Merc 260 and the fuel setting number

[K-Dawg]

OK. I just bought myself a Mercury racing DDT by OTC. I have a a-48 BOX. Figured if I was gonna own a 260 I would need one of these to change the fuel setting. In 95 degree 80% humidity weather where is a good base line number to set it at to start 101, 99?

[Michael J Giesler]

first thing is do you have egts each motor is a little different props make a differnce to 100 should be a good setting to start from and go down from there a-48 is a good curve i'm no expert but some will chime in and help out also:thumbsup:

[pirogue]

Randy, watch the plugs and rpms. if your leaning and rpms stop increasing go back up one number. I'm not familiar with an a48 and 39lbs. You may also want to include what yr motor, stock or not, head cc's, prop and rpm. I would think your real safe at 100 and can go a little leaner not sure though. Make sure set up is thoroughly looked over and fuel system is tidy.

[patchesII]

I agree with what Craig said. Start out at 100 and your just gonna have to read your plugs. Each boat, motor, prop is gonna be a little different. I think you'll probably end up between 97 and 99 but DON'T start there. You''ll have to go up a few numbers in the wintertime but thats the beauty of having a DDT. It's quick and easy to do. Good luck with the DDT, I tried to buy it from Craig but ya'll had already started ya'lls deal. Once you get that ecu adjusted you need to sell it to me:). I can adjust mine without one but a DDT would be easier

[Jay Smith]

I agree with all . @ 100 your safe at high ambient temps and high humidity levels. The colder the air gets the more fuel the motor will demand to be safe. Also always remember that there is allot of movement between the numbers ( such as a high 100 to a low 100 )



"Be who you are and say what you feel....
Because those that matter...
don't mind...
And those that mind... don't , Won't or will EVER matter
matter."

Jay

[K-Dawg]

I thought it would only change ever other number, odd numbers at that? Like 101-99-97, etc.... Motor has june of 91 or 92 stamped on block. Was sold to me as fresh and stock. Has 150 PSI after being warmed up and then checked. Running a 26 et cut chopper at 7400 rpm. Still cant get it to turn up. Figured I need a DDT to for one of these motors. I have been fly'in blind so to speak as far as the fuel setting goes. To diagnose my problem and get this this running right I think a DDT is a must.

[Jay Smith]

If DDT digital boxes reads in odd it will change in next higher or lower odd number ....


BTW : What you set your box at has EVERYTHING to do with the air ( your ambient weather conditions ) , engines mods, and boat load..Play it safe shoot for the rich side.

My .02



"Be who you are and say what you feel....
Because those that matter...
don't mind...
And those that mind... don't , Won't or will EVER matter
matter."

Jay

[graynester]

a digital box only reeds in odd #s period no options.

set it at 103 to just go boatiing, running around and running top end with a big wheel makes the motor last.

99 is what they come from the factory and seems to be as lean as u want it and would be where to set it for the 1/4 mile.

but yes get a pyro gauge 1150 degrees is safe, and feul presure gauge also and pay attention.

B

[Michael J Giesler]

my question is when is it to hot 1300 deg or 1250 deg 1200 when does pistons start to fry:thumbsup:

[pirogue]

7400 with a 26 sounds on the low side, make sure motor is not buried and watch for blow outs, how much set back are you running? what kind of lower unit are you running and what height to do you think it is. 92' is old may want to get injectors checked out. Setup will mean alot, much more than tweaking ecu. BTW your ecu doesn't know your reading every other number so you can make an assumption where the even numbers are while watching ddt.

[K-Dawg]

Set up is good. A Sporty with a allison cut skeg on 14 inches of setback. Prop shaft 1/8th of an inch below the pad. Had the injectors cleaned at brucatos a few months ago. I am stumped. How do you check and change the fuel settings using the ddt?

[pirogue]

I think with 14" of setback it's too low. Turn key switch on and press 1, 4, 1, and 1 again if I remember right, then remove the plastic plug behind ecu and adjust. I will be up between noon and 6pm tomorrow you can call me if you want.

[RBT]

I have a OTC to sell for 400 bucks

The ECU reads air temp, it cannot read altitiude or humidity.
Load will effect fuel burn as much as anything. So if you get it on the edge and add weight you will increase your chances of a burn down. Props are the same. Do not trust EGT's, they are a ref point only and unless they are digital, totally useless if analog.
Also lean is NOT mean, you need fuel to make power. If the motor is steady state cruise, you want it just the lean side of four stroking.

[Jay Smith]

I agree with RBT. The motor needs fuel to make power , I have won World and High Points titles at 1100 degrees and NEVER burned pistons, EVER !!!



"Be who you are and say what you feel....
Because those that matter...
don't mind...
And those that mind... don't , Won't or will EVER
matter."

Jay

[chad202]

I've ran as low as 97 in the heat of the summer and as high as 103 in the winter. But this was after I installed dual pyro and performed plug readings to prove that 1175-1190 was where the motor ran best and plugs looked perfect. I wouldn't used a ddt, just made mental notes of the screw position. Before teh pyros, I just had it set at 101 and forgot about it.

[K-Dawg]

Well, if I read it right its set at 99. Guess the missing rpm is elsewhere