1999 Mercruiser HI-Performance GM 377 EFI Engine Service Manual, Page 236Get this manual

1999 Mercruiser HI-Performance GM 377 EFI Engine Service Manual, Page 236

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INSTRUMENTATION
aIndicator

Vacuum Gauge
TESTING
1 Disconnect vacuum hose from engine2 Connect service vacuum gauge to engine and record engine vacuum readings at idle, 1