1999 Mercruiser 454 MPI. Sucked sand into Bravo 1 last
Sunday and overheated. Shut dowm immediately. Tried to restart bu started only whined. Got towed in.

Replaced started and boat cranked no problem. Checked plugs and #2 was full of water. Cranked it out. Boat starts fine and idles fine. #2 gets 140 compresion. Haven't checked other cylinders yet, but plan to and do a leak down

Starboard flapper was in exhaust when I shut boat off last Sunday.

What kind of damage am I looking at? Cracked head, cracked manifold, head gasket? Not any of which I need right now.

Any chance I got lucky and water flowed back in from the flapper and with new plugs I am ready to go?

Probably a head gasket. How did the oil look? milkshake? how long did it run while overheating? What exhaust do you have?

Oil was OK. ran for less than 1-2 minutes. Corsa Quick and Quiet. It's running, just pops about every 10 revolution at idle, but I haven't changed sparks yet

What am I looking at for $$$?

Anybody have any thoughts?

Need more info, compression on all 8 cylinders at least.

ck your
pm on cbpba

If no. 2 cylinder held compression I would think the exhaust manifold cracked when you overheated the motor. I like the leakdown test as a first step however. If the leakdown is OK, take the elbow off the port manifold and see if there are signs of water in the manifold which indicated a crack or maybe a damaged joint between the manifold and the elbow.

Here's the latest: All cylinders test between 135 and 150. Mechanic went through his paces, all tests were good. Ran on hose, engine ran fine, oil pressure good, temps good, rev'd ok. Shut it off. No leakage anywhere. Two hours later, ran again, again everything fine, no popping, misfires nothing.

Going to water test the boat Wednesday morning see what goes then.