I have a 2005 Sundeck 220 with...

[DestinEd]

I have a 2005 Sundeck 220 with a Mercruiser 5.0L MPI.  I've had great luck with this boat and it was running great.  On Friday the 13th (ironic), I was cruising across the bay at around 3200 RPM when I noticed the power steering was stiff and 10 seconds later the overheat signal sounded.  I got it off as quickly as I could, but I guess not fast enough because I have water in cylinders on both sides.  Here is my question to anyone with experience as I suspect the heads are cracked - in this situation, do you suspect the heads, block, or both?  I can put a new set of heads on my engine but have no way to pull it out...

The source of this rather expensive problem was a $36 idler pulley just above the seawater pump!  The belt was off, and all that was left on the mounting bolt was the inner race.  The plastic pulley was melted and outer race MIA.  Suggestion to anyone with similar engine, replace this pulley and the tensioning pulley before they fail !!!

[wingless]

It would seem unlikely that operation for a very short duration w/o coolant flow would crack cast iron heads or the cast iron block.

My suggestion is to follow normal investigation steps to determine the integrity of the heads and of the block. These steps are documented all over the Interlink.

It may be that the cylinder water is unrelated, such as from a deteriorated / failed exhaust.

My suggestion is to perform a visual inspection throughout the engine room, when checking fluids, to determine if anything is amiss and to observe if fluids have leaked or parts have fallen off. This step has saved my butt several times.

Mine are always checked before and after operation, with the engines stopped and while operating.

If the engine is dead and must be yanked, then have your tow service or have the marina move the boat to the haul point to perform a proper repair.

[DestinEd]

I have been told by 2 experienced boaters that there may not be anything actually wrong with my engine now that the water is out. I've never heard of the flapper valves that are in the exhaust system before, but my neighbor had a bad flapper and swears it resulted in a similar problem. He had them changed and the mechanic confirmed it was broken completely off.

More info, see if this makes sense to someone with experience: we waited over 1 hour in waves 1-2 feet (was a bit rough). During that time there were 4 women sitting on the swim platform and 2 guys in the back near the engine - all the weight in the rear. Of course the wind moved us in all directioins (was pretty deep so didn't anchor) and my friend thinks the wave action could have pushed some water back past a defective valve. The engine didn't get past 210 I'm pretty certain, so does this sound possible? My plan is to put the plugs back in and fire it up, then check for water in the cylinders again...

[Captain_Zero]

If it overheated due to loss of water circulation. Would not cause water to crack and get in both heads. But need a bit more information. Who has made tis diagnosis. And is the engine still running

[DestinEd]

Just realized I never responded, sorry. So, I believe what happened after getting more acquainted with the boat design is this: running at high speed (25 mph) and when the overheat came on I panicked a bit and dropped the throttle and shut the engine off. The wake shoved water up into the exhaust and cylinders that had the exhaust valve open - this is because this boat doesn't have any flappers in the original design.

Knowing this could have made the fix much easier, a year later no problems and now I keep spare belts and both pullies on board with tools!!