An old thread helped me find the spark plug gap (30-40). I replaced a 13” 17p 3 blade prop that was getting 5200rpm top. The new 12.25” 19p 4-blade yielded only 4800rpm so settled on 12.75” 17p 4 blade to get 5200 again. So…..what is the correct max rpm for this engine? Runs great but I...