I have a 16' Challenger boat, made in Montclair, CA in the early 70's. I am the original owner, boat has a 1971 135 HP Merc, it still runs but is very tired. About 5 years ago, I lost reverse, so I had the lower unit gone thru. EVERYTHING was gone, so everything was replaced except the cases. Had a nose cone installed, so now the lower unit is virtually new but the power head is very weak. Have not done a compression test, but after 30 years, things have got to be bad. It starts and idles smoothly, but just really down on power. Question is, should I be looking at a new/newer motor or should I consider having this one rebuilt. New 150's and 175's seem to be in the 8 to 10 thousand range, and I don't have a clue what kind of money it would take to freshen this one up or even if its worth putting money into. If anybody out there has any idea's, I'm open for your opinions or help!! Thanks again!