Hi,
I'm having some issues with my motor. Below is everything done so far. Looking forward to your help.
2003 4.3 MPI Mercruiser
Seawater and Closed Cooling
Boat runs in fresh and salt water. After running in salt water always flushed for 10-15 minutes with fresh water and Salt Away.
While running boat in fresh water had an overheat condition occur (seawater water pump recently replaced). Heated to the point the lower rubber exhaust tube, Port side, was smoking but not leaking. Cooled engine down and drove back to the launch ramp watching temperature closely.
Replaced rubber exhaust tube. Also removed both exhaust elbows, inspected and cleaned. Surfaces appeared good. Port side wall thickness was thinner than starboard side. Test ran in driveway. Turned over harder than normal but ran good. Took to water and went to start. Cranked very hard. Pulled plugs and had water in #1 and #3. Turned over and removed water from cylinders. Started boat and ran for about 10 minutes. No overheat but boat was under powered. With motor running removed spark plug wires one at a time. No difference noticed with #1 & #3 so I know I had a problem with those 2 cylinders. Suspected bent pushrods and issue with Port exhaust elbow and / or exhaust manifold.
Brought home and did cold compression test.
#1 – 145
#2 – 152
#3 – 180 (water was in cylinder)
#4 – 150
#5 – 165
#6 – 155
Pressure tested seawater system with 20 psi air. Found no obvious leaks. Removed Port exhaust elbow and manifold and pressure tested separately 20 psi with no leaks. Exhaust manifold mating surface to exhaust elbow had suspect area of concern. Also due to wall thickness of exhaust elbow suspected poor sealing. Gasket showed no obvious signs of leaking. Purchased new exhaust manifold and elbow.
Before reinstallation removed all push rods from port side. All appeared straight. No obvious damage to valve springs. Rotated engine by hand and observed all valves moving. Also noted water in oil. Attempted to pressure test each cylinder on port side with 140 psi but could not hold crank in place. Assumed no bent valves.
Reinstalled new manifold and riser. With engine not running, and port spark plugs removed, pressurized seawater system. No water in cylinders. Started engine and it ran rough. After a couple of minutes alarm sounded (steady) and 2 red lights came on. No overheat. Pulled plug wires one at a time and #! And #3 definitely not working. Suspecting head gasket but would like some opinions thanks.
I'm having some issues with my motor. Below is everything done so far. Looking forward to your help.
2003 4.3 MPI Mercruiser
Seawater and Closed Cooling
Boat runs in fresh and salt water. After running in salt water always flushed for 10-15 minutes with fresh water and Salt Away.
While running boat in fresh water had an overheat condition occur (seawater water pump recently replaced). Heated to the point the lower rubber exhaust tube, Port side, was smoking but not leaking. Cooled engine down and drove back to the launch ramp watching temperature closely.
Replaced rubber exhaust tube. Also removed both exhaust elbows, inspected and cleaned. Surfaces appeared good. Port side wall thickness was thinner than starboard side. Test ran in driveway. Turned over harder than normal but ran good. Took to water and went to start. Cranked very hard. Pulled plugs and had water in #1 and #3. Turned over and removed water from cylinders. Started boat and ran for about 10 minutes. No overheat but boat was under powered. With motor running removed spark plug wires one at a time. No difference noticed with #1 & #3 so I know I had a problem with those 2 cylinders. Suspected bent pushrods and issue with Port exhaust elbow and / or exhaust manifold.
Brought home and did cold compression test.
#1 – 145
#2 – 152
#3 – 180 (water was in cylinder)
#4 – 150
#5 – 165
#6 – 155
Pressure tested seawater system with 20 psi air. Found no obvious leaks. Removed Port exhaust elbow and manifold and pressure tested separately 20 psi with no leaks. Exhaust manifold mating surface to exhaust elbow had suspect area of concern. Also due to wall thickness of exhaust elbow suspected poor sealing. Gasket showed no obvious signs of leaking. Purchased new exhaust manifold and elbow.
Before reinstallation removed all push rods from port side. All appeared straight. No obvious damage to valve springs. Rotated engine by hand and observed all valves moving. Also noted water in oil. Attempted to pressure test each cylinder on port side with 140 psi but could not hold crank in place. Assumed no bent valves.
Reinstalled new manifold and riser. With engine not running, and port spark plugs removed, pressurized seawater system. No water in cylinders. Started engine and it ran rough. After a couple of minutes alarm sounded (steady) and 2 red lights came on. No overheat. Pulled plug wires one at a time and #! And #3 definitely not working. Suspecting head gasket but would like some opinions thanks.
