Over the winter I purchased a 280 Powerquest with a blown motor as a project. I purchased a mildly built 454 (505hp 54lb/ft torque) as a replacement. I dressed the engine with the stock efi system, added CMI headers, and a K&N flame arrestor. The engine was installed by a local boat mechanic. After a ton of other fixes, I finally got the boat to the lake. The problem, with the outdrive and trim tabs buried, the boat will barely come on plane. The engine has no power until it hits 3000 rpms (which takes forever) then takes off like a rocket ship. I am running a bravo 1 24p prop (same prop everyone with a 280 and a stock 454 use). I have even tried a friends 22p 4 blade. The holeshot was not improved at all. I had the ECM reprogramed for the new bore, cam, headers, flame arrestor, etc... I also had the injectors cleaned and flow tested. Anyone experienced a simular issue? I guess my next step is to have someone with a Merc scan tool check the efi system, and have the ECM tweaked. I can list the cam specs if needed.

Thanks.

If you are going to have the ECM reflashed, or go with a piggy-back unit like our CMD Marine unit, the first thing you will need to know is what the air/fuel ratio is currently. This will tell you (or your tuner) what changes need to be made.

The CMI's lend themselves to a fairly easy installation of wideband sensors. A local machine shop can probably handle this for you, or CMI will do it too. Once you have bungs in the tailpipes, then you can install a wideband monitoring device.

For use with our CMD Marine fuel tuner, we sell a single or dual channel wideband O2 controller and can couple either gauges or a LCD touchscreen display with logging capability. You can see the gauges and LCD at http://www.dynojetwb2.com.

did you run it on the dyno with the efi and the alleged new flash ? if not, what makes you think any part of it is correct ?