I have a 1988 volvo penta aq131d. Bought last year ran great all summer. This summer I gave it a tune up, plugs, points, condensor, cap, a new coil fuel pump and filter, oil change. Well after fixing water plug leaking out of exhast manifold ( Did'nt drain it opps) it started and ran fine but after a short while I seem to lose power and it seems to want to shut down. I slip it out of gear and she idles fine. Sometimes after running slow at 1500prms 10 mins or more I can hit it and she flys. But when I cut her down she starts choking again. It was choking at full throttle back to the dock then she opened up and took off as if nothing was wrong. At the shop the mech said she would not idle unless he gave it gas. I had that happen a few times on the water as well which is why I am confused. Mech said intermitent problems have to be fixed when they are completly dead. What to do ? Im lost on this one.