Goldie627
Lieutenant Junior Grade
- Joined
- Oct 28, 2013
- Messages
- 1,010
1986 Sea Ray
Mercruiser 140 3.0
140 GM 181 I/L4 1982-1986 - 6229718 THRU 0B450800
The good:
Boat starts right up, even with the first cold start. Engine has a small shake but for a forty year old motor, I'm not complaining. Gets on plane, highest rpm i took it was 3200 3300, that was plenty fast enough for me, I'm an old guy just trying to get from fishing spot to fishing spot. Gps from phone, showed speed was about 32mph.
Problem:
Boat has no mid range throttle, wants to gasp and/or cut out, seems like a lean condition in the mid throttle range. Occurs between 900 and around 1200 rpm (grains of salt here, that's by the dash tach).
Accelerating up from neutral or a no wake speed will cause the engine to fall flat on its face, you either have to back off the forward throttle or accelerate past the dead spot. Decreasing speed down from being on plane will cause the motor to run real weak and just sputter along in the dead spot.
Im 98% sure its not the accelerator pump, I rebuilt my old carb 3 times before purchasing the new oem carb and the mid throttle lean condition persists.
My compression results:
1 155
2 165
3 170
4 175
My vacuum at engine idle:
Fluctuates between 13 and 14
Things I've done to trouble shoot, improve performance and overall health of the motor:
I'm truly stumped...
Mercruiser 140 3.0
140 GM 181 I/L4 1982-1986 - 6229718 THRU 0B450800
The good:
Boat starts right up, even with the first cold start. Engine has a small shake but for a forty year old motor, I'm not complaining. Gets on plane, highest rpm i took it was 3200 3300, that was plenty fast enough for me, I'm an old guy just trying to get from fishing spot to fishing spot. Gps from phone, showed speed was about 32mph.
Problem:
Boat has no mid range throttle, wants to gasp and/or cut out, seems like a lean condition in the mid throttle range. Occurs between 900 and around 1200 rpm (grains of salt here, that's by the dash tach).
Accelerating up from neutral or a no wake speed will cause the engine to fall flat on its face, you either have to back off the forward throttle or accelerate past the dead spot. Decreasing speed down from being on plane will cause the motor to run real weak and just sputter along in the dead spot.
Im 98% sure its not the accelerator pump, I rebuilt my old carb 3 times before purchasing the new oem carb and the mid throttle lean condition persists.
My compression results:
1 155
2 165
3 170
4 175
My vacuum at engine idle:
Fluctuates between 13 and 14
Things I've done to trouble shoot, improve performance and overall health of the motor:
- new oem carb
- new electronic ignition conversion kit, included distributor, spark plug wires and coil (sierra 18-5518)
- new spark plugs
- new oem fuel pump
- new fuel lines
- pressure tested and cleaned gas tank interior before powder coating exterior
- new gas tank pick up
- new metal fuel line (from fuel pump to carb)
- timing set just a hair above 6 BTDC
- only use chevron supreme gas
- disconnected/bypassed the shift interrupt
- tried coil with 12v and with resistance wire, no difference
- disconnected the gas tank breather hose
- ran boat on external gas jug (bypassed boat gas tank)
I'm truly stumped...
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