A question for the experts... Blew the 5.0 at the end of last season and replaced it with a 5.7. The 5.0 had TBI and was in a 1998 deck boat. I replaced the long block with a fresh 5.7 and installed all the 5.0 electronics with exception to the knock sensor which I installed a 5.7 knock. Now, the engine will run but cannot hold a steady idle. The timing light shows the mark moving about 15 degrees each direction. The injectors are for a high output 5.7 so should be OK. Dealer is now telling me that I need a 5.7 ECU at a cost of $1100. I was under the impression that the 5.0 ECU would work fine on the 5.7 and have a hard time believing that a 5.7 ECU will solve the problem. Not to mention $1100!!! Is there that big a difference between a 5.0 and 5.7 ECU, is there a big difference between an automotive and marine application? Summer is coming quick so any input would be greatly appreciated!