Volvo aq131a water in oil pan

We purchased houseboat with aq131a and 275 leg .this is 3rd time I had this issue I beach boat for few days then before we leave I check engine oil and I can see that engine is full of water. To top of dipstick tube .. I pumped it out took plugs out and when I cranked over there was some water that was in 3rd cylinder. How is water filling up engine? Though the exhaust to the cylinder then past rings? I'm stumped . There is a bellow with a baffle between leg and a hull is it leaking by it as its not sealing fully? Previous owner said that as long I dont beach the boat but let it float this shouldn't happen but that doesn't seam right. Water should not flow back to the engine that easy. Any ideas?

You might pull the cylinder head off and see if it is merely a bad head gasket, but chances are that the block is cracked. I believe the correct term for the condition of your engine is "toast". They sold you a pig in a poke. You were too blinded by lust to have the thing checked out by a professional surveyor before handing over your money, which would have revealed this major flaw. Now you will have to buy a new or good used engine and have it installed. Lesson learned.

Engine runs great beside that. And only takes water when parked and beached front end high . That makes me belive that ots something else . With cracked block this would happen every time .boat floated all winter in the lake and there wasn't a drop of water.

Then you should check to see if the top of the exhaust system remains below the water line with the boat beached. If that's the case, then yes there is a clear pathway for water to enter the engine. The solution is to add a loop in the exhaust routing that gets the pathway high enough. Or stay off the beach, that's much cheaper fix.

By the way boat was checked out by surveyor. And I'm a HD mech and know engines.. not much expierience with marine stuff tho. This happened only 3 time within a year of use. And and only when boat is nosed in on to the beach. That makes me believe that water is getting though the exhaust. How is engine water routed through exhaust?is it possible to fill cylinder through exhaust? Or there is a jacket that separates gases and water?

If the exhaust system is below the water line, seawater will flow in and fill the exhaust manifold. If there's any overlap, that is, where one or more exhaust valves are slightly open, then of course water will pour in past the valves and ring gap and into the sump. If you leave it long enough your boat will sink. Same deal for toilets. If the outlet pipe is below the waterline the pot will fill and flood your boat. Simple physics. Either modify the exhaust or stop running it aground. It may be that the depth aft is only a couple millimeters below the water line when you park it this way so only a very slight trickle is getting in. It's just enough to swamp your engine over the course of time you are stopped this way. Are you in tidal waters? This is probably aggravating the situation if you are. Like it is OK at high tide but as the water goes down the aft squats a little lower and the water can get in When this happens it is very important to do several oil changes with new fresh oil. You will want to run the engine up to temp, shut it off and let it cool enough to do another oil change. Repeat this three times minimum before using the boat again. If you don't you'll wipe the babbitt off the bearing shells. If you haven't been doing this, see the "toast" reference above, as your bearings are down to the copper.

As you see, if the exhaust is below the waterline, you need to have an anti-siphon loop in the system.

We are on the lake .no tides. Exhaust goes from back to the manifold straight down to 275 volvo leg. My though was to raise the engine arvbuild a raiser but I don't think I have enough room. Though a knife gate on exhaust as well but thats not super easy to do either.No way of sinking the boat it's a tri pontoon with a separate engine compartment. Top of the Engine does sit just above top of water it seams like so I think it's a ****ty design. Not much room to move it up either.i guess I could try to move it on engine mouth as high as possible.

Yeh the trouble with pontoons is not much reserve bouyancy. Again, your best option is to simply not put the bow up on the bank. I am guessing you do that to make it easy for guests to get on and off. Just nudge the bow up to the edge but don't force the bow up. Maybe a gang plank is in your future. Or a weight reduction program. Get rid of all the excess stuff you never use but have stashed around. Sometimes this can be several hundred pounds and can raise the freeboard by quite a lot. Even something like moving batteries or tankage can make a huge difference.
I think you're stuck with the engine being where it is. You can't raise it, it has to be in line with the drive. The exhaust however you can def do something about. Forget a valve that's just not even anything you should remotely consider...someone will inevitably try to start it with the valve closed plus it's a violation and your insurance company won't pay out if you do that. If you have the room, you should think about a waterlift muffler that exits over the top of the stern and has a siphon loop that's high enough that you can stop worrying about flooding the poor lump. You put a block-off plate over the exhaust port on the drive.

I like the raised exhaust idea.

Bow up = stern ( and engine) down. The top of the exhaust loop in the "elbow" is a specific height by design above the "waterline'" ( boat level or running) to avoid this. Bow up on beach artificially raises waterline aft and even though there are "no tides" there are likely wakes from passing boats.... Back in olden times, this was called "getting pooped"... Soooo , pick between a wet engine and wet guests...

There is no raiser in exhaust manifold it is the highest point

Right... it's a inline. Inline exhaust ports sit a small amount higher off keel than V engines, but the physics the same... bow up.... dunk exhaust especially from boat wakes.