Internet wisdom

[fairdeal]

I don't know much about outboard motors, but owning two older Yamaha 4 strokes, I am always interested in learning more - and thanks to the internet, every day brings new insights.

This site is very informative, but I also keep an eye on a couple of others.

A few days ago, on "another site" I learned that,
- regarding the 2007 Yamaha F150 -
"the ECU shuts the spark if the fuel rail pressure is too low "

This fact was confirmed by a second poster, who observed
"yeah but once you turn off the engine and turn it back on that should reset"

Now just today on that same site, I read the following:

"All of the yamaha 4.2 V6's use the same major components and ECU mapping. All the way from the vmax sho 200 up to the 300 offshore. The only difference in the units (outside controls gearing on the offshore unit) is the amount of throttle the ECU allows to be open. This is an electronic equivalent of putting too small of a carb or a throttle stop back in the carb days. For instance a 200 Vmax may only allow the throttle plate to be opened 20 percent where as the 300 will allow 100 percent opening. This trick was done to make the engine "feel" much bigger than it is listed at. In fact all of the engines are essentially 300hp engines that have the rains pulled back on them. Since the lower horsepower motors dont allow the throttle to open all the way they dont allow complete cylinder filling during the peak VE curve of the motor. This intern leads to a lower effective dynamic compression and means they are not as prone to detonating thus they do not require as high of an octane rating to make their listed horsepower. That being said they all run the same spark / fuel map and have the same cam shaft. Being high compression they are prone to some detonation. Running a lower octane will lead to a retarding of the spark map and slightly lower hp on all units but due to the throttle limiting the HP difference will be smaller on the units toward the lower end and will be greatest on the 300hp model. "

There's a lot of info there for me to digest;

I wonder if anyone here would be interested in breaking it down and clarifying?

Is this latest post as helpful and reliable as the prior information?

[boscoe99]

I don't know much about outboard motors, but owning two older Yamaha 4 strokes, I am always interested in learning more - and thanks to the internet, every day brings new insights.

This site is very informative, but I also keep an eye on a couple of others.

A few days ago, on "another site" I learned that,
- regarding the 2007 Yamaha F150 -
"the ECU shuts the spark if the fuel rail pressure is too low "

This fact was confirmed by a second poster, who observed
"yeah but once you turn off the engine and turn it back on that should reset"

There is no fuel pressure sensor on the F150. I don't know how the ECU could know what the status of the fuel pressure is.

Now just today on that same site, I read the following:

"All of the yamaha 4.2 V6's use the same major components and ECU mapping. All the way from the vmax sho 200 up to the 300 offshore. The only difference in the units (outside controls gearing on the offshore unit) is the amount of throttle the ECU allows to be open. This is an electronic equivalent of putting too small of a carb or a throttle stop back in the carb days. For instance a 200 Vmax may only allow the throttle plate to be opened 20 percent where as the 300 will allow 100 percent opening. This trick was done to make the engine "feel" much bigger than it is listed at. In fact all of the engines are essentially 300hp engines that have the rains pulled back on them. Since the lower horsepower motors dont allow the throttle to open all the way they dont allow complete cylinder filling during the peak VE curve of the motor. This intern leads to a lower effective dynamic compression and means they are not as prone to detonating thus they do not require as high of an octane rating to make their listed horsepower. That being said they all run the same spark / fuel map and have the same cam shaft. Being high compression they are prone to some detonation. Running a lower octane will lead to a retarding of the spark map and slightly lower hp on all units but due to the throttle limiting the HP difference will be smaller on the units toward the lower end and will be greatest on the 300hp model. "

There's a lot of info there for me to digest;

I wonder if anyone here would be interested in breaking it down and clarifying?

Is this latest post as helpful and reliable as the prior information?

The 4.2L SHO's are very similar. The difference amongst the three models is the the ECU. If the cowling graphics and the model identity plate are excluded that is.

The 4.2L Offshores are very similar. The difference amongst the three models is the the ECU. If the cowling graphics and the model identity plate are excluded that is.

The SHO's and the Offshores models differ quite a bit. Only real similarity is the block and heads. Many many more differences than similarities.

My gut feel is that what you read on the internet is basically garbage. The internet is great for spreading untruths far and wide. And often. Because it is in print folks believe it to be true.

Where did you read this stuff?

[ausnoelm]

Hhmmm, so all are 300HP? But, the throttle is not allowed to open by the ECU, interesting concept, not exactly sure where you got your information from, perhaps Rodbolt can "myth bust" this for you?

[rodbolt17]

I can definatly bust the F150 myth.
the F150 cannot and does not monitor ANY fuel pressures.
that was easy.
on the 4.2L yes the ECU controls the throttle based on lever or accelerator position and ECU mapping.
it also controls ign timing camshaft timing(intake cam) and fuel injector on time.
but you read it on the net so it must be true.

to many backyardigans.