89 225 Excel bogs on acceleration

[BQUICK]

Have to nail it to plane off. rpms slowly rise. Similar to a boat with too much prop pitch. Once on plane it runs great.

I'm thinking computer is retarding timing....maybe knock sensor malfunction or it is picking up something that it thinks is knock?

I've run into other cases of bogging that was due to lean/clogged carbs as evidenced by hitting choke and motor picks right up on acceleration. This is opposite....doesn't want choke. It's either too rich or retarded.

[99yam40]

you thought about putting a timing light on it to see??

[BQUICK]

Yeah, right....I'll go out at dusk and shine a timing light on it with the boat trying to plane off at full throttle

[pstephens46]

Somebody explain how a carbed motor interacts with a knock sensor please....

[rodbolt17]

that is easy. the carbs do not interact with the knock sensor.

[pstephens46]

that is easy. the carbs do not interact with the knock sensor.

I was surprised to read a 89 carbed model had a knock sensor. Under the impression you needed control of
fuel and timing to control detonation.

sorry for the hijack....

[BQUICK]

It has a throttle position sensor so in a way the carb interacts...just doesn't change mixure. A Yamaha tech bulletin says to ground the knock sensor and re-test....I'll try that next time I get it out on the water.

[99yam40]

If you have the boat on a trailer, just back into the water and hit the throttle while checking timing.

or tie it to the dock. Just make sure it is tied up good and get someone to help operate the motor or timing light

but then there is the test wheel that might be found