DF9.9 with new ECM for DF20 is surging, any ideas?

[onepyramid]

Just purchased a brand new DF9.9 with remote control, electric tilt, the works. Bought new ECM and flame arrestor for a DF20, installed it and it started right up. However, anything over idle speed and the engine surges constantly and will not settle down and run properly.

Any ideas?

[ElYako]

Sorry to hear that...I have the same surging at anything past idle on my new df20 so following. Changed plugs and cleaned hi/low filters, MAP sensor and renewed fuel, now stuck...

[onepyramid]

Not sure why, but mine was a prop issue. Stock motor had a 10" x 5" pitch prop on it. With the higher rpm available from the lack of restrictor plate and the new ecm, it was over reving causing the surge. At least that is my best guess. I had another motor with a 9.25" x 9" pitch prop. Swapped props and the surge went away and she runs like a champ.

[ElYako]

Glad yours is sorted...mine surges in neutral too though?