Help!!!

[Logic186]

I need help please!!! I am having problems with my 2001 Logic 186, when I am at full throttle or even 3/4 the power surges from 4K to 4.7K rpms. I have changed out the fuel pump, pumped out the gas and added new gas, had the carborators cleaned and put a water/fuel seperator on and it still does it. Anyone else have this problem or know of someone who has had it. I need help bad. My next step is to take the tank out and check it, I have already hooked the engine up to a 6 gallon tank and it ran in the 5500 rpm rang with no problems.
Thanks,
Danny

[Cincinnati]

What motor do you have?
Does it do it all the time or only occaisionally?
Is this in rough seas or flat water?
Did you run the test tank long enough to ensure that fixed the problem?
Does your separator filter have a bowl on the bottom - did you drain it to see if there is water in the fuel?
Is your motor trimmed down enough - is the prop ventilating?

[Logic186]

I have the 2002 Mercury 115 SW.

It does it all the time on the tank in my hull and I did check the W/F seperator and it had no water in it. It is happining in calm water, when I ran the test tank I ran a full 6 gals out of it and it ran fine.
And the motor does it at all time no matter where the motor is trim to.

[Cincinnati]

Hopefully the problem is a simple one. Assuming for a moment that all the gas in the hull's tank is good, then start with inspecting the fuel line. Start from the cowling and look to see if there are any kinks or possible kinking with the motor turned in either direction in the splash-well. Then inspect the primer bulb - does it get firm when pumped? I guess a kink in the fuel line that is sporadic could cause fuel starvation on a temporary basis and give rise to surging when the motor is getting enough fuel.

If all the above does not help, then check to see if your fuel vent is open and free of blockage (next to the gas cap). Lastly, you'll need to inspect the antisiphon valve, if equipped.

This exhausts my knowledge and ideas - I'm no mechanic. Report back with what you find.

[Logic186]

I will try all of those things, I am offshore at work right now, I will be at work for three weeks and then I will try it out.

Thanks again for all your help!

[Logic186]

I finally fixed the problem! A buddy of mine told me that he had the same problem on another boat and he was told to take the prop off and have it checked. I did and low and behold it fixed it, the prop was bent. I would have never thought it would be the prop. If anyone else is haveing this problem I would try the prop. $70.00 and its fixed. Thanks for all the suggestions guys!

[AstroDiver]

Now, I can't reason out why it ran good on the aux tank and not the onboard tank if it was a bad prop? Huh?

astro's right. And if prop that bad bent, you would see it on the motor. Boat should run the same no matter the fuel source. Make sure your radio works may need it?