70bs Mercuiser 165 hp inline 6 Water in oil

I have a 70's era fiber gl

I have a 70's era fiber glass boat. There is water getting in the oil. It started getting in there slowing a first but now seems to be getting worse. The motor has 1100 hours on it. The Person who I bought it from claimes its a 5L 165Hp liter inline 6 (I think its a 4.1?). I suspect the water is coming from the intake manifold gasket. Maybe head gasket...
Would replacing these fix my problem? or are these motors known for worse problems like cracked head or manifold??

Any help would be great!
Thanks
Larry

"Well it`s a great motor and i

"Well it`s a great motor and if it hasnt been severy overheated it will be long lasting.
manifold life is about 6 years, pull it and check for water intrusion at the intake ports.next pull the head and check the head gasket, look very carefully at the top front of #1 cylinder wall, the area where the circ pump sits in front. sometimes the block rots thru there."

"Bt Doctur is right on the mon

"Bt Doctur is right on the money. Those motors are prone to water leaking into the 1st cylinder. I have your exact motor in my boat. My block cracked a couple years back so I purchased a used one off ebay, which turned out to have the 1st cylinder obliterated by water leaking into it. I just combined the two motors to make a working one. When it was in the shop being rebuilt a Merc bulletin was put out that said to fix the problem, just advance the timing. I dont remember how much though. So there's never any confusion my mechanic made a mark on the engine to keep the timing set at that point. You might want to check that bulletin out once you get your motor fixed. Do you know if the motor was winterized last fall? When did you purchase it? It could be a cracked block. Hopefully its just a gasket. Good luck. If you need anything, I've got a whole bunch of extra parts."