Hello, I am hoping may get some direction on helping trouble shoot a 1989 Mercury 100hp 4 cylinder Motor. We purchased it used and the motors powerhead had been rebuilt and the motor started upon installation on the boat but never ran correctly. We couldn't get the boat on plane and initially wouldn't turn above 2200 rpms. this is a list what has been done to the boat since then.
Fuel side
New reeds
Replace the fuel lines
Rebuilt Fuel punp
Went through and rebuilt carbs
Installed new needle seats in carbs
Made sure the floats were set correct.
oil injection and syncing of carbs done correctly.
Electronics side
Timing was set to Service manual specs using dial indicator to set top dead center to timing cover. idle timing is currently 2 degrees BTDC.
Max timing (set at 23 degrees BTDC while cranking.) set at 3000 rpm should give us 25 BTDC running
New trigger as of last week
New CDI Stator as of a couple days ago.
Originally before the replacement of the new trigger and the new CDI stator (CDI Part # 174-9710K1) the engine came with the Mercury Red stator that was a two wire with what looked like a black electronics box with ground to the block and the blue and blue/white wires (no red and red white) to the switch box. (The original stator Mercury part number is 9710A11). The red stator must have been put on the motor at some point before we purchased the motor used. Upon doing a DVA test to the coils at running idle the two cylinders (one and two) were firing and had tested within range idling but cylinders 3 and 4 had no spark or voltage reading. The stator?s DVA readings at idle were also testing in range. Not having the ability to swap the red wires with the blues to troubleshoot if the problem would move. We just decided to invest in a new four wire CDI stator (CDI Part # 174-9710K1)and a new oe Mercury trigger. We installed just the CDI stator to see if we would have a change when we recieved the parts, upon installing and testing the new stator and leaving the orignal trigger in, we had spark to all 4 cylinders and the DVA test revealed that at idle the voltage was within range. Note: I questioned why the switchbox before was only sending voltage to just the 2 cylinders??? was it supposed to send it to all 4?? anyway we don't have alot invested in the motor so replacing the stator and trigger were the most logical choices in the troubleshooting.
After the new parts, we put the boat in the water and had change. The boat would get up to 3500 rpm and no more. the motor sounds rough getting there no power out of the hole but an improvement from before. we took the boat out and checked the plugs. Every time ,even before the change, we have tested the plugs one through 4 have come back to look wet and carbon fouled. We are pretty sure we don't have a problem on the fuel side but I am to the point of not counting anything out. We have done the squeeze bulb test each time out to see if it were a fuel starvation issue with no change, it is still almost as though its not igniting the fuel as it should. The switch box and voltage/rectifier both have a 2009 date on them and were there with the motor when we puchased it used. ??? Any tips on a direction to go with the troubleshooting. thanks Glenn.
Fuel side
New reeds
Replace the fuel lines
Rebuilt Fuel punp
Went through and rebuilt carbs
Installed new needle seats in carbs
Made sure the floats were set correct.
oil injection and syncing of carbs done correctly.
Electronics side
Timing was set to Service manual specs using dial indicator to set top dead center to timing cover. idle timing is currently 2 degrees BTDC.
Max timing (set at 23 degrees BTDC while cranking.) set at 3000 rpm should give us 25 BTDC running
New trigger as of last week
New CDI Stator as of a couple days ago.
Originally before the replacement of the new trigger and the new CDI stator (CDI Part # 174-9710K1) the engine came with the Mercury Red stator that was a two wire with what looked like a black electronics box with ground to the block and the blue and blue/white wires (no red and red white) to the switch box. (The original stator Mercury part number is 9710A11). The red stator must have been put on the motor at some point before we purchased the motor used. Upon doing a DVA test to the coils at running idle the two cylinders (one and two) were firing and had tested within range idling but cylinders 3 and 4 had no spark or voltage reading. The stator?s DVA readings at idle were also testing in range. Not having the ability to swap the red wires with the blues to troubleshoot if the problem would move. We just decided to invest in a new four wire CDI stator (CDI Part # 174-9710K1)and a new oe Mercury trigger. We installed just the CDI stator to see if we would have a change when we recieved the parts, upon installing and testing the new stator and leaving the orignal trigger in, we had spark to all 4 cylinders and the DVA test revealed that at idle the voltage was within range. Note: I questioned why the switchbox before was only sending voltage to just the 2 cylinders??? was it supposed to send it to all 4?? anyway we don't have alot invested in the motor so replacing the stator and trigger were the most logical choices in the troubleshooting.
After the new parts, we put the boat in the water and had change. The boat would get up to 3500 rpm and no more. the motor sounds rough getting there no power out of the hole but an improvement from before. we took the boat out and checked the plugs. Every time ,even before the change, we have tested the plugs one through 4 have come back to look wet and carbon fouled. We are pretty sure we don't have a problem on the fuel side but I am to the point of not counting anything out. We have done the squeeze bulb test each time out to see if it were a fuel starvation issue with no change, it is still almost as though its not igniting the fuel as it should. The switch box and voltage/rectifier both have a 2009 date on them and were there with the motor when we puchased it used. ??? Any tips on a direction to go with the troubleshooting. thanks Glenn.
