Ported 260 stumbles on take off

[local103racing]

Hi I have a ported 260 merc my question is when take off out of the hole it will stumble then eventually catch and plain off. If I trim my motor all the way down she takes off fine any help would be great it has a new fuel pump injectors have been flowed and tested new everything in this motor runs great on plain and only happens on take off if motor is trimmed up a little

 

[tomoad]

R u running a thru hub or over hub type prop. Or 4 blade prop?

 

[XXXR2001]

When you trim up to take off could the fuel line be getting kinked? If it's stumbling, it's probably lean. These motors use alot more fuel to take off than when on plane so a small blockage could have a bigger impact at that point. Otherwise, has your ecu potentiometer setting changed? Definitely something to chck.

 

[local103racing]

I'm running a 4 blade trophy stock prop on a 20 inch ros mid with a drag tuner and a 187 sportsmaste

 

[local103racing]

When you trim up to take off could the fuel line be getting kinked? If it's stumbling, it's probably lean. These motors use alot more fuel to take off than when on plane so a small blockage could have a bigger impact at that point. Otherwise, has your ecu potentiometer setting changed? Definitely something to chck.

That's a good question I will look at that for sure

 

[tomoad]

Put you a chopper or et prop and go try again. I bet there will be no hesitation. My 280 does the same thing at the hit of throttle for a second or two with a trophy on.

 

[local103racing]

Thanks so much for all the advice I thought it could have been plugs bad coil clogged up breather fittings clogged up Ecu tube but all it was is I had the stock trophy on it I changed it back to my 28 big ear chopper and she runs perfect now only thing I can think it did was restrict the exhaust and it loaded up way to much but it's all set now

 

[tomoad]

Not a problem. Glad we caught before you went to chasing a ghost. I know I almost did.

 

[chad202]

you may have to advance your idle timing also.

 

[local103racing]

Chad why do I need to advance my timing it seems to run great now with my 28 chopper my only question is why does my 25 trophy make it bog only on takeoff but will jump out of the hole if it's tilted all the way down I can't figure that one out

 

[local103racing]

Not a problem. Glad we caught before you went to chasing a ghost. I know I almost did.[/

what did you use as a power prop I still have no clue why that trophy won't run right

 

[whipper]

Advancing the idle timing allows for a longer duration of flame contact with the piston. So leaner less bog than retarded for hole shot. You just dont want to advance to far because that will create to much heat. Depending on the acu you can advance timming then add more fuel for right after take off to complement for the added burn duration and make more power or something like that. Having an EGT hooked up makes this proses way easier. Some times if your running a little to safe rich or retarded the bog can be form loading up with the more restrictive exhaust hubs. Once she blows buy after take off your good to go. Im not sure if I explained that right but i had a similar situation and did this but im no mechanic so I may have missed something hear just so ya know. Checking your own timming is easy if you have a good TDC gage. I use JaySmiths top dead centre one works great to get dead nuts. These guys with 260,s can tell ya were they run there timing with success and what oil ratio. Its worth checking so ya know were your at any way. It can make a difference even out buy one degree. When ya do it yourself your very careful and accurate with your baby.

 

[tomoad]

I run Mercury ET's. & Choppers cut to the "Knob Cut" from Todd at Hydromotive. They work very good. Either in a 26 mostly because I do a lot of bass fishing. If I know I'm making a long run I'll throw a 28 on merely to help save gas.

 

[local103racing]

Thanks guys all real good info I appreciate all the feedback it has helped me a lot