centerline
Regular Contributor
I bought a used boat... since then Ive been having some WOT running issues with the engine not coming up to rpm under load, and so did the previous owner, who bought it from an estate without any background information on it other than it was "supposed" to run great...
what I know for sure is, its a stock 1987 5.7, all original. NOT a vortec.
distributor is the original prestolite IBM-7013C with an electronlc pickup module in it. the flyweights seem to be free and snappy
after the initial (and disappointing) trial runs, I have pumped the fuel tank dry, flushed it, and pumped it out again to get all the old gas out, and then refilled it with ethanol free gas... and I checked the initial timing (6BTDC), the engine starts easy and runs fine, but it had no power... so I kept looking for problems and found a couple more of them.
the secondaries in the carb were stuck closed, but a bit of WD40 and working them and they freed up nicely... and then I pulled the exhaust elbows and found one of the flappers in the exhaust was stuck closed.... so I replaced the flappers, manifolds and riser elbows with all new parts and installed iridium spark plugs.
then back to the lake.... we idled out past the slow buoys, and then slowly opened the throttle... it seemed to run great. it climbed on plane much quicker and easier and i could now hear the secondaries open.... the boat, which on previous trips would only make 14mph was now quickly up to 20mph and climbing.... but at 22mph i felt a slight loss of power, and we dropped back to 20mph. then within 45 seconds another loss of power which took us down to 16mph..... so I stopped the boat and the engine was misfiring. this all happened within about 3 minutes of when I opened the throttle.... the engine started easy and sounded good except for the misfire.
so we limped to an anchorage and let the engine cool down, then pulled the spark plugs.
#2 and #8 cylinders had the spark plugs melted down, no tips, no electrodes, just the threaded portion and the white ceramic left.... all the others looked fine but with yellow on them rather than the normal shades of brown, black, or gray.... maybe due to the ethanol free gas?
when we got the boat back home, I checked compression... 145-150 on all cylinders except #2@ 0psi and #8@ 75psi.... after the disassembly I found the intake valves on both cylinders were leaking badly, but the exhaust seemed to be fine.... the intake valve on cylinder #8 was badly dished and the stem was almost 3/8 of an inch higher than the rest of them...
I dont know what led to the melt down, but I want to check the maximum advance timing to see what the distributor is doing at the higher rpm...
I have searched for hours on the internet looking for a torque curve chart for a 350 marine engine without success... but there is a lot of gossip on different forums claiming a wide range of numbers and what rpm these numbers are supposed to be seen at, but there is nothing that shows any commonality.... AND, a lot of the forums have some smartass saying check the manufacture specs and set it to that....yep, thats such an obvious solution but it seems no one can find any "manufacture torque curve specs" for the 5.7/350 engines. and neither can I... what is so top secret about these charts?...
can someone share some good proven Total Advance Timing numbers for a 5.7 MARINE engine with me, and at what rpm should the timing be "all in"?
thanks for any help...
what I know for sure is, its a stock 1987 5.7, all original. NOT a vortec.
distributor is the original prestolite IBM-7013C with an electronlc pickup module in it. the flyweights seem to be free and snappy
after the initial (and disappointing) trial runs, I have pumped the fuel tank dry, flushed it, and pumped it out again to get all the old gas out, and then refilled it with ethanol free gas... and I checked the initial timing (6BTDC), the engine starts easy and runs fine, but it had no power... so I kept looking for problems and found a couple more of them.
the secondaries in the carb were stuck closed, but a bit of WD40 and working them and they freed up nicely... and then I pulled the exhaust elbows and found one of the flappers in the exhaust was stuck closed.... so I replaced the flappers, manifolds and riser elbows with all new parts and installed iridium spark plugs.
then back to the lake.... we idled out past the slow buoys, and then slowly opened the throttle... it seemed to run great. it climbed on plane much quicker and easier and i could now hear the secondaries open.... the boat, which on previous trips would only make 14mph was now quickly up to 20mph and climbing.... but at 22mph i felt a slight loss of power, and we dropped back to 20mph. then within 45 seconds another loss of power which took us down to 16mph..... so I stopped the boat and the engine was misfiring. this all happened within about 3 minutes of when I opened the throttle.... the engine started easy and sounded good except for the misfire.
so we limped to an anchorage and let the engine cool down, then pulled the spark plugs.
#2 and #8 cylinders had the spark plugs melted down, no tips, no electrodes, just the threaded portion and the white ceramic left.... all the others looked fine but with yellow on them rather than the normal shades of brown, black, or gray.... maybe due to the ethanol free gas?
when we got the boat back home, I checked compression... 145-150 on all cylinders except #2@ 0psi and #8@ 75psi.... after the disassembly I found the intake valves on both cylinders were leaking badly, but the exhaust seemed to be fine.... the intake valve on cylinder #8 was badly dished and the stem was almost 3/8 of an inch higher than the rest of them...
I dont know what led to the melt down, but I want to check the maximum advance timing to see what the distributor is doing at the higher rpm...
I have searched for hours on the internet looking for a torque curve chart for a 350 marine engine without success... but there is a lot of gossip on different forums claiming a wide range of numbers and what rpm these numbers are supposed to be seen at, but there is nothing that shows any commonality.... AND, a lot of the forums have some smartass saying check the manufacture specs and set it to that....yep, thats such an obvious solution but it seems no one can find any "manufacture torque curve specs" for the 5.7/350 engines. and neither can I... what is so top secret about these charts?...
can someone share some good proven Total Advance Timing numbers for a 5.7 MARINE engine with me, and at what rpm should the timing be "all in"?
thanks for any help...
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