BACKGROUND: I have an Azure 20' deck boat with Volvo Penta 5.0 GXI-G V8. Its dry weight is around 3900 lbs. I have been having some performance problems with the boat when I have the boat loaded down with people (not so much with one or two people on board, but when I have 5-6 adults on board I have a hard time getting it to even plane). I have changed fuel filter, distributor cap, rotor, and plugs. I talked to a mechanic and he recommended checking fuel pressure and doing a compression test on the cylinders. The fuel pressure was a steady 50-52psi. I then did a compression test which showed some concerns, but as I explain further you will see why. I did the compression test this past weekend after opening up the boat which had been sitting outdoors for the winter. This prior fall/winter I winterized the boat and fogged the engine, but I did not get a chance to change the oil. So here is a list of what I did:

Added about 6oz of Seafoam to oil
Started engine for about 1-2 minutes to get seafoam and oil mixed and flowing in engine.
Engine made some valve noise, but not horrible.
Turned off engine
Removed plugs and did compression test on all cylinders. Number ranged from 105psi to 135psi.
Plugs looked normal but maybe had a film of oil on them (from winterizing fogging most likely)
Installed plugs and ran engine for about 15 minutes
While engine was running I sprayed into the engine throttle body a full can of "Seafoam Cleaner and Lube"
Turned off engine and waited about 20 minutes
Started engine again and ran for another 10 minutes
Turned off engine and pumped out oil

As I pumped out the oil and realized that their was a lot of oil in the pan _ I removed just under 9 quarts!!!

The consistency of the old oil is like water (very thin viscosity). It is a standard brown (dirty oil color) with NO "milkyness" to it. It does not smell like gas at all, but instead just like old oil should smell.

My thought is that there could be a crack somewhere in the block that is adding lake water to the oil??? Shouldn't it look white and milky? I have not taken a few drops and put it onto a hot plate to see if it creates steam yet, but I plan to do that tonight. That should tell me if it has water in it.

I added some new oil back to the engine ( 3qt of 20w50, 1.5qt of 10w40, and 1qt of Lucas Oil for a total of 5.5qts). I did this because I wanted something thicker in the engine that I could run for a short time to observe performance and then drain to see if there is any viscosity change to the oil due to water (or whatever) getting in again.

Oh, I did run the engine for a short time and then rechecked the compression. This time all the numbers where much better (105-115psi).

Any ideas on:
(1)what could make the oil so thin?
(2)why would i have almost 2.5 extra quarts of oil/mix in the pan
(3)suggestions for determining what could cause performance issues

Thanks for your help!!!!