14883 Mercruiser SCREW, COUPLING

Introduction
The problem that is identified below does not have a known permanent solution. Until a permanent solution is known, use the solution that is identified below.Problem
The coating on the wastegate (WG) shaft is known to swell. The resulting decrease in bushing clearance may cause valve to stick, or seize.Solution
Do not operate or work on this product unless you have read and understood the instruction and warnings in the relevant Operation and Maintenance Manuals and relevant service literature. Failure to follow the instructions or heed the warnings could result in injury or death. Proper care is your responsibility.
Speed instability at several sites has been successfully resolved without having to rebuild the WG.The procedure described here is intended as a troubleshooting guide to find true root cause of engine instability, and provide alternative solutions to rebuilding the WG.The coating on the WG shaft is known to swell. The resulting decrease in bushing clearance may cause valve to stick, or seize. The current ECA / ICA is to rebuild the valve with new replacement shaft and bushings. If parts are not available and coating on shaft is still intact, the excess swollen shaft material at the bushing interfaces can be machined back to Cat specification of 19.5 0.013 mm.Cat is investigating alternative material wear-pairs as potential PCAs.Diagnostic List
Verify that waste gate linkage is set correctly per instructions below. This is the preferred method to ensure that the plate does not contact the housing at initial setup.
Adjustment of the linkage is required to ensure that in the closed position, the WG plate does not contact the housing during operation. With the WG plate touching the housing in the closed position and the actuator fully extended, shorten the length of the WG rod by turning the rod 2 full turns and secure in place. Verify that plate is not touching housing when actuator is at full extension.
Final adjustment of the WG rod length is verified when the commanded position of the WG is approximately 40% at rated speed and load. Shorten or lengthen the overall rod length to achieve this commanded position of 38% +/- 2%.
Verify that compressor outlet bellows are intact and there are no other boost leaks in the intake air system.
Verify that the IMAP Sensor or Pressure Module is working correctly.Note: 16 Cylinder ONLY: Check Pressure Module lines for condensation.
Verify condition of hydrax oil and possible contamination of system. Document hydrax pressure.If above steps do not resolve issue, follow the procedure below and take Cat® Electronic Technician (ET) data log during entire procedure.
Set all needle valve to 2.5 turns open.
Disable NOx feedback.
Input fuel quality and specific gravity.
Load engine in PC cal to 100% speed and load (or highest stable point) and verify that problem still exists outside of feedback with no known good value stored in NOx sensor. Install calibrated emissions analyzer to verify tune up.
Physically look at WG lever arm at highest stable rating – if possible document with video and send back via DSN.
Load step down to 75% load to get clear picture of actual WG motion vs ECM WG cmd.
Load step up to 100% load to get clear picture of actual WG motion vs ECM WG cmd.
How is lever arm moving in relation to the WG cmd?
If stuck and not moving, skip to Step 11.
If unstable, go to step 11.
If stable, put engine into closed loop and verify emissions, stop troubleshooting.
Verify NOx sensor calibration.
Enable NOx feedback.
Allow engine to stabilize at 50 ppm
Increase hydrax oil pressure up in 10psi increments (300 psi max) until stable. If not stable, shut down engine.
Replace the hydrax actuators and repeat Steps 4 through 9.
G3616 ONLY: If evidence of condensation exists in IMAP lines at the pressure module, replace pressure module, or swap with known good one. This has proven effective at resolving the instability at several sites. (Moisture build up in module impacts output signal)
Repeat Steps 4 through 9. If instability remains, proceed to Step 11.
Is the WG stuck and completely unable to move?
Document what position the WG is stuck at.
Remove housing fully assembled from engine.
Verify that butterfly plate is installed correctly and not contacting housing.
Check the ID of the housing for witness marks of the plate contact.
Is the butterfly plate centered in the bore?
Photo document (facing down looking at butterfly & also from side showing lever arm position).
Verify that valve will not turn by hand.
Rebuild WG with new shaft and bushings. Document if bolt holding shaft stop to the thrust washer (opposite end from lever arm) is loose.
Return failed parts to factory along with the data logs, videos, and pictures.Channel List for Data Logs
Table 1
Cat ET Status Parameter Name
Engine Load Factor
Engine Intake Manifold #1 Temperature
Air Filter Differential Pressure
Engine Gas Supply Pressure
Engine Speed
Actual Engine Percent Torque
Desired Engine Speed
Engine Gaseous Fuel Correction Factor
Engine Fuel Specific Gravity
Engine Air to Fuel Differential Pressure(1)
Engine Fuel Valve #1 Position
Hydraulic Pressure
Specific Heat Ratio
Air Filter #2 Differential Pressure(2)
Fuel Energy Content
Engine Intake Manifold #1 Absolute Pressure
Engine Exhaust NOx Level
Desired Engine Exhaust NOx Level
Emissions Feedback Mode
Engine Exhaust NOx Level Sensor Status
Wastegate Position Command
Choke Position Command
Actual Air to Fuel Ratio
Intake Manifold Air Flow
Gas Fuel Flow
(1) G3616 ONLY
(2) G3612/G3616 ONLY