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7.4 Merc oil change

Discussion in 'Technical Discussion' started by Andrew33764, Jan 3, 2018.

  1. Andrew33764

    Andrew33764 New Member

    Joined:
    Jan 1, 2018
    Messages:
    8
    Location:
    Clearwater
    hey guys, I’m new here.

    I don’t normally work on big boats. I helped a guy out for free. He has a 1988 34 Sea Ray with carbed 454 mercs. One engine wouldn’t start.

    Changed the fuel pump, rebuilt carb and put a rebuilt starter on. It’s all good now.

    My question, I changed the oil for him too. I read 6 to 7 quarts with filter?

    I sucked the oil out. New filter, put about almost 5 quarts in and it looked above the full line. I ended up putting 6 quarts in. The other motor a little less. Both looked over full on the stick.

    I went to suck some out and the owner insisted on leaving it.

    Should I trust the stick? Is 5 quarts normal?

    I raised and lowered the boat on the lift to try and suck it all out st first. Also got the boat level for checking the stick.


    Thanks for your thoughts.
  2. 30West

    30West Member

    Joined:
    Nov 14, 2016
    Messages:
    179
    Location:
    Holland, Michigan
    How much over full? The marks on the stick normally are for full and one-quart low. If it is about the same distance above full as to the one-quart-low, you are more than a quart high, as the block begins to widen above the oil pan.

    Have you started and run the engine to fill the filter? That usually lowers the oil level. Dumping and reinstalling the oil filter is an easy way to take out a little oil.

    The danger of overfilling is in having the crank splashing in the oil, turning the oil to foam that won't pump. At higher RPMs the oil pan will not be as full, as more oil is held up in the engine. The danger is more at low RPMs. One quart is very unlikely to cause a problem, more than that I'd be concerned.

    Modern oils are much less likely to foam even when the crank is beating up the oil. I bought a truck that had a strange engine shudder, the dealership had double-filled the oil and couldn't figure out what that shudder was. They took it in on trade after servicing it, pulled the transmission apart and replaced the torque converter, pulled the valve covers, checked everything but the oil level, couldn't figure it out. It was in and out of the dealer several times in my first weeks with my wife driving it, lots of miles with double the oil in our Toyota V8, and never foamed the oil at all. I was pulling the dipstick frequently to check for foaming, fearing a blown head gasket, didn't actually wipe it and check oil level until a couple weeks in. We got a great price, and had the engine gone over carefully by master mechanics flown in to figure it out.
  3. Andrew33764

    Andrew33764 New Member

    Joined:
    Jan 1, 2018
    Messages:
    8
    Location:
    Clearwater
    Yes, I started both motors after the oil change. The guy even took it on a few hour trip and said it ran great. He never goes into high rpms.

    I could have easily used my oil sucking machine to pull some oil out but he wanted to leave it.

    I’m going to let it be and in five months I’ll suck it out and drop 5 quarts in and be done with it. ( checking the stick obviously)

    I hate people watching me work. The mechanical fuel pump was a nightmare.
  4. C team

    C team Member

    Joined:
    Nov 1, 2011
    Messages:
    127
    Location:
    Upper Chesapeake Bay
    Did you change the fuel pump on the starboard engine? I know they are no fun because of the lack of room. Been there done that a few times over the years.
  5. rcrapps

    rcrapps Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    5,050
    Location:
    Jax FL
    Are the oil pans stamped metal or cast?
    Stamped pans should be 5 qts.
    How about the dip tubes, hose adapters on the top ends or low auto version?
    Original engines or PEP-BOYs specials?

    Over filled and foaming oil is not good.
  6. Andrew33764

    Andrew33764 New Member

    Joined:
    Jan 1, 2018
    Messages:
    8
    Location:
    Clearwater
    Changed the port side fuel pump. Holding the rod up to get the bolts lined up is hard. I ended up using a lot of grease to keep it in place.

    I believe they are original engines. 5 quarts sounds like what it would take and not be overfilled. I thought I read 6 to 7 online. I’ve got 6 in the starboard side and over 6 in the port.

    He wants me to check the transmission oil. I said let’s just suck it out and change it/set level correctly. He only wants to ad some if it’s low.

    Wants to buy his fuel filters online because, $6 is too high. Haha

    I changed the fuel pump, starter, oil in both engines. Diagnosed a totally blocked fuel filter in carb. Then decided he needed to have the carb rebuilt. I had someone else do it because I was taking an rv trip. All for 80 bucks total labor. I just like to play around with these big engines. I’m a power sports guy.

    I suggested synthetic oil, Mobil 1. He wanted and got conventional. Would you guys have recommended synthetic?
  7. rcrapps

    rcrapps Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    5,050
    Location:
    Jax FL
    Old LBCs prefer conventional oil. In Florida, straight 30w during the summer maybe 40w if their tired. 15w40 when the weather is cold or the boat does a lot of sitting.
    I feel 5 qt pan. What you read may have been for newer motors or cast pans.
    Depending on the oil filter size and/or remote filter hoses, up to another quart.

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