Re: which prop for a 1977 mercury1150 ???
A lot depends on how you load your boat and what you do. I have a 20' deep V that has a '79 115 and came with a 19P prop. When I tested the boat before buying it ran very well with the 19P at WOT of about 5800rpm and 40mph with two people and half tank of gas. Then after it was restored and I added 4 people, full gas, all my fishing gear, three batteries, 4 down riggers, extra 12lb balls, new merc 4stroke 9.9 pro-troller, all the other stuff, it wouldn't get to even 4600. I ended up with a 4 blade 15 pitch to get back up to 5500rpm and maybe low 30's mph. I only use my boat to salmon fish Lake Michigan and don't care much about speed cause its seldom I can run WOT anyway because of the waves. I also have a lot of slip because of the deep V and a lot of weight but the 4 blade helps with that and makes me feel like I have four wheel drive in following seas. I do also agree that a 19P might be a good place to start for your boat, but don't be upset if it isn't right. By the way my 19P is now my spare as someone already suggested. It will get me home in an emergency.