VP 8.1 Gi-F w/DPS - Hydro-locks using blue flush connector when boat on trailer

S4ordie

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May 6, 2017
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Hi Volvo Pentians, I need help. I am not new to boating, have owned saltwater sportfishers and sailboats over the years but did just buy my first trailer boat. A low hour (135hr) 2006 Cobalt 220 with the VP 8.1 Gi-F engine and DPS. The previous owner hydro-locked the engine when it was out of the water and on the trailer. He used the blue freshwater flush connector. He said he connected it, climbed down from the boat to go turn the water on (high as described in the VP owner’s manual), climbed back on the boat and turned the ignition. Nothing. He towed it to a marine engine shop where they confirmed water in some of the cylinders. They blew the water out, bore scoped each cylinder and compression tested all as well. Everything was good. Tech started the engine in the shop using the same blue flush connector, engine ran fine, came up to temperature. He idled it for more than 1/2 an hour, also ran it up quickly a couple of times to 2500 rpm. All was good. Based upon the tech's positive feedback I agreed to sea trial the boat with the owner. We had it out for more than an hour and ran it under all conditions. Ran perfect. This was in San Diego and in salt water.

I bought the boat and hauled it back to Phoenix. I then flushed the salt out of the engine and risers. I hooked up the hose to the blue flush connector, turned the faucet all the way on, good water flow out of the sterndrive exhaust, and started the engine. It ran good, came up to temperature and I turned the engine off and disconnected the hose form the blue flush connector.

Today, in preparation for my first launching of the boat tomorrow, I decided to run the engine one more time just to make sure everything was okay. Connected the hose to the blue flush connector, turned water on, tried to start engine. Quick groan and nothing. I suspected it was hydro-locked again so I pulled a plug and indeed, clean fresh water was in the cylinder. I will remove all plugs, pull the ignition relay and will turn the engine over a few times to get the water out before connecting muffs on the sterndrive and starting the engine that way.

I called the previous owner and queried him more about the hydro-locked scenario. He said he always used muffs prior to the last time he flushed the engine and after reading more about the simple blue flush connector he decided to give it a try and it hydro-locked the engine. He then went on to confess he had over heated the engine last summer when he ran through some mud during low tide. He had the water pump and impeller changed then.

Thanks for reading through this long post, but my question is, why or how, can water migrate through the blue connector into the intake manifold and subsequently the cylinder in less than 1 min? Could it have something to do with the sterndrive being tilted up? It was up this morning – last time I flushed the drive it was in normal running position as I had been cleaning it. Could something have happened when it overheated last year that would allow water intrusion? The engine ran perfectly fine during the sea trial three weeks ago. Oil is clean, no evidence of moisture or water in it, so I am ruling out the head gasket. The engine also has good compression in all cylinders. The risers were removed and inspected by the tech in San Diego. He said they looked good (I trust this tech. I lived in San Diego for 20 years and used this same guy numerous times).

A doozy of a first post I know. I do thank all for any input provided.

Dan
 

spoilsofwar

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Jun 29, 2011
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1,124
The blue hose port is not the issue here. If water got into the cylinders when it was run that way, it will get into the cylinders when it is run any which way; the blue port connects to a hose simply tee'd into the water intake hose from the drive. So the issue is more: "why is water getting into my cylinders?"

Side note; don't run the engine with the drive tilted up past the "beaching" range. You don't mention how far it was up, hopefully not in the trailering position, but whether it's on the hose, muffs, in the water, whatever, that's really hard on the ujoints.

With any luck, someone more knowledgeable on water in cylinders will come along to help you now.
 

S4ordie

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May 6, 2017
Messages
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The blue hose port is not the issue here. If water got into the cylinders when it was run that way, it will get into the cylinders when it is run any which way; the blue port connects to a hose simply tee'd into the water intake hose from the drive. So the issue is more: "why is water getting into my cylinders?"

Side note; don't run the engine with the drive tilted up past the "beaching" range. You don't mention how far it was up, hopefully not in the trailering position, but whether it's on the hose, muffs, in the water, whatever, that's really hard on the ujoints.

With any luck, someone more knowledgeable on water in cylinders will come along to help you now.


Thanks for the feedback. The outdrive was tilted up in the trailering, I assume same as beaching, position. There is nothing in the owner's manual regarding fresh water flushing that says anything about the drive having to be down in running configuration. I now understand how that can be tough on the joints, but wouldn't that only apply if it were in gear?

I'm not sure the condition of water intrusion is the same anytime the engine is running. Perhaps having the drive in beaching position combined with using the blue flush connector causes just enough back pressure to push the water up into the intake and down into the cylinders. Weird stuff.

EDIT: For clarification, the two times the engine hydro-locked it was not running. Fresh water hose connected to blue flush connector, water turned on, then turned the ignition. Not one revolution of the engine.
 

spoilsofwar

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Jun 29, 2011
Messages
1,124
Do you think your ujoints don't turn when the engine is running and the drive is out of gear? Ujoints spin regardless of gear selection.

I used the wrong terminology, maybe you were confused by it; "trailering" range is actually called "tilt" range. Anything over 30* with the engine running is a no-go as per the VP owner manual.

IMG_1238_zpspjr13vmh.jpg


As for the water issue, I can't see it. Water is water. Maybe the hose pressure makes a difference versus water pressure in a lake, etc, but I can't imagine how.
 

S4ordie

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Joined
May 6, 2017
Messages
4
Do you think your ujoints don't turn when the engine is running and the drive is out of gear? Ujoints spin regardless of gear selection.

I used the wrong terminology, maybe you were confused by it; "trailering" range is actually called "tilt" range. Anything over 30* with the engine running is a no-go as per the VP owner manual.

IMG_1238_zpspjr13vmh.jpg


As for the water issue, I can't see it. Water is water. Maybe the hose pressure makes a difference versus water pressure in a lake, etc, but I can't imagine how.


Great info! Thanks. Fortunately the engine never lighted so no concerns. I noticed two of the spark plugs were cracked when I removed them. They are expensive, but will replace all of them.

Dan
 

S4ordie

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May 6, 2017
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More info.... After replacing all of the spark plugs I began thinking more about the tilt of the outdrive when it hydro-locked. The two times it has occurred was when the drive was all the way up in trailer mode. Soooo, as a test I lowered the drive, hooked up the hose to the blue fresh water connector, turned it on high again and tried staring the engine. Voila! It works. I turned the engine off, let the water run for 10 mins and attempted to start the engine again. Fired right up. Could be having the outdrive all the way up in in trailer mode effects water flow and causes just enough back pressure to make it flow into the intake then engine causing it to hydro-lock before turning over.

Still interested in other's thoughts and opinions on this matter.

Dan
 

skydiveD30571

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Feb 13, 2012
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1,042
I'd be very surprised if the drive angle had any affect whatsoever on water intake. Having the same system and knowing it pretty well now, I don't see any correlation. The flush connector is T'd to the intake line (which runs from the drive intake opening where muffs usually go) right in front of the water pump. The pump creates vacuum and sucks water in, then creates pressure and sends it to the T-stat housing where it will either route to the exhaust and out, or the circulation pump depending on temperature.

The main reasons water can get into the cylinders if either from backflow through the exhaust while the boat is in the water (not very common because of the higher risers) or a crack in the water jacket around the cylinders. Do you ever shut off the engine while the boat is still moving, or not let it idle before shutting off?
 
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