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350 chevy engine

Discussion in 'Chevy Trucks' started by johngus, Oct 20, 2003.

  1. johngus

    johngus Senior Member
    Messages: 117

    I know this is a truck section but I know the techs on here are the best.I have a 350 in my boat.A few weeks ago the engine was hydrolocked,after removing the plugs I found some water in # 5 cylinder.I removed the manifolds and risers and presure checked them,they checked out OK.The boat seemed OK until this weekend it happened again,On startup it cranked a few revolutions then locked up.I removed the plugs again and found a large quanity of water in all cylinders,especially the middle 2 on both sides.Compression comes up at 140-150 all cylinders so I don't think head gasket.Could it be the intake manifold is rotted through?How does the coolant circulate through the manifold?The boat is being hauled this weekend so I'm trying to figure my plan of attack for when I get it home.I was figuring on a cylinder leakdown to start to make sure no headgasket issue first but not really sure about my next plan without ripping it apart.I really want to find the problem before the rip down.sorry this is so long but I'm frustrated with this.
  2. wyldman

    wyldman Member
    Messages: 3,265

    Coolant circulates from the water pump into the block,up into the heads,and back out the front of the intake.If the intake gasket leaks,it would be one of the front or rear cylinders that would take on water.If the manifold rusted out,it would be the same thing.That's the way it is in a car\truck engine.Don't know if the boats are any different or not.

    Could it be ingesting water somewhere else,like throught the carb or something ?

    If not,I'd say you probably have a bad head gasket or a cracked head.
  3. festerw

    festerw Senior Member
    Messages: 986

    The marine engines are the same as the car/truck engines except for a few "special" parts, sealed starter, flame arrestor, blah, blah, blah.

    It sounds like it is sucking it in somewhere, only because even if it was a head gasket that would mean that both sides went at the same time, which seems very odd to me.
  4. wyldman

    wyldman Member
    Messages: 3,265

    I figured they were pretty much the same.I agree,the head\head gasket should only fill up one side,but maybe it's pumping the water up across the intake before it locks up when he tries to crank it.

    This boat doesn't have water cooled exhaust manifolds or anything does it ? I've seen something like that before (again,i'm no boat expert here),and maybe one is cracked and the water is coming in through the exhaust ports ?
  5. Crazy_Eddie

    Crazy_Eddie Member
    Messages: 38


    You can also go to http://www.wmi.org/www/boating/boatboard/ and do a search. If you can't find the answer, post it (I think you have to register to post though). There is a guy there named Dunk, he's the wyldman of boating, he'll get you some answers.
    You can also go to http://www.thehulltruth.com and go into their boater's forum and ask there, but I think you have to register to veiw any posts...

    good luck...

    EDIT: A quick search pulled this up...

    7/27/00 12:05:00 PM Bayoudog ( from TEXAS says Hyrdolock
    Hydrolock means you have water in your cylinders, a real bad situation, especially if left unchecked, and more so especially if it is saltwater (hopefully it's all freshwater in Utah!). Have you had your risers replaced since new? At least, have you had them examined? The inner jacket wall in risers tends to collapse after a few years (5 years is just about right) and allows water to drain back into the cylinders, causing hydrolock. That's the only thing I can think of that is causing it. As far as not pulling tubes or idling engine a few minutes before shutdown... that isn't what your mechanic is telling you, is it? I would find me another mechanic in a hurry if that was the case.


    7/28/00 12:58:00 AM P.v. ( from WASHINGTON says dieseling can/may/will lead to engine running backwards...
    Engine running backwards momentarily can injest water from exhust. Yes, not good. Make sure the motor is in tune. Humor me, go look at the bulletin. It won't cost you a dime. I would agree that you could need exhust elbows due to erosion. You probably don't need extensions for your manifolds/elbows as everyother Bayliner Capri would have also needed 'em also. And they did'nt. I've seen alot of dieseling this year than in the past mostly due to the weather. Hot!! But, ask around about what could cause a motor to run backwards for a moment. Then ask what could be the result ..
    Last edited: Oct 21, 2003
  6. johngus

    johngus Senior Member
    Messages: 117

    It does have water cooled exhaust.I pressure checked the manifolds for cracks already and theare OK.The risers were replaced last season but that probably doesn't mean much especially with salt water.thank you for the link to the boating site and interesting thought Wyldman about the headgasket leaking and water sucking across intake manifold.I too thought it would be hard for both heads to blow at same time.I just bought this boat a few months ago and the motor was supposedly replaced in 1999.Who knows the actual truth.It looks real clean is freshly painted but that doesn't mean much.It's being hauled Sunday so I'll see when I get it home.I'm gonna pull the motor and go over it anyway just to make sure the water didn;t damage anything.I'm also gonna try to pressure check the exhaust m,anifold and riser together.will post back my findings