Water in oil and one cylinder

Discussion in 'General Maintenance/Repair Questions' started by NathanH, Sep 10, 2017.

  1. NathanH

    NathanH New Member

    5
    Sep 10, 2017
    2006 Sundancer 275
    5.7L 350 MAG MPI with Bravo III Drive
    Hi All

    I am new to the SeaRay family (Queensland, Australia) and we have purchased a Sundancer 275 that has a Mercruiser 350 MAG MPI and Bravo 3 drive.

    We were out on the river last weekend and noticed minor vibrations prior to anchoring for the day just off the beach. When it was time to leave, the boat wouldn't start. Ended up being a starter motor failing due to the engine being hydrolocked. The mechanic took the exhaust manifold off (I took the starboard side off yesterday) and there is water in one cylinder on the port side. All other cylinders on the port and starboard side look fine to me, no signs of water in the exhaust ports of the cylinder heads however there is water in the oil. (I couldn't inspect port exhaust manifold for cracks due to it being locked up in mechanics shop)

    The mechanic has simply seen the water and told me that I need a new long block because there is a hole in the cylinder head from corrosion and it will cost us $10,500 installed. I don't agree with that outcome by simply seeing some water in only one of the cylinder heads. It is quite an extreme diagnosis for doing no real investigation other than seeing water in the exhaust port of one cylinder.

    I have asked the mechanic to put the boat back in the water as we will need to "save" for this.... I really want a second opinion.

    I want to do a compression test on the cylinders and possibly remove the intake manifold, cylinder heads and head gasket to inspect these areas as well as pressure testing the exhaust manifolds and risers etc. I just cant accept that I need a new long block for water in one cylinder. He may very well be correct but Id like to do my own investigations.

    In saying all of this, the boat will be back in the marina sometime this week. My question is, how far can I tear down the engine without water entering the boat? (raw water cooled) I assume I can block off the raw water intake hose to prevent any water entering or will the water simply not enter due to the fact that the water pump is not operating.

    Sorry if any of this has been covered in other posts. I just want to do my own investigations and get a second opinion before we go to the extreme lengths of replacing the long block.

    Thanks everyone! IMG_0731[2].JPG IMG_0732[1].JPG IMG_0711[1].JPG IMG_0713[1].JPG
     
  2. Thornton69

    Thornton69 Member

    164
    Sep 15, 2014
    BC
    1981 24.5' SR custom hardtop
    1984 18' Valco sled
    1984 20' Alicraft- sold
    5.7 260 Merc/ Bravo 2
    Evanrude 115/80 jet
    You are correct with your concerns. If you are unable to tackle this yourself then I would recommend a second opinion. When you developed the vibration, what kind of rpm and temps were you running? Were any other test done like compression and cooling system pressure testing? Was there other boats running past you while parked on the bank? Several things can hydro-lock a cylinder that cannot be identified by just simply pulling the manifolds. You could have a combination of them that have contributed to this. Condensation in the crankcase can be caused by a cracked head but also as simple as a head or intake manifold gasket. An ignition or fuel problem could have been the initial vibration problem. Would at the least pull that head to identify your problem before writing off the whole works.
     
  3. NorCal Boater

    NorCal Boater Well-Known Member SILVER Sponsor

    Jan 24, 2008
    Covington, LA
    Cobalt CM23
    GM SB 383" Stroker" Alpha Gen I
    Wow! You've got a lot going on here. When I first got the boat I'm rebuilding I discovered water in the oil. The first thing I did before tearing anything apart was to pull all the plugs and do a compression test. All cylinders were at 155 lbs. except one at 100. It was a blown head gasket. I could have ordered an upper motor gasket set and been done with it but I had the heads gone through while they were off.

    I would do the compression test and see what that yields. You may then want to do a leak down test. I've never worked on a Bravo 3 so I'm not sure how the cooling water gets in and out of the boat. I would think though that you could buy some white PVC plugs large enough to go into the hoses at a local home center. Your mechanic seems like he's not quite sure what the problem is and is just going to replace everything.

    Good luck....let us know how it comes out

    Shawn
     
  4. NathanH

    NathanH New Member

    5
    Sep 10, 2017
    2006 Sundancer 275
    5.7L 350 MAG MPI with Bravo III Drive
    @Thornton69 il be honest, I'm not certain of temps and RPM. I know there were no high temp alarms going off but unsure of actual temps. Yep, plenty of boats going past. I will definitely be checking the things you suggest. The only reason I got the mechanic to have a look at it was because we also had a minor gear lube leak so it had to come out of the water for that and then he dropped the news on me!

    @NorCal Boater sure do! Not ideal but will hopefully get through it. First step will be the compression test then go from there. Just need to get the boat back. I understand the mechanics point of view and just replace it all to be sure but I think by doing it myself and taking my time I will hopefully be able to avoid all of that. I'm more than happy to tear down both sides of the motor and replace all the gaskets and have the heads attended too if required.

    Thanks guys, will keep you updated but will take me some time to get to it all.
     
  5. barlow

    barlow Member

    272
    Feb 28, 2009
    Marlborough Sounds, New Zealand
    450 Sundancer
    3116 T/A Cats 350 hp
    Get another mechanic...
     
  6. NathanH

    NathanH New Member

    5
    Sep 10, 2017
    2006 Sundancer 275
    5.7L 350 MAG MPI with Bravo III Drive
    @barlow I think I am with you on that one!
     
  7. BillK2632

    BillK2632 Active Member SILVER Sponsor

    Jun 25, 2009
    Lake Norman, NC
    1999 185 Bowrider,
    Mercruiser 4.3, Alpha I
    +1 on above.
    First, get the water out of the cylinders, turn the engine over a few times and squirt some oil into the cylinders. Also will want to change the oil soon if you are going the fix it route, just don't want the water / oil mix sitting in the crankcase a long time.
    Next, do a compression test, that is going to give you an idea of what problems you have. If the cylinder that had water has low or no compression, then there is damage. Next would be to pull the head on that side and have a look. What usually happens is the exhaust riser fails (they only last about 5-7yrs in salt water) and allows water to mix with the exhaust. When you shut the engine down, water leaks into the exhaust side of the riser and makes it's way into a cylinder through an open exhaust valve.
    As the cycle repeats one of two things happens -
    1) Enough water leaks into the cylinder to cause hydrolock (what will not compress like fuel) and bends or breaks something when you try and start the motor. or 2) not enough to cause hydrolock leaks in, but enough to start rusting things inside that cylinder (piston head, rings, valves etc), this usually causes a rough running motor since that cylinder is not firing.

    If compression checks out good, change the oil, put new risers on and go boating. If not, pull the head on that side, you will find something, wrong with that cylinder - you are going to need to replace the risers and possibly manifolds at a minimum.
    From best to worst it is either -
    1. riser only, good compression - change oil and risers
    2. head gasket - fairly easy to replace
    3. bent / rusted valve - new or re-worked heads
    4. damaged piston - new block as your mechanic suggested. If you end up here, I would look around, there are a number of options from partial, to complete motors.

    Unless you pull the raw water pump off (which you shouldn't) , you should have to worries about water coming into the boat while you do this work.

    My first hand experience with this was #3, engine started running rough, water in the oil - the log style exhaust manifold on this Commander 302 had failed - we re-worked both heads/valves, replaced the manifold and ran the engine for another 1000hrs. So unless you have problem #4, this is not terminal.
     
  8. kap2

    kap2 Member SILVER Sponsor

    121
    Oct 28, 2013
    Rhode Island
    370 Sundancer 1998
    Twin 7.4L Mercruiser V-drive
    +1 on BillK2632 suggestions. One other test to perform is a coolant system leak down test, as noted in an earlier post. That will show if the water in cylinder came from the coolant system rather than the risers. Also, change and flush the oil as soon as possible if you plan on saving the engine.
     
  9. JVM225

    JVM225 Active Member

    Apr 8, 2008
    Farmingdale, NY
    2002 410 Sundancer, Monaco Edition.
    3126 Cats.
    I would just pull the heads and start from there. You may just have a cracked head or blown gasket. Then try spinning the motor by hand with the heads off to see if you have a bent rod. Also, take a good look at the tops of the pistons and the cylinder walls while you have everything opened up.
    After you do all that, then you can make a decision about what you want to do.
    If it's just the heads, you may or may not want to just replace them depending on the overall condition of the motor.
    Around here, a long block doesn't cost all that much more in boat dollars than a set of heads. If your motor is a little tired or questionable you may be better off just repowering.
     
  10. NathanH

    NathanH New Member

    5
    Sep 10, 2017
    2006 Sundancer 275
    5.7L 350 MAG MPI with Bravo III Drive
    I know this is an old thread now but found a pin hole in he port side cylinder head. Top end of engine has been taken apart and I have 2 new cylinder heads and gaskets etc on the way. Bottom end looks in good condition (not seized and bores look and feel good) and had a mechanic take a look that agreed. Deck clearance on all cylinders looks good so I don’t think the crank or anything is bent. Hoping to get things back together again in he next few weeks but I’ll see how I go!

    23508A56-752B-406D-AF82-071D5EC87D4B.jpeg 011E0794-DC3F-4995-A02F-797DC6DFDADE.jpeg
     
  11. BillK2632

    BillK2632 Active Member SILVER Sponsor

    Jun 25, 2009
    Lake Norman, NC
    1999 185 Bowrider,
    Mercruiser 4.3, Alpha I
    Thanks for the update. Sounds like things worked out - not the smallest problem, but not terminal either. Rebuilding the top end like you are doing is common, if done correctly the motor should live a long life now. You didn't mention, but hope you are replacing the risers at minimum and manifolds if needed. The likely root of the hole in that cylinder is a lean condition caused by water getting in - small amounts over time - but enough to lean out that cylinder which will cause it to run much hotter and eventually burn a hole like you have. Once the hole formed, water ran in and finished it off. Check those risers and manifolds!
     
  12. NathanH

    NathanH New Member

    5
    Sep 10, 2017
    2006 Sundancer 275
    5.7L 350 MAG MPI with Bravo III Drive
    @BillK2632 The risers do look sus so I will be replacing them. I have pressure tested both manifolds with water and air and they both held 25psi for an hour and seem In reasonable condition.
     
  13. Sublimetime

    Sublimetime Member

    338
    Oct 22, 2007
    clifton nj
    420 da
    454
    How does the lean condition burn a hole thru the casting above a closed valve.
    Both valves are closed at firing, lean condition preignition usually takes out the piston top as it is the softest and closest to the bang.
    My guess is it was a bad casting that finally let loose.
     
  14. scoflaw

    scoflaw Active Member SILVER Sponsor

    Aug 10, 2011
    cape cod mass
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Agree with you on that. Those vortec castings are thin and looks like the corrosion ate it away from the water jacket side
     
  15. NorCal Boater

    NorCal Boater Well-Known Member SILVER Sponsor

    Jan 24, 2008
    Covington, LA
    Cobalt CM23
    GM SB 383" Stroker" Alpha Gen I
    Understood they look good....now. But what about next year? Why not just replace them and be done with it. It will be one less thing to worry about and give you some peace of mind.

    There is never time or money to do it right but always time and money to do it over.
     

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