Little bit of milkiness in oil

kennydalglish

So bad news today from a boat mechanic ?  Took my 2000 Rinker 232 to check a little bit of milkiness in the oil.  He hooked up his diagnostic tool and says he thinks my block is cracked and thinks it's the cause of water mixing with the oil.
He can't tell for sure since there are no outside cracks in the block.
4 - 5K to pull and rebuild the engine and replace the block if it is cracked.  Ouch.

Wanted to get some opinions on here on how I should proceed ??  Buddy seems to think its a bad head gasket.
It's a 350 MAG EFI.

Havn't even had the boat in the water yet since I bought it (other than the test drive).  

kennydalglish

In addition.  Boat ran great during the test run.  No power issues, no smoking, engine sounded fantastic.  Since I havn't had it out in the water since then what do you guys think could be the cause ?  Unfortunately I didn't notice the milkiness at the time of the test drive since it may have been there ?

PickleRick

Water could come from several places from block to head gasket to intake to heads.   Does your model have an oil cooler? If so that's another place it could be.

Going to need to pull at least intake and heads.

SeaHare

While its very likely it could be a cracked block, I would want it diagnosed first and confirm. It could certainly be a head gasket or exhaust.

Pull the heads and find out

skennelly

How was it winterized?

Grahamu

I would pull the oil cooler first and pressure test it.

YYZRC

I didn't think there was an oil cooler on a 350 MAG?  Where is it?

Grahamu

There is a cooler at this point I'm not sure if it's engine oil or steering oil if it's standard cooling, I'll check tomorrow. If it's for the steering it would not show up in the engine oil.

YYZRC

For sure there is a power steering cooler at the back of the engine. 

Grahamu

Yes there is so ignore my earlier posts. But I question how the diagnostic tool points to a cracked block. 

Pat310

Yeah kind of sketchy they want to do a motor without a visible crack and not pulling the heads..

kennydalglish

Apparently the diagnostic tool he hooked up reads historical codes from the ECU.  It showed serious overheating at one point along with low oil pressure.  I am going to visit him today to get more details before moving ahead.

Willhound

kennydalglish said:

Apparently the diagnostic tool he hooked up reads historical codes from the ECU.  It showed serious overheating at one point along with low oil pressure.  I am going to visit him today to get more details before moving ahead.

That would be an indication, but could also be a head gasket if you're lucky. Compression test will help narrow it down.

kennydalglish

 It's his opinion that the block is cracked because if it was the head gasket the engine would not run so smoothly.  Anyways, he is not trying to hide anything.  We will be there when he checks out the head gasket.  Crossing fingers but preparing for the worst.  Has anyone had to have their 350 MAG EFI totally rebuilt ?  If so, what did you pay ?
 

PickleRick

Is this raw water cooled? If so I wouldnt rebuid the motor (if it's cracked you'll scrap the block any way). It's had 20 years of rust scale deterioration, even in fresh water. 

if it's a head, intake or head gasket its not too much money to get more time on the water.


 If you can find a complete new motor available thanks to covid 19 that would be my route unless they have a new block locally with a good reputation for engine builds.  Michigan motors is a well known marine engine supplier with a good reputation.

kennydalglish

Ok,  thanks for all the input guys.  Latest update.  Engine is pulled now we have a better idea of what we are looking at.  Latest theory is now water is mixing in via the exhaust intake.  Going to replace gaskets and clean up some shoddy silicone patch repairs.  Then run engine again for a few hours to determine if Oil level rises (due to water still seeping in).
Crossing my fingers that level stays steady and clean.  Will update all when we test it.

212rowboat

just a note for future searchers of things like this: 

It's been my personal experience that leaking exhaust manifolds manifest themselves early with one consistent and important indication: something that feels like hydro lock. 

if you kill your engine after running it enough to warm up, and let it sit for a few minutes- enough to cool it to where the steam settles back to water- and then try to turn it over and it acts as if the battery is weak?- but after a couple tries it turns just fine? ..... it's 99/100 times a leaking exhaust manifold. 

aero3113

212rowboat said:

just a note for future searchers of things like this: 

It's been my personal experience that leaking exhaust manifolds manifest themselves early with one consistent and important indication: something that feels like hydro lock. 

if you kill your engine after running it enough to warm up, and let it sit for a few minutes- enough to cool it to where the steam settles back to water- and then try to turn it over and it acts as if the battery is weak?- but after a couple tries it turns just fine? ..... it's 99/100 times a leaking exhaust manifold. 

I agree 100% . It happened to my port engine starboard exhaust manifold. I thought I my starter was failing. Thanks to everyone on this forum that told me to double check my manifolds, I found water in some of the cylinders. Replaced my manifolds and risers, all was good.

kennydalglish

Starting doesn't seem to be an issue but if there are cracks in the manifolds does anyone have the OEM part number ?  Its for a 2000 Mercruiser MAG 350 MPI.  Serial# 0L363645

Thanks.

stuckmoto

kennydalglish said:

Starting doesn't seem to be an issue but if there are cracks in the manifolds does anyone have the OEM part number ?  Its for a 2000 Mercruiser MAG 350 MPI.  Serial# 0L363645

Thanks.

Mercruiser 860246A15 

Grahamu

@kennydalglish. Exhaust manifold 860246A15 in stock at the Mercury Canadian warehouse.
Intake Manifold 8M0061387 not in stock expected mid July.

kennydalglish

Thanks Grahamu.  I picked up 2 today along with a new engine coupler.  I am going to have a brand new rebuilt engine when all is said and done.  Didn't start that way but it's turning out that way.

Black_Diamond

You should upgrade to the heavy duty coupler!

kennydalglish

Sorry its been awhile.  Latest update.  The exhaust manifold seems to be the root cause of water mixing with the oil.  Bought some new ones.  Also replacing a few more items while the engine is out for easy access.  Water circulating pump was leaking.  Replaced.  Also replaced Engine coupler.
Once engine is back together more testing.  Crossing my fingers we will be in the water this week.  

Liberty44140

Thats great, sounds like you got lucky that you dont need a new block! 

kennydalglish

Testing is successful.  No more water seeping into oil.  Oil level is staying steady.  
Related question since after rebuild I will be doing an oil change after about 5 hours.  What oil are people using on their Mag 350 ?  My mechanic says to use 10W-30.  Just making sure that is what is recommended ?

kennydalglish

I am located in Michigan since that has a bearing on what to use.  

YYZRC

I use 25w40. 

davidbrooks

Agree with @YYZRC i use the quicksilver 25w40. Others will chime in though on different brands. Lots of threads on here to search just on the topic of oil.

aero3113

Quicksilver 25W 40 

PickleRick

Ill be the odd ball.  Rotella 15w40 t4.  Less than 17 a gallon and you'll be hard pressed to find a better oil. I usually get it sub 14 a gallon.

It is conventional.  You can step up to t5 for full synthetic but I only use that on my vw as a band aid for a terrible design PD cam shaft that will wear quickly without full synthetic proper weight oil.

If you get a new motor run whatever warranty tells you.

Id be willing to get that quick silver/merc buys oil from another vendor like havoline, whoever gives approved oil at the best bid price.