89 225hp Evinrude runs off?

[RoughFishAssassins]

Well I bought this a year ago and installed on our boat. in the warmer times of the year the motor starts fine and runs ok till headed to WOT, that's when it starts surging for a lack of better words. RPMs will be going fine then they will fall, never changing throttle position, then they will rev back up only to fall again. this happens like I said near WOT. now if this isn't weird enough, when it is cooler out, 40s, this problem isn't there, the motor runs like a champ. Can someone please help me out with this? All the electronics have been replaced, the carbs have been cleaned. The VRO is bypassed and running mix gas. We use the boat mostly in the warmer months that's why the problem is most common for us, but when we had it out later in the year and didn't have that problem, that's when I really started scratching my head. Pleas help.

 

[racerone]

Test run with a " known to be good " hose and tank.

 

[interalian]

And try squeezing the primer bulb when it's doing that. Could be a weak pump.

 

[ondarvr]

When you say "all of the electronics have been replaced", what exactly do you mean? it makes a difference.

 

[Faztbullet]

When it happens bump the key(choke) and see it it picks up RPM, if so fuel pressure related....

 

[boobie]

Try doing a cylinder drop test on it when it's acting up.

 

[RoughFishAssassins]

OK, I have done the primer squeeze, had no change, and also the key bump, well chocked the motor. As far as what electronics, new packs, plugs, and the main board, forgot what it was exactly.

​BUT... the real problem is that it isn't acting up in cold weather/ cooler water...WHY???

​I truly appreciate all the help, no one will work on my boat "legally", something about over powering....

 

[ondarvr]

Electronics tend to fail more often as they heat up, so it's possible in the summer it gets just hot enough to cause a periodic failure.

Is the change in RPM's sudden, like flipping a switch, or slower, moving up and then down? electrical is normally sudden, carburation is typical a slow change.

 

[RoughFishAssassins]

When the issue happens, it is almost like someone is taking the throttle and moving it up and down, not real fast just back and forth so to say, that is about the easiest way to explain it. After taking it out in the cooler weather and the issue not happening is what really has me perplexed.

 

[clanton]

You own a multimeter????????????

 

[boobie]

Change in temperature makes it act up is why I suggested the cylinder drop test. You may find which cyl/cyl 's are causing the problem.