Water in 454 oil after possible/known freeze damage!

[CV-23]

Well......last fall I had my block/exhaust maniforlds freeze (in a quick freeze snap) and popped two freeze plugs and broke both exhaust manifolds on my 454. Thawed the block/manifolds, put in two new freeze plugs and started the engine and winterized the engine. I did leave the exhaust manifolds empty of fluids. This spring I replaced both exhaust manifolds, and fired the motor plus I changed the oil again. All ran well and now it's the end of summer and I noticed my oil level came up a bit. Pulled the oil filter and have a milkshake. Could not really see it on the dipstick? Changed the oil and filter for now but I'm sure I have a freshwater leak somewhere (raw water cooling). Standard 454 Mark IV 330hp Bravo1. Performance on the water this summer was fine and all spark plugs look fine. Should I start pulling the intake and heads off and what should I look for? What about the oil cooler? Dam plastic merCruiser freshwater pump did not even crack and I also rebuilt it while changing exhaust manifolds. fixmymercruiser gave me excellent pricing, service and shipping on merCruiser parts. Am I heading down the right rabbit hole by pulling the intake and heads? Thanks, Mike.

 

[Bt Doctur]

If your freshwater cooled (regular A/F)using a heat exchanger , the block and manifolds should not have been damaged. If only the block is freshwater cooled(regular A/F) it should not have been damaged.
Do you have the full system(motor and manifolds) or a 1/2 system(block only)
Could be a latent crack that decided to open up.

 

[CV-23]

Full raw water system.....no antifreeze, Mike.

 

[Strecker25]

Full freshwater system.....no antifreeze, Mike.

Usually when describing your system you would call it raw water cooled. Freshwater cooled is typically used to describe a closed system with a heat exchanger. just an fyi to make describing your problem clearer.

 

[CV-23]

Thanks! Updated the description, Mike.

 

[scoflaw]

What's your plan? Is your season over or would you like to boat for another month?
I'd say that motor is toast and will probably need to be replaced. or you could keep using it till it blows, might last another month.

If your season is over, you could take that motor apart and see if anything is worth salvaging

 

[CV-23]

Season pretty much over....have two other boats. I will drop a 454 mag in her if the block is cracked. 375hp would be better than the 330hp I have. Maybe a head gasket or cracked intake I hope, Mike.

 

[scoflaw]

The lifter galley on the block is the most common spot for a crack, should be obvious when you pull your intake

 

[CV-23]

Well.......drained my engine block before the freeze the other night and have oil in my water also? Looking to go with a 454 Mag
375hp or a 383 Mag/350hp. Is the Y Pipe the same or different widths for the two engines/big vs small block? Since most of my boating is not on plane, I was wondering if a small block would be more fuel efficient option? Want to stay with a carb motor. I'm watching ebay for any good candidates for a used repower. Thanks, Mike.

 

[CV-23]

Found a 454mag with 320hrs complete drop in for $2700 heading my way. I will use my new exhaust and fresh water pump. Hope the weather holds so I can get the swap done. May have to change my prop with the extra 50hp but I believe it will be fine.

 

[scoflaw]

Without knowing where the leak is, pressure test your coolers before you put them on your new motor. Would'nt toss the old engine either till the cause is found