Mariner will only attain half throttle

[Af4408]

My '89 Mariner 40hp 2cyl starts perfectly, idles good and great hole shot, however after about a 1/2 mile running smooth and strong the engine bogs down and I can only attain half throttle, it still runs good but as soon as I try to throttle up it bogs down again and will run only at half throttle. If I turn it off wait about half an hour it runs perfect for a few minutes (5) then the same thing happens again. There's good fuel pressure, good water flow and it does not misfire. My question; does this sound like fuel or electrical? any help is appreciated. By the way nothing happens when I squeeze the bulb.
I did notice that the water out of the **** hole is always cold.

 

[henrye718]

Re: Mariner will only attain half throttle

It really sounds like the engine electronics are limiting it by going into some kind of prtection mode to slow the engine from damage due to it sensing something is wrong. However, I am not at all farmiliar with mercs so I have no idea what the feature would be called. Also look up "vapor lock" and check your wiring harness, perhaps a wire is becoming undone to expansion and contraction after the engine heats up.

 

[Af4408]

Re: Mariner will only attain half throttle

Thanks for the response, I finally took it in to my boat mechanic and the first thing he did was unscrew the gas cap. When he did this a swoshing sound occured and he told me to get a plastic gas tank. Apparently the bleeder port plugged up on my metal tank and that caused the low flow of fuel. The boat runs great now.