250 TXRR Help

Hi all! New to the site, and I could use some help. Before anyone says "try the search button", I did. I run a '93 250 TXRR. Recently there is a miss at idle, and it has a mind of it's own while running. Whether it's at the dock or under power, it will change change rpm without touching the throttle.
I've done the following yesterday:
replaced both fuel filiters
replaced plugs
checked coil packs for resistance and replaced one that showed none
ran motor with brand new fuel source

After all this it seems that the miss is actually more pronounced, and will actually stall the motor while at idle.

It seems to be electrical to me, and after close inspection of all the wiring I'm leaning towards the ECU.
Is there any kind of diagnosis that can be done to check the ECU before purchasing one?

Thanks in advance for any help, as it would be greatly appreciated...
Elf

I forgot to add that the fuel pump runs constantly while the key is on... is that normal? Thanks again...

[jb123]

have you tested the mechanical fuel pumps ?

The fuel pump is electrical, isn't it?... I'm pulling the carbs off to clean and re-install. I've heard that "...if it sneezes, it ain't breathin'...", so before I go the ECU route, I figured I'll clean the carbs first.

[jb123]

pretty sure on thse there is a electric one prior to the mechanical on the block. look on the port side , after filter.

Well, I've replaced the electric fuel pump, and the three mechanical fuel pumps... Carbs look brand new... Motor still runs like crap...
I give up... Anyone have an ECU in the NY area just to rule it out?
Thanks JB123 for the help.

I have the same motor, had a similar problem at idle and at mid throttle. I'd bet the idle is a fuel problem. I was stumped and took it to a mechanic. On mine, the low speed jets on several carbs had tiny blockages. They looked clean, but the mecanic used his exact sized probes to clean them and it idled fine from then on. At mid throttle, mine ran erattically, up and down rpms. I believe he replaced a small roller on the throttle cam - it was missing and allowed the engine to drift/surge with no throttle input. hope that helps.

Thanks! Tomorrows project...