I'm looking at a boat with a 2001 Yamaha 250 EFI ,can anybody tell me what the compression on these engines was new, and what an acceptabe compression would be with 340 hours. Thanks in advance ....Glen
hello usually the bottom is 5 psi lower than the top 2. but the psi spread from 1-2 3-4 and 5-6 should be less than ten psi. you also want a running test of the o2 sensor done to insure it is working and you want to see the records from the last cleaning of the o2 sensor. then see all the maint records for the 100 and 200 hour services. if they have not been done its time to catch up on all of them. good luck and keep posting
Yamaha 250 EFI Compression ?
usually the bottom is 5 psi lower than the top 2. but the psi spread from 1-2 3-4 and 5-6 should be less than ten psi. you also want a running test of the o2 sensor done to insure it is working and you want to see the records from the last cleaning of the o2 sensor.
Linear Mode
