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Old 01-08-2021, 02:16 PM   #1
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Aqua-lift

I have a 1980 Chris Craft Commander 410, with twin 454's.

The boat had been sitting neglected for a LONG time. We rebuilt the carb on the port engine and got it to start - but it had a bad rattle the sounded like valve lifters. Replaced those, then had a series of issues that kept us from getting the engine to start for weeks...

Finally got to the point that we were able to check compression, and discovered that the exhaust tube from the port and starboard exhaust manifolds to the aqua-lift muffler was completely full of water. (Not sure it's an "aqua-lift" brand - but it's a big fiberglass vertical cylinder that the exhaust pipe feeds into, then goes to a wet exhaust hose that goes overboard.)

We've drained the water in the exhaust pipe (and are also repairing a crack in that pipe). Next will be to see if we can finally get a compression reading.

QUESTION: Is there a reasonably simple way to ensure that the exhaust port exiting the boat (and aqua-lift) aren't plugged up? (I have no idea what's in the water muffler - is it just a big cylinder, or are there baffles, etc? The path from the muffler to the exit has several turns - so it isn't obvious to see whether it's blocked or not.)

We had cycled and cycled the engine many times playing with timing, etc, trying to get it to start, without the engine actually running. Could that be what caused all the water to build up in the exhaust tube? I'm confident I didn't have water coming into the exhaust from outside.
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Old 01-08-2021, 09:54 PM   #2
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When you crank and crank an engine with a raw water pump and the water exits the exhaust, you'll fill the muffler because there's no exhaust pressure to push it out. Usually when working on an engine, the seacock is closed. Continual cranking the engine, in some boats will allow water to enter the cylinders. If you're doing extensive cranking, it's best to close the seacock and remove the raw water impeller.

I have drains on my mufflers that open automatically and drain the muffler when there is no exhaust pressure. It makes it easier to start.
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Old 01-08-2021, 10:04 PM   #3
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Similar to Lepke, I have manual drains on my lift mufflers. If there were to be anything other than an instantaneous start, I would open the valve until the engine is running. While my exhaust riser prevents water from going back into the turbo, I don't want a water filled lift pump adding additional back pressure.

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Old 01-08-2021, 11:42 PM   #4
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Thanks guys!! I was thinking I'd read that somewhere, and it makes total sense.

With it being gas engines, with water backing up in the exhaust, I think it probably did get back into the cylinders through the open exhaust ports... Hopefully didn't do any permanent damage!

And, certainly explains how we could have gotten an exhaust pipe full of water. Hopefully there isn't any blockage in addition to that. But I would be curious if there's an easy way to test for blockage - other than just watching to see what happens once we get everything cleared, cleaned out, and back together again.

A drain on the exhaust sounds like a good idea - though I'm not sure how to implement that. The exhaust outputs from the manifolds are 3-3.5" in diameter. Not like I can just insert a Tee with a valve...

What's in the lift muffler? Is it just a big box / cylinder, or are there baffles in it?
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Old 01-09-2021, 07:24 AM   #5
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IF it is a lift pump the discharge feed will have a pipe inside the cylinder that allows the coolant to be pushed up and out.
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Old 01-09-2021, 07:53 AM   #6
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A lift muffler has nothing in it but the pipe in and pipe out, no baffles or bulkheads.

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Old 01-09-2021, 08:14 AM   #7
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The drain goes as close to the bottom of the lift muffler as possible. Usually you just drill and tap, depending on what the muffler is made from and the wall thickness. Most boats in cold climates have a drain to avoid freezing damage to the muffler. Mine are fiberglass and came with a drain hole but no valve. Valve has a weak spring that holds the valve open when there is no exhaust pressure. As soon as the engine starts, the valve slams shut.
Even with the valve, when cranking for maintenance, like valve adjustment, I have to shut the seacock because the raw water pump puts out more water than the valve can handle. I usually pull the impeller during maintenance.
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Old 01-09-2021, 10:15 AM   #8
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Look closely around the base of those mufflers. There's what looks like a metal plug in mine on the outboard side that I think is for a drain (never pulled the plugs). They're definitely not hollow inside, as they're a water lift muffler. Not sure if the factory stuff Chris Craft used is single or 2 stage lift though.

There's no readable markings on mine after 35 years, but if I had to bet based on the mufflers and the bits of fiberglass tube in the exhausts, I'd say they were probably made by Centek.
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Old 01-09-2021, 11:02 AM   #9
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Not a bad idea to remove the exhaust hose from the manifolds while working/adjusting the engines. Sure you'll get some water and exhaust gas in the boat but the bilge pump will take care of the water and don't run the engines very long because of the exhaust. Once the engines are running fairly well hook everything back up. Plus you'll see how well the raw water pump is working.
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