Time for replacement engine?

[mstang64bb]

I have a 1988 Sundancer with a Merc 454. It has run great all season. Today, we took the boat out with some friends for a boat ride. The boat ran well up the river, then when we got to open water I pushed on the throttle, the engine started to climb up in rpms and then the temp alarm went off. The temp ran up to 240 degrees, then all of a sudden it when back down to 140 degrees. I turned the engine off for a few minutes and tried to start it again. It would crank over but not start. I opened the engine hatch. What I found was not pleasant. There was milky oily fluid and mess all over. The engine ingested a lot of water and was puking it out through the valve cover vents.
At this point, as it's in salt water, I'm pretty sure this engine is toast. However, I'm scratching my head as to what might have happened and why. Can anyone give me as suggestions to this, and what to do to prevent it from happening again?
Thanks in advance for this sites continued support.

 

[Espos4]

As soon as possible, and even sooner if possible, change the oil and then
Remove the spark plugs, get the water out of the cylinders and spray fogging oil in them.

Then come back and post all of your maintence done over the last few years regarding manifolds, risers, thermostat, water pump(s) etc.
















Still reading this??
Put the phone down and go remove the plugs!

 

[scoflaw]

Old raw water cooled engine, right? Could be blown head gasket, cracked head from the overheat. Rusted out exhaust. If it ran good last week you could probably save it if you act quickly

 

[Loyd Dinneen]

Check your risers and the shutters if you shut the engine down fast and your shutters are shot then the back wash might have ingested into your engine.

 

[mstang64bb]

As soon as possible, and even sooner if possible, change the oil and then
Remove the spark plugs, get the water out of the cylinders and spray fogging oil in them.

Then come back and post all of your maintence done over the last few years regarding manifolds, risers, thermostat, water pump(s) etc.
















Still reading this??
Put the phone down and go remove the plugs!

Thank for your input. Boat come out today....I hope! Then, I can remove plugs, change oil. To answer your question. The manifolds and risers are 5 years old. Complete tune-up every spring (plugs, filters, oil, wires cap/rotor, Seafoam)Thermostat replaced spring from 2019, and I change the water pump every year. This year I added the brass $200 housing.

 

[El Capitan]

Next time keep it idling vs turning off to inspect. Prevent possible back flushing into cylinders.

 

[mstang64bb]

Next time keep it idling vs turning off to inspect. Prevent possible back flushing into cylinders.

Thanks for the comment. I don't know if water got into the cylinders. I also inspected the exhaust flappers at the beginning of the season, and they were good.

 

[LMBoat]

A 32 year old engine that has been saltwater cooled? If so, you are way past the expected life. I had an '84 260 that was similar. Head had rusted through the exhaust port and filled engine with salt water. The overheat may have caused the engine to leak water internally. If the engine turns over, unlikely that the cylinders are full of water. Your best be might be a long block if all the other components are newer & in good shape. Actually might be cheaper in the long run. Just my .02

 

[mstang64bb]

A 32 year old engine that has been saltwater cooled? If so, you are way past the expected life. I had an '84 260 that was similar. Head had rusted through the exhaust port and filled engine with salt water. The overheat may have caused the engine to leak water internally. If the engine turns over, unlikely that the cylinders are full of water. Your best be might be a long block if all the other components are newer & in good shape. Actually might be cheaper in the long run. Just my .02

Thank you for your comment. That is what I am looking into. I'm now trying to find a local facility that sell now or rebuilt long blocks. You're right, the components on this engine are newer and in good condition.