Rodbolt wrote >>>>

[ttles714]

its a stupidly simple 2 speed 12V pump.
at key on the pump and injectors get 12V via the main relay.
the ECU controls the ground path.
at key on the resistor is bypassed.
at RPM above about 1200 the resistor is bypassed.
the resistor will drop pump operating voltage to about 9 volts below 1200 RPM to prevent running the pump in a stalled condition.

So what energizes the coil of the "main relay".. Is it the key switch being turned to the on position. ??

[greasyshaft]

Yellow is key on power.
From my understanding the Key switch powers on the ECU which then powers on the main relay.

[rodbolt17]

and once the main relay os ON any yellow/red wire will have 12V to ground.

[ttles714]

Power from ?? and thank you

Just trying to understand this a little better.... It is fixed thanks for your replies. It looks like the yellow gets 12 volt power from the key. As the relay is activated, power is connected to the red/yellow wire from the red hot wire. It is my understanding that the negative side of the pump is con*****ed by the CDI. Am I correct here or am I missing something ??

[rodbolt17]

yes the negative side of the pump(s) is con*****ed by the CDI.
some models use a fuel pump relay that is con*****ed by the ECU as well.

[ttles714]

Rodbolt ..Thanks for the education

Rodbolt...Thanks for taking the time to help me understand how it works.. goes a long way in fixing the problems... A short season here in Jersey... when something goes wrong waiting for a mechanic who is jammed up with work can be a long stretch,.... ( one of the reasons I purchased a spare engine in case of a major catastrophe).Your wealth of knowledge here on this forum is invaluable, and much appreciated. Can I at least send you a bottle of wine ??

Thanks ... ttles714 ( Tony)

[boscoe99]

In connection with a Yamaha what is a barometric sensor?

I am quite familiar with Yamaha stuff but have never heard that terminology.

Can you point me to a specific section of a Yamaha parts catalog where I can find that sensor by its name?

[ttles714]

spare outboard

My boat has twin ox66 250's. they are 14 years old. I think they are very good motors. BUT they are 14 years old. If I blow one or need parts during my relatively short boating season, I have another complete unit to install or salvage parts from. It was worth the cost of the extra (same ) motor so as not to ruin my boating summer. I like these motors and really have no desire to re-power, especially if I have no alternative but to do so in the middle of the summer. And I am not looking to spend 40 K $$ to do so. So for a few thousand I have an option and a little insurance. ( paid off for this weekend).
I guess it depends on how you look at it.

By the way .... I am not sure about that sensor !!! LOL !!

But thanks for your response very much.

[99yam40]

Boscoe You went back on your word and posted on a thread he did.
Shame on you

[boscoe99]

I know. So ashamed of myself. I am not worthy.

He will only leave if all of us will ignore him. I could not get the others to go along.

He will fit in so well at The Hull Truth that I can't imagine why he remains here with us dunces who don't know squat about Yamaha outboard motors.

[rodbolt17]

and whats funny, this idiot clown that will remain un named is to stupid to know that yes the OX66 motors did use a baro sensor.
however it is NOT used once the engine is running.
the MAP sensor on the OX66 simply locks in baro pressure for that key cycle.

it must be rough to be an idiot and not even know it,

and whats extra amusing is the un named idiot cant tell the difference between the various OX66 systems,HPDI systems or the 4 stroke EFI systems.

pay no attention to the un named idiot and the rest of us can try to talk you through it.