5 HP Honda Outboard WOT Issue

Hello all, I am new to this forum and am hoping someone can help me. I have a 2006 Honda 5HP four stroke that has an issue only at full ( WOT) throttle. It starts on first pull, idles perfect and runs perfect until WOT. At that point it has a consistent bog-down. The motor never dies, just runs rough. If I back off a bit on the throttle, everything returns to normal.

I acquired this motor recently, so I do not have any history with it. This is what I have done so far,

Replaced carburetor- original needed replacing anyway due to stripped jet screw
Replaced fuel filter
Replaced Coil and spark plug
Verified good compression
Verified external fuel hose/bulb and fuel can is good by using both with another outboard with no issues.
Visually inspected fuel pump. I see no apparent issue, but this is the only major component that I have not replaced.

I am at a loss here...please help !

Thanks

Hi,
I don't know this model nor do I have any documentation on it. I changed a few pull starts on some 5's a while back and that is the extent of my experience with them.

Pretty much answering back since no one else has yet. You will likely get better info than mine but wanted to let you know that people are reading your post and that you're not being ignored.

The only things that I can think of that may be causing the symptoms you describe are;

Honda has been putting "engine protection" circuitry in their CDI units for many years. Overheat protection will "derate" or power down the engine to prevent damage.

Many engines will have a "rev limiter" as well to keep the engine from overspeeding in situations like having the prop come out of the water or falling off. It will cause the engine to sort of sputter and pop at high rpm if activated.

There may be a problem with the prop hub and the engine IS overspeeding.

I can't tell you if your outboard has overspeed protection but that's....kinda....sort of....what this sounds like to me.

I would check the prop hub for any movement. This is a small outboard so I wouldn't use a lever but if you activate the kill switch to prevent injury and put the outboard in gear, you should not be able to move the prop against the engine's compression by turning HARD with your hands. It shouldn't move at all.

Remember to slowly rotate the prop while selecting a gear to keep the clutch from binding up. Putting any outboard in gear while it's not running can bind the clutch if the prop isn't slowly rotated. If the clutch binds and you force it into gear, parts can bend or break. And don't worry about which direction or what gear. Simply rotating slowly and shifting will do the trick.

The only other thing that I can think of is that the valves could be out of adjustment. This might cause the engine to stumble at high rpm because it isn't "breathing" correctly. The valves need to be correctly adjusted for the engine to move air, fuel and exhaust in and out efficiently.
It's a very simple task that most people can accomplish with the correct tools (feeler gauges and, usually, a very tiny wrench) and the proper specifications.

I do hope that you were sold the correct replacement carburetor. A carb that isn't sized properly for a given application could cause this too.

Please keep us updated as to what you find. I hope someone else chimes in with some better suggestions.

Good luck.

Flywheel key ?

Will it pick up at full throttle if you pump the squeeze bulb? Then it is likely a weak fuel pump. How about the fuel filter, has it been replaced? Without looking it up, I'm assuming your model has a filter and/or fine screen. There is also a fine screen at the bottom of most fuel tank pickup tubes.