Mercruiser 7.4 454 CI loss of oil pressure

Discussion in 'Mechanic Recommendation Forum' started by Mike Siner, Nov 4, 2020.

  1. PlayDate

    PlayDate Well-Known Member

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers
    I am sure that Mike just wants to enjoy his boat for a while before he has to pull out his wallet for a material set of investments. I know guys who nursed a bum engine for an entire year to save up the money to deal with it. As to the other engine.....it would seem that if the engines were replaced in 2015.....it may call into question the Previous Owner's assurances. I do believe it would be prudent to compression test both engines and take a look at the plugs. Old engine plugs are easy to identify since they usually foul quickly.

    In regards to Mike's question about where to find replacements......that is more complicated. The boat is 28 years old....so it will come down to what he finds when pulls that engine and how the other engine tests. Unfortunately...it never is just one thing when you re-power. The best case is no damage was done and the cause of oil pressure loss is repaired.

    Anything else will be far more expensive.
     
  2. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Post #1. "Engines run great" with no abnormal noise posted later.

    So why look for replacements? Spending 3k to change an oil pump and hoping for the best makes no sense to me. Does 3k get the motor out of the boat or lifted high enough to pull the pan ?
     
  3. Mike Siner

    Mike Siner Member

    44
    Oct 20, 2020
    1992 Sea Ray 350 Express Bridge
    454 Mercruiser CI
    Found out in 2015, heads and risers were replaced.
     
  4. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    That's it? So the short block was untouched?
     
  5. Mike Siner

    Mike Siner Member

    44
    Oct 20, 2020
    1992 Sea Ray 350 Express Bridge
    454 Mercruiser CI
    Correct
     
  6. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Well that certainly puts a different spin on it. Spending 3k hoping it's the oil pump is a long shot.
     
  7. PlayDate

    PlayDate Well-Known Member

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers
    Sounds like water probably got in and thus the new heads and risers (double down on that if they are raw water cooled). Hopefully the "new" is true.....then all you need are reconditioned short blocks which are not difficult to find. If it isn't I'm getting depressed.
     
  8. Pirate Lady

    Pirate Lady Active Member

    664
    Jun 2, 2020
    None
    None
    Can we get an update?
     
  9. Mike Siner

    Mike Siner Member

    44
    Oct 20, 2020
    1992 Sea Ray 350 Express Bridge
    454 Mercruiser CI
    The boat comes out of the water Feb 22nd for a bottom job, and I'm going to replace the oil pump on the port engine at that time. I’ve taken the boat out a few times, and as long as I keep it below 2500 rpm, there is no issue. Port engine stays at 40 psi, but when I try to get it on plane the pressure dropped to below 5 psi.
     

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