1988 Sundancer 268 7.4 L overheated, sucked water into engine

Jack W. Williamson

Jack W. Williamson

Member
Nov 3, 2017
109
Syracuse, NY
Boat Info
1988 268DA Sundancer Single 454
Engines
454 7.4 L Mercruiser Alpha one
I was out on Monday in my 88268 and we heated up to 215. I immediately slowed down, then shut it down. Mechanic replaced the starter, motor turns over but won't start. He says the motor is full of water... Any thoughts?
 
Can you explain more? Did he replace the starter because of the overheating? Are you questioning whether he is being truthful with you regarding the water? But... water ingestion can happen from failing manifolds/risers and sometimes from slowing down too fast and shutting it down right away as the stern wave washes into the transom - especially if exhaust butterfly valves are missing.
 
The mechanic is a good guy. I trust him. I'm wondering if the engine needs replaced? I think the water rushed in like you said. I'm just looking for general info
 
Sounds to be hydrolocked. How old are the risers and manifolds?

Pull the plugs turn her over by hand and see if water comes out.
 
It was hydrolocked, yes. Do you think the engine is ruined, I shut it down as soon as I saw it was overheating.
 
It may or may not be toast. Hard to diagnose that one from here! :) As mentioned, pull the plugs and turn it over - start with that. But I assume you'll be having the mechanic doing this and if you trust him, I'm sure he'll figure it out. But with the limited info, honestly, we'd just be guessing. Hoping for the best for you!
 
Thanks. I will meet you know how this plays out. I feel bad about it, great boat. I will get her back on plane for sure.
Jack
 
Please get that water out quick a get the cylinders coated with some light oil to prevent further damage. Next will be compression and leakdown test.i hope you are good on those they will tell the tale. If the motor is good .overheating is next issue to solve there are many threads regarding overheating here start with the seawater pump and move forward from there . Sorry you are having problems Jack I hope it all gets back together without too much expence
 
215 is not terribly hot for that engine. You won't hurt anything at that temp other than melt whatever is laying on the exhaust manifolds. I'm betting your impeller in the lower unit is the culprit. Next time, don't panic. Bring her off plane easily and let it idle for a bit and see if she starts to cool down. If the temp continues to rise, then shut her down.

Not sure why you would need a new starter.

Also, it sounds like your butterfly's in the exhaust Y pipe are gone and allowed water up into the cylinders.

Pull the plugs, drain it down, shoot some fogging oil into the cylinders and put new plugs in it. Try to get her fired back up quickly before things start to rust.
 
Last edited:
Getaway said:
215 is not terribly hot for that engine. You won't hurt anything at that temp other than melt whatever is laying on the exhaust manifolds. I'm betting your impeller in the lower unit is the culprit. Next time, don't panic. Bring her off plane easily and let it idle for a bit and see if she starts to cool down. If the temp continues to rise, then shut her down.

Not sure why you would need a new starter.

Also, it sounds like your butterfly's in the exhaust Y pipe are gone and allowed water up into the cylinders.

Pull the plugs, drain it down, shoot some fogging oil into the cylinders and put new plugs in it. Try to get her fired back up quickly before things start to rust.
Click to expand...
Yes
 
Mine did the same thing last year. I pulled the plugs and turned it over which shot all of the water out of the cylinders. Then I put in new plugs and it fired right up. I sprayed fogging oil in the carb to coat the cylinders. The overheating did destroy my exhaust flappers which is why it hydrolocked. I had replaced the impeller and found out the reason it was overheating was the water hose from the outdrive to the transom was collapsing and not allowing enough water to pass. Runs great now, no damage.
 
"Hydrolocked" is something you need to diagnose with a compression test. The term is used for when a cylinder ingests water (incompressible) and goes in for the compression stroke (both valves closed). At that point, if there's sufficient water to "hydrolock," then you are bending either the valves or the rod. Bent valves means a head job, which isn't too bad and can be done with the block remaining in the boat. Bent rods are worse. Advice in this thread is good. Get the plugs out, inspect, then do a compression test. If that's good, then it probably didn't hydrolock.
 
wjamwhitis said:
Mine did the same thing last year. I pulled the plugs and turned it over which shot all of the water out of the cylinders. Then I put in new plugs and it fired right up. I sprayed fogging oil in the carb to coat the cylinders. The overheating did destroy my exhaust flappers which is why it hydrolocked. I had replaced the impeller and found out the reason it was overheating was the water hose from the outdrive to the transom was collapsing and not allowing enough water to pass. Runs great now, no damage.
Click to expand...
Great news. No damage = not "hydrolocked" though. Hydrolocking bends either a valve(s) or piston rod.
 
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