The 153 in the Mercruiser form is a 120 HP engine. The 181 is 140 HP. I am building a .040 over 153 with a 181 crank for 175 ci. My head has 1.86" intakes and 1.60"exhaust, lumps, port work, milled .030". I had a custom cam ground by Erson. It has forged Ross flat tops at zero deck height. It will run a pair Zenith one barrels and a tube header. I expect to do better than the stock 181's 140 hp. I pick up the block from the machine shop tomorrow.
