I have a '96 Chaparral 180LE Bowrider with a Mercruiser 4.3 LX Gen+ with Alpha I outdrive.
I have an engine stumble after running at high speed cruise or WOT for several minutes, otherwise it runs great (it even runs great for several minutes at high speed cruise and WOT, until the stumble happens). The engine stumble is a significant RPM drop / loss of power. If you back of the throttle and "nurse it" you can keep the engine running, then continue on at a comfortable cruise speed. The one time the engine died from the stumble, I went to neutral, let the boat stop and turned the key off. The engine started again with a bump of the key, idled and ran fine at a slow/medium cruise all the way home.
I bought the boat 3 summers ago as a non-running boat. I got the boat running after replacing the electric fuel pump, overhauled the carb, set the timing and replaced the plugs and wires, and it has run like a top the last 2 seasons. The previous owner had done some ignition work trying to get it running and now I am trying to work with / around (or replace) some of the previous owners repairs.
I am replacing the ignition coil (the coil that is on the boat appears to be an automotive style "MSD" coil) andhave bought a Sierra 18-5438 coil to replace it. The shade tree mechanic / old school hot-rodder in me thinks the coil is getting hot at high speed cruise and WOT and once it gets to a certain temperature it breaks down and causes the engine to stumble. The coil may or may not fix the problem, but I need to replace the automotive style coil anyways.
On the new coil there is a sticker that says "Use of External Resistor required if Used on Non-Thunderbolt Ignition Systems". I assume the resistor is for an older "points-type" ignition, which I don't have. HOWEVER: The original ignition system HAD an ignition module attached to the side of the distributor with a single 8 pin connection. The previous owner replaced this module with an remotely mounted module (Denso 131800-7071) with two multi-pin connectors.
My questions right now is this: With the original ignition, was this considered a "Thunderbolt" ignition? And, now that the module has been replaced, is it still considered a "Thunderbolt" ignition? I assume the "Thunderbolt" ignition is just a fancy way of saying its an "HEI" or electronic ignition. If that's the case, I assume I don't need any resistor for the replacement coil, as 12 volts to the coil is what is needed.
Also, any other suggestions on the engine stumble? If the coil doesn't fix the problem, I'm thinking there is a fuel pressure or carburetor issue. The boat starts, idles and runs fine 90% of the time, so I know there is spark, timing is set properly, clean air in and exhaust out and the fuel system seems to be working. One side note, the exhaust bellow from the transom to the outdrive needs to be replaced, as it does not stay attached to the outdrive port. I don't think that would be causing the drivability issues, but I'm admittedly not very proficient with outdrive "stuff".
I have an engine stumble after running at high speed cruise or WOT for several minutes, otherwise it runs great (it even runs great for several minutes at high speed cruise and WOT, until the stumble happens). The engine stumble is a significant RPM drop / loss of power. If you back of the throttle and "nurse it" you can keep the engine running, then continue on at a comfortable cruise speed. The one time the engine died from the stumble, I went to neutral, let the boat stop and turned the key off. The engine started again with a bump of the key, idled and ran fine at a slow/medium cruise all the way home.
I bought the boat 3 summers ago as a non-running boat. I got the boat running after replacing the electric fuel pump, overhauled the carb, set the timing and replaced the plugs and wires, and it has run like a top the last 2 seasons. The previous owner had done some ignition work trying to get it running and now I am trying to work with / around (or replace) some of the previous owners repairs.
I am replacing the ignition coil (the coil that is on the boat appears to be an automotive style "MSD" coil) andhave bought a Sierra 18-5438 coil to replace it. The shade tree mechanic / old school hot-rodder in me thinks the coil is getting hot at high speed cruise and WOT and once it gets to a certain temperature it breaks down and causes the engine to stumble. The coil may or may not fix the problem, but I need to replace the automotive style coil anyways.
On the new coil there is a sticker that says "Use of External Resistor required if Used on Non-Thunderbolt Ignition Systems". I assume the resistor is for an older "points-type" ignition, which I don't have. HOWEVER: The original ignition system HAD an ignition module attached to the side of the distributor with a single 8 pin connection. The previous owner replaced this module with an remotely mounted module (Denso 131800-7071) with two multi-pin connectors.
My questions right now is this: With the original ignition, was this considered a "Thunderbolt" ignition? And, now that the module has been replaced, is it still considered a "Thunderbolt" ignition? I assume the "Thunderbolt" ignition is just a fancy way of saying its an "HEI" or electronic ignition. If that's the case, I assume I don't need any resistor for the replacement coil, as 12 volts to the coil is what is needed.
Also, any other suggestions on the engine stumble? If the coil doesn't fix the problem, I'm thinking there is a fuel pressure or carburetor issue. The boat starts, idles and runs fine 90% of the time, so I know there is spark, timing is set properly, clean air in and exhaust out and the fuel system seems to be working. One side note, the exhaust bellow from the transom to the outdrive needs to be replaced, as it does not stay attached to the outdrive port. I don't think that would be causing the drivability issues, but I'm admittedly not very proficient with outdrive "stuff".
