I am new to boating. I have a 1970 evinrude 85hp starflite. I am not sure what the mechanic mixed the gas oil ratio at originally but it ran great and started with just a turn of a key. I used up my first tank of gas this weekend with seafoam and I mixed the next tank with seafoam and penzoil marine oil at 50:1. This seems to make it hard to start and it doesnt want to idle at low speed. I hope it is just a bit too rich. Any suggestions??