more '80 mercury 80 issues

1980 mercury 80hp inline 4 spinning quicksilver aluminum 17p on 18' glassmaster


Took the boat to lake anna today with a few friends. it ran great from about 10 am to 4 or so in the afternoon, except for the usual stalling when shifting. at about 4 or so i started noticing hesitation when throttling up. told my friend on the kneeboard to get back in the boat so we could get back and check the motor out. shut the engine off, he climbed in. got ready to head back, it wouldn't start. it would turn over, occasionally the engine would fire once and the bendix would spin back down. . tried various combinations of choke, high idle level, etc. tried it with both tanks and 1 gal reserve tank. noticed some fuel dripping out of the side of the engine, but wasn't coming from the fuel pump or lines. I had just rebuild the carburetors last weekend and set new floats and needles etc and i couldn't see any gas coming from carb throats. compression is 120psi across the board. got towed in by a friend, when we got back the campground i tried starting the engine with full fast idle but no choke and it started, but it would die when the throttle lever was returned to idle.
this engine always run great in the drive but acts up after 4 or 5 hours of running. been doing this for over a year despite all the hours and time ive put into it...so any ideas?
my dad suggested vapor lock in the float chamber could be messing with needles
its beyond me how it could run so good for four hours then not.

Re: more '80 mercury 80 issues

anyone?

Re: more '80 mercury 80 issues

Do you think the motor is overheating? You might run it for a while and see if it gets progressively hotter. I guess it is posible that the ignition components fail at high temperature. If you cannot isolate it, you might change the waterpump impeller and see if it improves. If it has been more than 2-3 years, it is likely due.

Re: more '80 mercury 80 issues

That was first in my mind too, put my hand all over powerhead as soon as motor died, I could hold my hand on powerhead for a long time, powerhead wasn't hot at all. Cooling water was warm to the touch but not hot. I wasn't running her that hard, mostly about 2,000 rpm wth the occaisonal few minute near wot. she pumps a whole lot of water and impeller and seals were changed 2 years ago. i'm thinking its a fuel problem because of the leaking fuel, but i don't see how it could go from running great for four + hours, then progressively worse then not at all.

Re: more '80 mercury 80 issues

any other ideas guys?
forgot to mention this in previous posts. this is how i finally got it to start about 20 minutes later. I applyed full fast idle lever, turned the key WITHOUT choking it. it fired and sputtered and stuttered at low rpm for a few seconds, then ran up to normal fast idle speed. still wouldn't idle when i pulled the fast idle lever back.
could the needles possible be sticking? i just put new needles, seats, and floats in a week or two ago and set them per clymer manual.