i have that 1977 merc 850 original motor on a 1977 glastron t166xl sportster trihull i bought last week.i want to express my thanks to all that responded to my questions.i utilized the info you all helped me with as well as my own mechcanical background and brought the 850 back to life.all is well and i have no doubt she will serve me and my family for many more years. again, thank you all. SINCERLY,travis in illinois soon to be back in michigan waters.