1987 3.0L water in oil

[Ypt14flyr]

Need advice. Bought this Four Winns w/ 3.0 Merc I/O and evidence of water in oil. I'm a good engine mechanic but no experience in Marine engines. We've done extensive reading on this engine and there are no exterior cracks anywhere, in the 'well known' places. We replaced impeller in out-drive, changed engine oil, and test run. 1st go-around, Found rear core plug blown out, so pulled engine and fixed that. Engine back in boat, test run then took to river. Engine froze up after about 10 Min. Back to shop, pulled engine, removed head. Found no obvious (water to oil) passages in head gasket. (Possible blow thru between #2 / #3 cyls but prior compression was tolerable ie: 155, 135, 155, 155, so head gasket not problem. (and no signs of rust on top of pistons). Leak checked manifold as best we could, cold, and no leaks found. Head and manifold intake ports show some rust in one pair mainly.. And here also, no visible signs of cracks.. but again we don't think this has anything to do with water in oil. (Maybe chasing 2 problems?)..
We did find substantial 'other' damage inside. All rod bearings toasted so badly they melted. The mains look OK. All 4 rods now junk also. Pistons look OK.
Original question / problem. We do see some rust at bottom of cylinder bore(s) (2), and have read that these blocks can crack 'inside'. We saw one video showing crack at this location. We need to find a way to check the block inside. It's now completely bare. I guess we just need to plug all 'holes' and blow in air and do the soapy water trick?
Trying to decide if this thing is worth fixing. Crank is bad at rod journals also. We had the head 'serviced' and have all the gaskets to rebuild but now we may be holding the bag?. Advice please.

 

[Bt Doctur]

water thru the intake manifold? manifold cracked.
exaust and intake ports in head 3, 4 cyl. rusty,
head gasket blown between the 2 cylinders
whats your location?

 

[Lou C]

You def had a blown HG and that could be the source of water in the oil, I also see evidence of water leaking to the bottom of the exhaust passage in the exhaust manifold. If you have a good auto machine shop that will do a marine engine let them magnaflux the block & cyl head. Then they can measure the cyl bores etc & decide if it’s worth rebuilding.

 

[Scott Danforth]

if you are running over 4600 RPM for a length of time, you can warp the head.

 

[kenny nunez]

Usually there is a pinhole near the rear of the block on the bottom of the water jacket. That is the thinnest part of the casting. If you have an engine stand fill the water jacket with water then blow air under the jacket area and you will probably find the leak.

 

[Bondo]

Trying to decide if this thing is worth fixing. Crank is bad at rod journals also.

Ayuh,...... Welcome Aboard,...... It'll be cheaper, easier, 'n quicker to find a good running take-out motor from or in a rotten hulled donor boat,.....

 

[Ypt14flyr]

I'd like to believe the water in oil prob is 'just' the head gasket, but I'm seeing no evidence of blow thru between any of the passages in the head gasket, the head, or the block. (Although the head gasket is the 'crappy' metal one I've been warned about). Am I missing something? I poured some lacquer thinner in the rear water jacket area, near what appears to be a large scratch, and see no leak thru, but just a start. There is a band of rust in the #3 and #4 cylinder walls below the piston area that looks suspicious, but again can't find any cracks.

 

[Lou C]

maybe there....
What did the underside of the cyl head look like in that spot, is the block deck and cyl head flat and level when measured with a straight edge and feeler gauges (less than .003 variation?)

 

[cyclops222]

Warped head ? DIY damage during last overhaul.
Abused engine all the way. No confidence on parts used or installed correctly. AS Jonny Cash asked. How high was the water momma ?

 

[Ypt14flyr]

I saw that and suspected that area.. but as I mentioned the compressions were 155, 135, 155, 155 and so no real evidence of blow by between those 2 cylinders.. (#2 and #3 would have to drop the same, and prob below 100 Lb).. and that wouldn't have anything to do with water in the oil anyway, would it?.
I bit the bullet and took the block to the best engine builder in this area for cleaning and Magnaflux. Can't wait to hear if he finds a crack. He did point out a couple areas in block to suspect, (In general with this engine type), but no real signs of rust in those areas, so crossed fingers. But if block isn't cracked that would just leave another mystery, unless we are left to 'assume' the head gasket was leaking water to oil somehow. Need to find the actual source of this problem. Any more comments are welcome.
(I already had the head rebuilt and it's sitting at the ready. Hope I didn't jump the gun). Also bought a new head gasket that looks like a much better product. Sierra brand. Apparently these 3.0L blocks are scarce, and I still might have to find a complete engine, or at least a another block, depending on the outcome, but thanks all for your input.

 

[cyclops222]

I have had air bubbles in the radiator after the engine fully warmed up. None with room temperature startup.

 

[Ypt14flyr]

Radiator??
I'm also trying to understand if the manifold is cracked, (It contains only water, intake gasses and exhaust), how would water leaking thru a crack in manifold get in to the oil? The only places it could go is to the exhaust ports, (which would blow it all out the back), or to the intake ports, which DO show some rust, but no signs at all of water on top of the pistons.? There are no oil passages in the manifold, right?. (Only in the head., which isn't cracked). Is it possible some of the water only 'recently' (in the life of this motor), got into the intakes and thru the combustion chamber(s), then in to the oil (leaving no evidence on the pistons or the top ends of the cylinder walls?) Seems unlikely to me.. but what do I know. . Back to square one.. I'm left to think that the ONLY possibility is the block being cracked..(?) (and for that I have to wait 2 weeks for answer). There is some rust straight down from the carb mounting boss, inside the manifold, (carb exposed to the weather somehow?, But again wouldn't cause water in oil).

I hope someone out there knows this mystery. Thanks in advance

 

[2004 searay]

lets not forget the 1st repair was a blown out core plufg on the back of hte block, this indicates freeze damage. you very well have a crack in an unvisible area of the block or head. as suggested, hve the machine shop check it for cracks.
as for bondos suggestion, yeah a lake boat engine would be the easiest solution but these days, finding a good 3.0 marine engine under 3 grand is something you dont come across often, here in the east cost that is.
you have a lot of replacement parts needed and you had beetter know what cousedthe problem before rebuilding and sinking all that money into a rebuild otherwise your liable to be back at square one with all new internals.

 

[ScottinAZ]

if your manifold or riser cracks, water will get into the oil through the valves... I had a bad riser on my 2.5, and sure enough, it backed up into the valves through manifold. Thankfully it did no damage, as I caught it early (during rebuild, so on the hose). keep in mind there is water still in the water jackets after a shutdown, so it WILL find its way through either a bad riser gasket or crack while the boat is sitting.

since you have rust in the intake side of your manifold, that is kind of a smoking gun as to how the water got into the oil...

 

[Ypt14flyr]

2004 SeaRay: I agree and that's were I'm leaning. Block in the shop, and actually I may have found a guy who can sell me a block or core engine, (with crack guarantee, of course).
and ScottinAZ: Forgive me but that still confuses me. As I outlined in my last post, If I am seeing all this correctly. a cracked riser or bad riser gasket would only 'mix' water and exhaust, so the only valves the water could reach is the exhaust valves, right? If that's true 1) the 'mix' would get 'blown' out the back, anyway, (?) and 2) I see no evidence of any water at or near my exhaust ports in the head or the manifold, only the intake ports... BUT, you may have struck on something else, (that I hadn't thought of), about water sitting in the manifold after shut-down.. That might explain the rust at the intake ports in both the head and manifold, if the manifold is cracked at an intake port area, Yeah! My optimism meter just shot up to 7.. I can get a manifold and that's a heck of a lot easier than a block.. Now I gotta go dig out my four leaf clover!.. but there's still the pesky fact that my rear core plug had been blown out also... wah.. wah.. Maybe both are toast. Thanks both guys, for your input.. Much appreciated.

 

[Scott Danforth]

if the core plug was pushed out, the motor went thru a thermal-declination material breach..........the block and manifold are busted.

 

[Ypt14flyr]

A "Thermal Declination material breech".. now THERE'S a $20 phrase.. sounds awful.. lol.. you mean the SOB froze..?
Yeah I'm coming to that conclusion. The thought of trying to find a decent (un-frozen) motor will be tricky. The $1000 question is.. Is it possible for the rear 2" core plug to 'fall' out without damaging any other part of the block?.. (Please tell me it's possible... lol ).. I actually DID read one article someplace, that that plug can come out on it's own. (Vibration?).. I find it hard to believe, but looking for something to help me sleep one more night before the engine shop gives me the bad news.

 

[Scott Danforth]

Is it possible for the rear 2" core plug to 'fall' out without damaging any other part of the block?..

no

 

[cyclops222]

ALL the water sitting in that metal block cooled down at the same >>>RATE>>> at the same>>>TIMES. Damage could be equal on all the in place expansion discs. Restarting the engine and a few full warmups and WOT runs. Could have more of them leaking or falling out.

 

[Ypt14flyr]

Cyclops, the engine is all apart (and all the other core plugs are still solid like new), and judging by the lack of other plugs being out, and no external block cracks anywhere, I'm willing to believe if this thing did 'freeze' it wasn't a 'hard' freeze.. Like my GM 350 in my '78 Silverado did in Texas many moons ago. Blew every plug in sight and split the block in 3 places.. Nothing like that here with this 3.0L.
Anyway, I won't be running at any throttle settings for a while. I do know that core plugs can come out a different times depending on location and by size. The really small ones would come out last. The rear core plug is a 2" plug..(huge), and not surprised it came out first. My concern, not being familiar with the marine engines, is where any other weak spots in the block are, and hoped to collect all the anecdotal info I can here on the forum, as to where the block tends to crack from freezing. I believe the engine shop guy I found, knows everything about this 3.0L, so I'm sure I'll hear. I'm also now fairly convinced the manifold is cracked also.. I'm beginning to look for a short block or whole engine.. I can see this train headed straight for my wallet.. lol. Thanks.

and Scott, Thanks.. I was afraid you'd say that.. lol.