5.0 GXI Hydrolock through exhaust

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Aug 1, 2020
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Had boat four years never a hydrolock issue! Had a four blade prop resurfaced and cant even get the boat out of the no wake zone before I have water on top of my Pistons. Did this two times. After the second time I ran it on a hose for 20 minutes pulled the spark plug out of number one and stuck an inspeciton camera in there and its bone dry. Number 1 has been one thats full of water the two hydrolock times. I did put a resurfaced four blade prop that has been on the boat before on before these two failed boat days, but cant fathom any way that would make the exhaust back up. My volvo penta doesnt have exhaust flappers and never has. I will post a video of it running on the hose. It does seem too much water is exiting before the bellow, maybe someone else can tell me if this looks normal. Any suggestions appreciated.
 

alldodge

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Howdy
Most probable is the exhaust is leaking. It only shows its self when in the water because there is more water being pumped thru. I would remove the exhaust and pressure test

Only other reason is the boat is sitting lower in the water from the hull getting water logged maybe
 
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Thanks, I took the manifolds and risers off and did a static acetone test and they didnt leak down over the 15 minutes required. They say acetone is thinner than water so that should act similiar to the water system under 5-10 psi. Of course thats just what others suggested. But you may be right, my dealer didnt have a way to pressure test is the reason I went with acetone. Plus it only takes two minutes and I havn't run the boat hot. We ran all day on the 4th of July. I came home changed the prop, put it back in the water, within 2 minutes pistons were full.
 

alldodge

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Hasn't run hot but could be a head gasket, could try compression test

Could also pressure test the block. Plug the exhaust hoses and drain block, then pressurize at the Stat
 
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I was gonna try that but it runs endlessly on the hose which kinda lead me away from that. Not saying that’s not the problem though. Of course head gasket and manifolds/risers leaking are for sure the first couple of places to think about so maybe I should just back up and start at the beginning. I just was led toward exhaust. First time I got 75 yards from boat launch. Second time I didn’t even unhook it from the trailer. And it filled up and locked down in two minutes. That’s really quick for that much water.
 
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to add to my confusion,........

I ran it on the hose 20 minutes took out a spark plug, no water,

i take it to the lake ran it 22 minutes to be exact, i Put it in the water floating but not off the trailer, took out a spark plug that is always full of water #1 and it was dry as a bone at I was running it at 1500-3000 rpm

Put the boat in gear, tied down flat on the trailer put it in gear for less than 2 minutes at about 1500 rpm, cla clank, pistons full

Thats the third time I've locked it up, all three times the prop was turning and it took less than three minutes, cant get one drop on a hose or blacked into the lake without spinning the prop,

I'm clueless
 

alldodge

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A hose is unable to supply the same amount of water that the pump can pump, so there is next to no pressure building. In the water, pressure does increase and this allows water through where ever the crack is

Since its always #1, pull the port head and have a look
 
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yes, thats why i took it to the lake and backed it down in the water and ran it in the water for over 20 minutes without it in gear. Its not always just number one, its in every cylinder, I just check number one. HMMMM
 
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