I'm planning to replace the omc outdrives on my 265 sedan bridge searay with the sei outdrives and conversion kits but i don't know what gear ratio i should order. How can i find out what i have and most important what would be best? I currently turn 15/15.5 al props and turn about 4400rpms. I have to run at 3800 rpms which gets me about 27mph or it starts plowing. I would like to get the rpms down but still get the 27mph. Is this possible?