werdnaycart
New Member
Thanks All!!
Last edited:
350 MAG MPI Compression readings
- Thread starter werdnaycart
- Start date
Sous
Member
- Jul 27, 2011
- 671
- Boat Info
- 2009 330 DA, Raymarine C80, Intellian, VesselView, Kohler, Sea Lift, Central Vac
- Engines
- MerCruiser 8.1 Horizons DTS
I'd be a bit concerned by the number 3 and 6 cylinders. You shouldn't see more than a 10% gap between cylinders and your pushing nearly 20%.
CliffA
Well-Known Member
- Dec 29, 2009
- 4,712
- Boat Info
- 2001 Sea Ray 340DA
Name: 'Happy Place'
4.5kW West. Generator
Purchased Nov. 2014
Fresh Water Use
- Engines
- Twin Merc. 6.2L (MPI)
640 hp (Total)
Raw Water Cooled
V-Drive Transmissions
scoflaw
Well-Known Member
- Aug 10, 2011
- 6,395
- Boat Info
- 1999 Powerquest legend 260 sx 502 mag
2005 Baja 242 islander 496
- Engines
- 502 mpi Bravo 1
496 mag B1
Follow up with a leak down test. I had a vortec engine some years back that had 180 readings on the outside cylinders and 150 on the center 2. Turned out the head was cracked between the 2 exhaust valves in the center. Weak link on the thin vortec castings with the 2 exhaust valves next to each other. A previous overheat will/can cause this
Thornton69
Well-Known Member
- Sep 15, 2014
- 1,149
- Boat Info
- 1981 245 SDC
2021 Solar 420
- Engines
- '97 5.7 Bravo 2
'20 Merc 25 EFI Jet
How many hours on the engine? Any irregularities with the plugs in the lower holes? If it has been sitting for an extended period without being ran then it may not be a real big deal. The low cylinders are next to each other in the firing order. This could mean that sitting in the right position, both of either their intake or exhaust valves were open at the same time. Pretty good chance that compression will comeback with some running. As suggested, a leak down test will help identify whether it is losing past rings or valves. If rings a small shot of oil in the holes and recheck compression will help you get an idea how bad it is. It may not be a big deal but can definitely give you some good negotiating leverage if you really like the boat.
