Slower with x642 than x640?

[jamespl]

Ok so I've been running an x640 with good results so I thought I would go with an x642 for a bit of extra speed but the boat seems to take longer to get up on plane and top speed is crap. Am I missing something here? I figured it's the same prop as the x640 just bigger so no outboard adjustment should be needed is that right?
I'm not sure if it's a flex problem as sometimes it planes better than others, will check that out first.

[dana]

Sometimes going bigger means the motor isn't able to get up to the same rpm, and will actually go slower. We need more info about your boat

[jamespl]

Ok. Stock motor, turnigy 120a esc set to 15deg timing using 5000mah 40c turnigy 2x2s. You could be right although as I sent my first post from pond side I didn't realise the motor had gotten a little wet due to a bit of a dunk! Do you think that could have been the prob? I have taken all the flex out regreased and adjusted the outboard up a little more.

[dana]

Stock is 1800kv?

[dana]

Ok so I would prolly get away from that prop and try something else. Those x6 props run better on lower kv motors. Jmo but maybe search threads to see what else is being used. Refer to stock esc to get correct timing. Water won't hurt the motor

[jamespl]

Yes that's right. I would imagine that motor should spin an x642 cos the 1500kv miss geico motor does it just fine.
I posted the bit about the mg motor before I seen your other post. Will give the x640 another try.

[dana]

Yes but there is a good difference in the amount of torque those 2 motors put out...

[jamespl]

Had a bit of a play and the flex must have not been catching properly. It's running the x642 without any probs now.