My former mechanic replaced my 1979 Mercruiser 228 (305 GM, 4bbl) with a 305cu in Grooms Marine rebuild. The Mercruiser 228 with an Alpha 1 Drive and 14x19 stainless prop on my 20' Mark Twain did the following:
2600rpm = 26MPH
3000rpm = 30MPH
4400rmp = 48MPH WOT Trimmed
The Grooms engine with...
