2007 90HP Yamaha 2 stroke Idle Problems

[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....

[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]

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....

[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.

[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.

[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]

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]

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]

The CDI does not retard the timing to make the idle RPM higher, it advances the timing.
If this 90 is like my C40 ,after the motor warms up ,one of the switches on the head tells the CDI it is time to drop back to its normal idle timing (which is ATDC, retarded) and the RPM drops to normal.

But I agree, use a timing light to watch what the timing is doing while motor is running in the driveway on muffs or sitting in the water at the dock.
turn the motor off after it warmed up, and start it back up right away to see what it does.
then turn back off and wait for some time and start it up again
see what it does

pull and check the stat to make sure it is not stuck open and also test it in a pot of water as you heat it up to see if it operates according to specs.
monitor the water temp and watch when the stat starts to open and when it gets to full open

you can also test the switches like that , but monitor the switch action with an ohm meter

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.

[99yam40]

O.K., I stop to fish for an hour, then when I start my motor it doesn't run at high idle at all.....if it ran at 1500 RPM's on it's own, then I'd say that was not normal or desirable for my motor......what I'm supposed to do, sit there and weight for my motor to idle back down so I can put it in gear?...you've got some kinda problem...

but why do you open the fast Idle lever when you start it cold?
it should idle up all by itself and then go back to normal idle without your help, that is what the prime start is designed to do.

If your does not do that, then you may have a problem also.
it is not that he may not have a problem, but comparing his to yours when you have to raise the idle for cold start and he does not may mean more that one has a problem.
if he is boating in cold water it would make a difference.
My C40 always starts at high Idle without any use of the fast Idle lever, even warm, but if it has been running within the last few minutes of the restart it only lasts for a few seconds, if it has been an hour the it stays up for a little longer, but I am in warm water here on the Tx coast and I have no idea where he is located

[robert graham]

O.K., I stop to fish for an hour, then when I start my motor it doesn't run at high idle at all.....if it ran at 1500 RPM's on it's own, then I'd say that was not normal or desirable for my motor......what I'm supposed to do, sit there and weight for my motor to idle back down so I can put it in gear?...you've got some kinda problem...

[99yam40]

Ok, one more try. Take a timing light and watch the timing at start up. The CDI advances the timing to about 10-12 degrees BTDC at startup if I remember the numbers right. The CDI retards the timing during the 40-45sec period after startup. After the 40-45 seconds the final timing should be 6 degrees ATDC if adjusted right. The change in timing makes your motor to rev up and stay running when cold. The CDI does not know if your motor is warm or not, that’s why it does it every time you fire it up no matter if you just run 20miles and had it shut down for a minute. The startup “sequence” on a warm motor is a little different because the prime start valve will be shut off on a warm motor. The only temperature measuring device is the thermo switch for your over temp alarm, an on/off switch. The thermo switch is not even wired through the CDI, the pink wire goes from the switch directly to your remote control alarm buzzer.

The CDI does not retard the timing to make the idle RPM higher, it advances the timing.
If this 90 is like my C40 ,after the motor warms up ,one of the switches on the head tells the CDI it is time to drop back to its normal idle timing (which is ATDC, retarded) and the RPM drops to normal.

But I agree, use a timing light to watch what the timing is doing while motor is running in the driveway on muffs or sitting in the water at the dock.
turn the motor off after it warmed up, and start it back up right away to see what it does.
then turn back off and wait for some time and start it up again
see what it does

pull and check the stat to make sure it is not stuck open and also test it in a pot of water as you heat it up to see if it operates according to specs.
monitor the water temp and watch when the stat starts to open and when it gets to full open

you can also test the switches like that , but monitor the switch action with an ohm meter

[99yam40]

^^^^, if so, perhaps the temp switch should be inspected.

If it's sending wrong info to the ECU, telling it the engines COLD, when it isn't, That would likely raise the idle, keep it there (thinking it's NOT warming up-when it IS)..

Just a thought..

.

my c40 has 2 switches on it ,one for over temp and the other for motor warmed up,
I would think all of the 3 cylinder motor would be similar.

[holmen78]

Ok, one more try. Take a timing light and watch the timing at start up. The CDI advances the timing to about 10-12 degrees BTDC at startup if I remember the numbers right. The CDI retards the timing during the 40-45sec period after startup. After the 40-45 seconds the final timing should be 6 degrees ATDC if adjusted right. The change in timing makes your motor to rev up and stay running when cold. The CDI does not know if your motor is warm or not, that’s why it does it every time you fire it up no matter if you just run 20miles and had it shut down for a minute. The startup “sequence” on a warm motor is a little different because the prime start valve will be shut off on a warm motor. The only temperature measuring device is the thermo switch for your over temp alarm, an on/off switch. The thermo switch is not even wired through the CDI, the pink wire goes from the switch directly to your remote control alarm buzzer.

[TownsendsFJR1300]

since you say you idle your motor at 1500 for a minute or more, and his takes 45 seconds to drop down to normal idle , how can you say his has a problem?

I believe the CDi changes the timing at start up and depends on a temp switch to tell it when the motor is warmed up to go to normal timing

^^^^, if so, perhaps the temp switch should be inspected.

If it's sending wrong info to the ECU, telling it the engines COLD, when it isn't, That would likely raise the idle, keep it there (thinking it's NOT warming up-when it IS)..

Just a thought..

.