Taking on water with flush adapter cap open

[skydiveD30571]

9/2006 Volvo 5.0 GL-H and SX-A outdrive.

I took it out last night to water test some idle adjustments I had made. It seemed to be running really well from idle to WOT for a couple hours. Idle was consistent at 600rpm with no surging.

We were cruising around pretty slow, about 2500rpm, and I looked down and saw the temp had risen to about 200deg. It has never gotten over 175 before, so I immediately shut it off and went to the compartment to investigate. When I first opened the hatch, I could hear a bubbling noise just like if you hold a can or water bottle under water and it fills with water. I knew I was taking on water but the bilge was completely empty. I stuck my head out and noticed the transom was much deeper than it has ever been. The swim platform usually sits off the water atleast a foot, and was now just a couple inches above.

I immediately raised the outdrive to see if it made a difference. When I stuck my head back in the engine compartment to listen for the noise, I noticed the cap for the hose flushing adapter came off. Well that explains my overheating issue, being that the impeller was now sucking air from there instead of water from the lower unit intake. I closed it and waited for the temp to naturally drop back down. I always keep an eye on oil/temp so I guessed it was running that way no more than 30 seconds or so, so after about 20 minutes of cool-down time I started it up and watched the temp very closely to make sure the impeller wasn't now shot. Temp rose to 170 and never moved again. Eventually the water I had taken on was released and the transom returned to its normal position.

For the rest of the day, it would idle perfectly after a choke start but after pulling a wakeboarder and returning to idle it would constantly surge (from about 200-600rpm) and would usually die unless some throttle was given.

Obviously this ordeal concerned me on many levels. It's not fun to feel your almost-new-to-you boat starting to sink while no water is actually visible. I got to thinking last night what could have caused this. Since the raw water pump system is air tight, if that flush adapter cap is open would it be essentially like opening a vent which then allows water to rush in through the raw water intake on the lower unit since a lot of that system is under the water line? Even then, it seems like it would require a lot of water to bring the transom that far down. Is it possible that any of the water could make it to the engine block? I'm wondering if the surging idle after pulling a load is a result of this, or if its just my usual idling issues getting worse and coincidentally happening at this time. I'm taking it to a mechanic today to get a general tune up and check the timing etc, is there anything I should specifically ask him to check after this happened?

As always, thanks everyone for your input. Being that it ran perfect afterwards (besides surging idle) I don't think it caused any damage, but I know better than to just assume and then have it bite me 10 times worse later.

 

[bruceb58]

Re: Taking on water with flush adapter cap open

Change your impeller. It may have run dry and damaged it.

I think you were imagining the boat sitting lower if there was no water in the bilge. Maybe more people in the back of the boat than normal?

So where was this water you had taken on?

 

[Maclin]

Re: Taking on water with flush adapter cap open

If you think the engine took on water just look at the dipstick. Even if it did though, you could net get enough water into the engine crankcase to make much difference in weight, the nasty brown/white milkshakey oily water would come blasting out anywhere it could just before the engine died if it had started filling up with water.

 

[skydiveD30571]

Re: Taking on water with flush adapter cap open

I've had several heavy people on the swim platform before and it never sat as low as it got the other night. The other 4 people were up by the bow, I was the only person at the stern. It definitely took on water, but not in the bilge. It had to be coming thru the raw water intake, and I'm guessing collected in the manifolds. My mechanic said he has heard of this happening before, and my guess as to why it happened was correct. With the hose flush adapter open, it basically acted as a vent allowing air to escape and water to come in thru the raw water intake since it is below the water line. I agree, it seems like it would take a good amount of water to bring a transom down almost a foot.

After about a minute it quit taking on water, I'm guessing when all parts of the water intake that are below the waterline were full. Once I secured the adapter cap and started it up, it ran perfectly fine the rest of the day and the transom returned to its normal height above the water.

Maclin I watched for anything unusual like you stated, but there were no oil leaks, or rise/fall in pressure, and the engine didnt die. The mechanic also said if the block took on water that it would be very evident. I noticed nothing out of the norm. I'm pretty sure all is good but wanted to make sure.

 

[Maclin]

Re: Taking on water with flush adapter cap open

Odd situation. Good news, and I agree, that the engine is probably just fine. Also good news that it probaly won't happen again unless that cap is cracked or something and just won't stay on.

What kind of boat is this? How big, style etc. Does it have an automatic bilge pump? Does it have more than one bilge pump?

I'm kind of spitballin' here, but maybe the bilge pump did not kick on right away, like the float switch got stuck maybe, or other type switch has a problem, and it didn't pump out until you walked to the back and it kicked on during this time. From your description of events this is not all that believable either, unless the water in the bilge was so clear and ripple-less as to be invisible!

There is just not enough capacity in the cooling system to hold enough water to make it that much heavier. Basically that same amount of water is in the cooling system the whole time when the cap is on. If the bilge had no water then I am going to have to stop thinking about this!

Good luck, have a good season!

p.s.
I am from Wichita, spent first 50 years there, until 2003. Frequented Lake Afton and Cheney and ElDorado in the 80's, sometimes Wilson Res, then we started going to Marion this century Just moved our boat here to Texas, have not got into a routine here yet. The vid in my sig was captured at Marion.

 

[bruceb58]

Re: Taking on water with flush adapter cap open

Like Maclin said, your cooling system is completely full of water anyway. Even with that, we are only talking a few gallons here.

 

[Don S]

Re: Taking on water with flush adapter cap open

Every Volvo that I ran into with a missing or loose cap, suck air not water, and burned up the impeller and overheated the engine.

 

[skydiveD30571]

Re: Taking on water with flush adapter cap open

Even though the temp was over the normal range for less than a minute, i pulled the impeller to take a look at it. All is well, and thats what I expected since it's been running at a great temperature since that incident. I wonder how the cap came off since it is threaded just like a hose. I'll keep an eye on it and if it happens again I could just seal it up and use muffs instead.

I decided to quit wondering where so much mystery water was hiding. As long as it doesn't happen again, and didn't cause any damage, I'm just going to chalk it up as "one of those things."

It's funny how small the world seems sometimes. This happened at cheney on Wednesday night. I've heard marion is a nice place I plan on trying it out.

Definitely an odd situation I thought I'd share with you guys. Thanks for the input.