No head on these Mercs....I had the 2002 90hp triple for 10 years. What you see is the water jacket cover.....look closer and you will see one plate and one gasket, not 2 plates and 2 gaskets like you have on engines WITH removable heads. Retake your measurements on compression.
Engine has 3 carbs so each get's its fuel mix separately. However, the fuel delivery is such that if anybody gets any the bottom one does. With your loosing oil, I'm going to bet that you may have some piston scoring caused by the heat generated by increased friction in the cylinders. I had an OMC overheat on me once caused by a stuck shut tstat and it acted just as yours did in loosing power. It did it numerous times before I figured out that I had a problem, which got progressively worse, and fixed it......way back in my boating years and I wasn't all that knowledgeable about these engines.
120 psig is the low limit on compression per the service manual and it says "you can expect to have problems below this value". Again, the top 2 won't read 120 and the bottom absolutely nothing unless you have a bullet hole in the side of the cylinder. grin
On a problem, the oil pump is a gear pump driven by the engine crank shaft....crank turns oil gets delivered if you have any in the tank....and you said you did) and forces oil into the fuel stream at the Y hose. What did you find in your engine in the way of fuel mix? Oily gas, oil only, gas only? If your crack effected your fuel/oil delivery to the engine, you will have either oil residue (that didn't get to the engine), or you will see nothing which would attest to the fact that your engine lost power because the fuel pump was sucking (some) air and probably adequate oil with a reduced amount of gas rather than the required fuel and oil mix. Reread what I said here! No oily residue in the area, no loss of oil to the engine hence no big deal!!!!!!
1. Get a new hose and install it. Prime the oil as the service manual tells you...basically before you connect the end of the hose where the two are mixed (output of the Y), pull the sparkplugs and spin the engine with the starter till you have solid oil in the new hose Y and can see it in the fuel outlet of the hose. Then reconnect and be on your way.
2. Retake your compression just for grins.
3. Take your boat back out and test it.
4. If you want some insurance, add a pt. of your TC-W3 oil to 6 gallons of gas while you are getting things back to normal. If you use Pennzoil semi-syn. that WW sells, it won't smoke much even at double the oil ratio....assuming your oiler is working right off the bat as should be the case. That's the oil I used and loved it, priced right.
If you still have problems while on your outing, squeeze the primer bulb when the problems start to occur and see if the engine recovers. If so you have a fuel delivery problem [fuel pump, bad hose to tank, tank not venting, crud in the fuel filters (one in engine one in tank pickup)] besides the fuel delivery problem that occurred when the fuel/oil hose in the engine cracked.
Last: FIND YOURSELF ANOTHER MECHANIC! Then come back with the results.
