Bad head gasket or just water sucked up exhaust

"I posted a question about a h

"I posted a question about a hydrolocked Mercruiser 350 MAG MPI yesturday. Thanks for all the help in getting it started again. I oiled and blew out the cylinders before I started it up again without any problems.

The mechanic I've been talking to says it still is probably blown head gaskets or warped heads that caused the problem, not water up the exhaust.

I'm not sure how much of what he's telling me that I believe, so I went to AutoZone, bought a tester, checked the cylinder compression, and got the folowing results dry. They didn't seem low to me so I didn't try it with oil in the cylinders. I forgot to open the throttle up all the way as intructions said, does this mean I should start over?

2001 Mercruiser 350 MAG MPI ~90 HRS on it

Back of Engine
#4: 200 lbs #4: 198 lbs
#3: 202 lbs #3: 195 lbs
#2: 205 lbs #2: 200 lbs
#1: 210 lbs #1: 200 lbs
Front of Engine

I don't know what the pressures should be, but I read that low pressure in one or more cylinders could mean bad rings or head gasket. Are these numbers okay? And does this have any relationship at all to the possibility of the gaskets or valves being bad? Should I do any other test?

I haven't put the boat back into the water yet and have been running it on a water hose. If it was bad gaskets or valves shouldn't the water have gotten back into the cyliners again or into the oil?

It happened suddenly when the problem first occured on Friday. I overheated the engine to about 200 degrees and shut off the key while under power. When I tried to crank it would not turn over. As I said before, I found water in two of the cylinders when I got it home.

I don't know enough about engines to be certain if this guy is correct or just trying to make a quick buck on a head job.

I would appreciate any help or direction you guys can provide."

200 is not even close to Overh

200 is not even close to Overheated. You turned Off the Key while Underway? I'm Thinking Backwash into the Engine threw the Exhaust. Put it in the Water and take a Ride. Go back to Dock and check your Oil for Grey Gook. If all goes well your in the Clear. Al W.

"shutting the key off underway

"shutting the key off underway will allow water up the exaust. If you have it running and the oil is still clean then you got lucky and caught it in time. You did change the impeller ,right.?"

Thanks to both of you for your

Thanks to both of you for your reassurance.

I haven't changed the impeller yet but I do have it ordered. I'm not getting much of anything as far as water flow through the garden hose back up to the thermostat so I'm pretty sure it's what's causing the problem. I'll replace it before I head back to the lake.

Do the compression numbers look okay? Do they have any relationship to the gaskets or valves being bad?

Compression numbers are right

Compression numbers are right on the Mark. Plus or Minus 10PSI is acceptable. (Greater differentials will cause a rough Idle.)
Sears has a great little Infra Red Temp. Probe that is economical. I have one and record various areas of my boats Engine to use as a Base Line. I can usually spot little problems before they become BIG ones. Al W.

Thanks Al. I think I might hav

Thanks Al. I think I might have gotten lucky and not caused any damage. I took off the impeller pump housing last night and peices of rubber fell out of the outlet hose. (I think I've found the culprit.)I'll lake test it as soon as I get the new impeller in place and hope for the best.

"...peices of rubber fell

"...peices of rubber fell out of the outlet hose."

Assemble the pieces to make sure none are stuck in the water passages. Remove the water inlet hose at the T'stat hsg. and backflush from there before reinstalling the lower unit.