FYI This is a remanufactured long block from Rapido Marine with about 12 hours on it. I did a compression check and all cylinders are at 150
Please don't let this deter you from trying a vacuum test as at this time, it honestly seems important to know what the internal engine components are doing even though it's a new engine. We've all read enough forum posts to know while somewhat rare, new engines have been known to get internally damaged in sort time frames.
Hope it's not your case but you need to know for sure before to much more time passes on.
The scan tool is very nice to have and helps solve many issues as long as you know how to read the live data parameters for your engine model but honestly having a code on the older MEFI system doesn't necessarily always put it into power reduction mode and yours being a 1996, power reduction should have been removed as quoted below from some past service notes. But if one of the sensors parameters are on the high or low end of the scale but not out of "range" the engine will not perform exactly right while not throwing a fault code either. That's where the scan tool comes in handy reading the live data at WOT.
I don't believe your at the point of really needing to buy the scan tool just yet if money is really tight...But if you can afford it and plan to always work on the boat, go for it and or keep an eye on EBay as the older version scan tool tends to pop up at a good deal from time to time.
1996 model year notes:
5.7L EFI ? Alpha, Bravo 1, 2 or 3 (220 pshp/4200-4600 rpm). VST fuel system. 2 bbl intake manifold.
5.7 LX EFI Gen + ? Alpha, Bravo 1, 2 or 3 (280 pshp/4400-4800 rpm). VST fuel system.
Looks like you may have went up in power between the two engines by 60 HP. By chance, what's the gear ratio you currently have and prop size? And highest recorded engine RPM with both the new and old engine?
https://www.seilermarine.com/info/mercruiser-drive-ratio-chart.php
http://www.sterndrivereplacement.co...r/alpha-one-gen-1/complete-sei-106/gear-chart
? All 1996 models use the MEFI 2 ECM case, but are loaded with MEFI 1 (GM 93) software. MEFI 2 cases can be identified as having long mounting bolts, instead of the short bolts used on MEFI 1 cases. Power reduction mode has been disabled on all 1996 models. If it is a MEFI 2 case, it does not have power reduction, regardless of the software loaded inside.
