Sad story really (but could have been much worse...). As a result of some overheating problems I was having back in Jan (6mths ago), I nearly junked my engine...
While cruising around sightseeing recently, I put the engine into reverse and it started running rough. Not TOO bad but enough that the wife even commented that it didn't sound right. Headed back to the ramp and boat was a little hard to start when putting it on the trailer. Thought to myself that it's probably due for a service.
Tried to run it when I got home, but the engine just went "clunk" then wouldn't turn over anymore. Quickly checked the oil and it was a "chocolate milkshake" and over-filled to about 2/3rds to 1/2 way up the dip stick. Water in the oil!! Checked the oil filer and it was all through the top as well. No doubt I've got water in the cylinder and Hydro Locked the engine.
Thought it's probably due to a corroded manifold/riser, as the boat's about 10 yrs old and they have never been done (or even checked! Engine's in good cond and only done 240hrs) - In fact, at the last service I told the mechanic and he said he'd pull them out at the "next service" just to check them. As luck would have it that "next service" was due last month (just my luck to miss it by 1 month).
Also thought potentially maybe a head gasket (the usual suspect in a car) as I had three overheating incidents back in Jan until I found the cause (see http://www.smwebhead.com/phpBB3/viewtopic.php?f=11&t=13715 thread) - but I think the Merc has cast iron heads (not alloy), so hopefully not...
Quick ring around and the verbal diagnosis was the same everywhere. With that much water in the oil and Hydro Lock, engine likely to be trashed. No reconditioned/rebuilt Merc's (for a Bravo1) available locally, and new engine is likely to be about 18k-20k Aus Bills fitted.
Eventually found a local mechanic (Avante) who had just pulled and traded-in a 2010 5.0LMPI (for Bravo1) from a boat who's owner wanted to re-power with a bigger engine, they'd checked it and replaced manifolds/risers/pumps belts etc and said they'd do me a deal (about 6k bills + fitting) - but they would "of course" check my engine out first (I thought what's the chance they'll say my engine's OK when they have a engine they want to sell me...).
To their credit, they called me back in a couple of days and said my motor's repairable. Looks like what had happened was that one of the exhaust flappers was burnt out (obviously when the engine had been overheating 6 mths ago) and must have let water back up the exhaust (obviously when I went in reverse), which then filled the engine with a belly-full of water and eventually caused the hydrolock (fortunately not while underway but only on the starter). They checked compression and all OK. Valves & everything else seem OK. They were going to pressure test the manifolds/Risers - but I suggested they should be replaced anyway as I'd got 10yrs out of them. Replaced oil (3 times to get all the water out). Overall a MUCH cheaper outcome than I was first expecting.
Everything seems to be running fine again now. I guess time will tell if it's going to cause any other ongoing issues (any suggestions on what to look out for?)
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