More help with 1974 20 hp Merc..Please

Ok, The dealer got the prop in and I went and picked it up and installed it on the motor. I put the boat into the river and the motor ran fine, like a dream actually. I went up river about 4 miles and I stopped and let the engine idle in neutral. Water was coming out the pee hole and every thing seemed fine. I kicked the motor back into gear and it started to stutter. The it stall out. When I got it started again it would barely stay running. Then it died. It was smoking just a little so I let it cool off while I trolled back with my TM. After about 15 minutes, I tried to start it again and it started but I could not get any speed out of it at all. WOT was just spittin and a sputterin. Just a half an hour ago it was running with the big boys and now I am limping down the Mississippi River hoping to make it back to the dock. It stopped running just in front of the dock. The cowl was very warm, and some smoke was coming out from it. I loaded it up and brought her home. Here is the deal. I am into this motor for about $600 and I do not know what is wrong with it. Do I take it into the shop and have them look it over and shell out another $100 ? The other thing is, the old prop that came off was a 7 pitch and that is what I ordered. But after looking at the box, they gave me a 9 pitch. Could the have anything to do with it? I am stumped. I took the cowl off when I got home and everything looks good and it does not smell burnt. Any help would be greatly appreciated. I just want to fish!

Tim

If it's a 2 blade prop, I'm pretty sure 9 pitch is what came on it from the factory. I have seen a lot of used 7 pitch props for that motor for sale on the UK ebay though so maybe 7 pitch was popular their. Either way, I don't think that is what's causing your problem. The only difference a pitch change should make is a higher or lower rpm at full throttle. Did you happen to check to see if it was pumping water when you came back to the dock? Have you checked to see if you have spark on both cylinders?

Its a 3 blade and the box states that it is for my make and model. Just wondering why it would be fine going down and then sputter out on me. I guess it will need to go to the shop for a look see.