in their thoughts on this problem....

[99yam40]

Had to look it up. Fully retarded, or reversed like it says in the work shop manual should be 8 degrees ATDC on a 90hp. If it is not at 8 degrees after 1 minute it should be adjusted.

Back when I was having problems (2009)on my timing being retarded too much at idle warmed up(12-14 instead of 7

ATDC

) C40TLRX .
I checked with a light and found that

the timing is advanced to about 4 degrees BTDC at start up and warm up and then drops back to 7ATDC or what ever you have the retard stop screw adjusted to once it warmed up.

I ended up replacing my CDI and that fixed the problem with being too far retarded ,
so then I set the stops as manual said to and the pointers were at 7 ATDC mark for idle and 25BTDC mark for WOT the light showed that also.
and I had to readjust linkages for everything back to what was in service manual.
Previous owners had jacked it around trying to make it run too far retarded

I would think your12 BTDC for your 90 may be too far advanced for start up (Too much advance and the motor would be hard to spin fighting the pistons pushing down) and 6 ATDC would be too far retarded to get RPM up to motor running to warm the motor

Since I have not seen anything in specs on this we need someone with a good running 90 to do some testing and report back here.

Robert Graham or anyone else with a 90 do you have a timing light and a little time?
check to see what the timing light says while cranking the motor and then once it is started what is the timing during warm up.

matter of fact the OP needs to check his also and report back

[robert graham]

I don't have a timing light ....cracking open my idle lever for cold starts just seems to work the best for me....don't know if it's recommended by the book or other outboard experts I just don't know. As long as I pump the primer bulb just before cold starts, then she always has cranked up cold now for 20 years without fail or issue. About a 1 or 2 minute cold start warm-up period is a highly recommended routine that prolongs the life of the motor....