fsttyms1

Ok, i have a skiboat. It has a chevy 350 with vortec heads, and a Holley 650 carb. Last summer i noticed the motor had a slight miss/rough spot under load between idle and maybe 1500 rpm. After looking at the carb and timing and every thing being normal and running right with them i started to notice the oil getting milky. Well upon inspection the intake mani bolts were hand tight. I took the intake off, pulled the heads had them checked to see if they were warped and they were fine. I replaced all the head gaskets/intake gaskets and the boat ran great (actually better than it ever did after timing it) continued to run great all summer. Well while winterizing it i noticed the new oil became milky again. Pulled the heads off again replaced all gaskets and head bolts first thing out of storage for the winter and it ran great till today. Oil became milky again..

Any ideas as to what is going on as to why it runs great for a while and then out of no where it just acts up? Wouldn't it just do it from the start if it were a crack in the block or a warped head??

The Dougler

iTrader: (1)

possible crack in your exhaust risers?

The Dougler

iTrader: (1)

also, check the iboats.com forum, Don S is the guy to talk to re. marine engines.

Costco

I was going to say, check the heads to see if they're flat within spec but you know better....

The Dougler

iTrader: (1)

I'm stickin' with bad risers. How old is the engine? what's the drive config?

teranfon

How is your engine cooled? Is it a closed system (heat exchanger), or is it cooled via a flow-through system? Boat engines are finicky, and it's not entirely uncommon for the engine oil to become a milky white sometimes. Not being aware of your boat, I'm assuming the the water used for cooling is pushed through the exhaust manifolds. This is most common on all boats. Sometimes lake water pushes back through the exhaust manifolds and cause the system to over pressurize, resulting in water entering the engine. This may indeed be why sometimes you notice a milky white appearance in the oil at various times rather than continuously.

If your heads were checked and were true and magnafluxed, I wouldn't worry about them. Same as your intake. Has the engine ever been rebuilt before? Let me know the history before we get into clearances.

When you run the boat, is it difficult to start?

Let me know the above first before we go any further. I'm not much of a power boat guy, but a friend did have me look at his boat once because of intermittent contamination of lake water in the oil. I traced it back to the exhaust manifolds.


Terry

I hate cars

Is this a regular Vortec 350 as used in pre-LS3 trucks over the years? Does it use it's own self contained coolant with a heat exchanger?

My knowledge of boats is not that great. A girl I dated had a 5.0 Vortech that spun counter clockwise instead of clockwise. I thought that was weird.

With that out of the way, is it using a noticable amount of coolant (if applicable)? If it uses antifreeze, don't use it as it will eat the bearings just from sitting.

Are the spark plugs super clean or normal?

You had the heads checked for flatness, what about the intake manifold? It's somewhat common for the intake to not sit all the way down after the heads are surfaced during a rebuild. It can bottom out on the block instead of the heads. The cheapest cure is to double up on your intake manifold gaskets.

There's always a cracked cylinder or head which should show up as a super clean spark plug.

Intake mani could be cracked and leaking internally too which would explain the loose bolts.

Does it have an oil cooler?

Any other coolant warmed parts such as the carb?

Exhaust mani?

There are several other things but the place to start is the spark plugs. That will determine if it's going through the combustion chamber or getting in there some other way.

Bdog

I found this on a marine forum, maybe it will help

"The primary consideration for aftermarket exhaust systems are, of course, increased exhaust scavenging. But just as important is to dump the water into the exhaust as far down stream as possible, and to be sure the outlet is significantly below the top of the riser portion. Longer duration cams have a lot more reversion at low rpm, and with stock manifolds, they will suck water back into the engine. If you have an unexplained problem with the oil turning milky, this could be your problem. If you are building a replacement for a freeze-cracked engine, there is a high probability that the manifolds are junk too, so why not solve two problems at once?"

fsttyms1

The boat is a 2003. Its a inboard 2 speed trans (forward reverse) with shaft drive. The risers?
This is the best pic i have of the motor and risers


Its cooled by lake water, the pump continuously draws in lake water to cool. It has never overheated. The thing is is it will be completely normal engine oil (for 2 months now and all of a sudden it starts to hesitate while taking off an now its milky, not just a little bit but a lot.
The heads where checked for being warped, the motor has "not" been rebuilt. There are something like 450 hours on it. As for starting it after having been run, sometimes you have to choke it and give it throttle but it starts just fine after doing so.

I hate cars

Is it safe to say you get the hesitation EVERYTIME the oil gets milky? Sparkplugs will tell the tale.

The Dougler

iTrader: (1)

I'd pressure check the exhaust, you might have a pinhole leak in the risers. This would leak back down into the combustion chamber and probably drip down past the rings.

there's some good info on this link.

http://www.yachtsurvey.com/exhaust_risers.htm

fsttyms1

As for what 350? im not sure, all i know is the boat is a 2003 350 with vortec heads and holley 350 carb.

No coolant, just a lake water system. Spark plugs seem normal.

Havent had the intake mani checked. The heads havent been resurfaced, and there is a gap between the intake and block when sitting on the heads. The intake manifold gaskets are 3/16+ thick plastic and rubber, cant double them up (that im aware of).

I know water is getting into the cyl, 1 cyl the valve has like a pitting type of buildup on it from water im guessing. I will say that the first time i replaced the head gaskets after maybe 30 hrs i noticed that the head bolts on/near the cyl that had the buildup on the valve were loose. I replaced them the 2nd time to make sure the bolts weren't stretching/stretched and causing a problem. The new bolts all have sealant on them like they should.

valve with spots






Milky



The troubled boat

fsttyms1

Yes. Spark plugs though never looked bad or super clean, they just looked normal from the best of my recollection?

fsttyms1

Ill see if there is a way i can pressure test them from that link

Though my only question is why does it work normal for so long then act up? There are probably 20+ hours on it this year since i redid it and it was perfect up until today????

fsttyms1

The head with the pitting valve goes with the 2nd engine pic with the black cyl if i remember correctly?

The Dougler

iTrader: (1)

not that you need this, but never hurts.

http://www.4shared.com/file/11935363...Manual_31.html

Since it's a direct drive maybe the exhaust shutter(s) are pooched.

Also I notice in the pics on your plug wires it says indmar, which means the manual I just linked won't be perfect.

fsttyms1

Yea, its a Indmar 310

The Dougler

iTrader: (1)

I'd repost this thread on Iboats, the guys there know marine systems inside and out they've likely dealt with similar.

teranfon

From the pictures you've posted, I still think it's exhaust manifold related. Your engine isn't that much different than an automotive type engine except for reverse rotation and the addition of a specific cooling apparatus. This apparatus includes engine cooling involving the exhaust manifolds. I've seen this before on my friend's boat after he wanted me to look at it.

Personally, I would fill the crankcase with a light oil and crank it a few times while disabling it to make sure it won't fire and then drain. Then address the manifolds, specifically the risers to make sure water isn't seeping into them. Again, this appears to be an intermittent problem, which definitely seems consistent with an exhaust manifold/riser problem. At this point I very much doubt the bottom end is damaged, but observe your oil pressure once the engine is back together and running.

Check out the following info:

http://www.brighthub.com/engineering...les/66540.aspx


Terry

teranfon

I can't really comment with any accuracy unless I've seen the heads and reciprocating mass firsthand, but the photos don't look that bad. I'd be more concerned about the bottom end. Any pitting on the valves would be more harmful around the inside edge where it makes contact with the seat. While the engine was running, was there any apparent knocking and/or loss in oil pressure? Keep in mind that you will not observe and bluish/grayish exhaust smoke because the engine doesn't have any antifreeze in it. I guess it's still somewhat of a risk putting heads back on the engine, only to find you need to turn your crank and replace the main bearings.


Terry

fsttyms1

I have noticed the oil pressure dropping lower lately but that has been intermittent as well. There has been no knocking from the motor. I brought it home late last night and will flush the oil out then look at the risers and take updated pics (the pics posted were last time i had it apart)

dallison

can water be getting in from the air filter or vacuum hose???

fsttyms1

No, those are all away from water

KaMLuNg

iTrader: (5)

sorry to get OT but Kris, you tow the boat with the TL?

fsttyms1

it has happened. I usually use the expedition.

teranfon

Send me some pics if you can. I really doubt the water was related to the cylinder heads and/or block. Still seems plausible that water was pushed back into the exhaust manifolds.

Flushing the bottom end with a little diesel fuel wouldn't hurt either. The fluctuation in oil pressure may have been caused by the engine labouring or decreasing in revolution once water was introduced through the exhaust valves.



Terry

I hate cars

Water in the oil will raise the hot oil pressure. Even in my oil pressure challenged Buick, I ended up with 90psi hot oil pressure one time after a severely blown headgasket. After a while it became one of the first indicators of a blown headgasket. Sometimes I noticed that even after you change the oil it may be slightly higher than normal unil the following change.

fsttyms1

Im tearing into it as we speak. Ill get pics soon. The oil pressure is usually around 60 or so shortly before the oil got milky it was running 40 wide open and at idle it was 15 ish and actually caused the low oil pressure warning on the screen on the dash.

fsttyms1

why would mine have dropped lower ???

KaMLuNg

iTrader: (5)

i was gonna say with 350k+ mi... that is impressive..

fsttyms1

Dont forget a 6 speed and type-s motor.

fsttyms1

The gasket was wet and black so im assuming this is where it was leaking?






When i pulled the manifold off (in 1 piece) there was water/moisture in the head where the exhaust mani bolted up



The spark plugs

The 2 center ones were wet (as marked)

teranfon

Sorry Kris, but as mentioned earlier, I think water was entering via your exhaust manifold. If the oil pressure dropped that dramatically as well, I would be leery of not doing a full rebuild on the engine. Or at least having the clearances checked on the mains. The last thing you want to do is get it back together for the second time and find the engine still not performing correctly.

At this point, I'd probably contact a shop that specializes in marine engines to solicit their opinion.


Terry

fsttyms1

The thing about the oil pressure is it has done that on occasion since the day i bought it. Its always fluctuated. Never a rime or reason though.

Any one know the differences internally other than the cam for marine engines vs auto? Im thinking a fresh build in the fall (if i can get it to work temporarily) is in order and will probably make it a 383 stroker?

I hate cars

That's kind of what I was getting at in my post about the oil pressure. You may have been in a state of water contamination for a while and not known it until it got bad. Or in other words you don't have a good baseline of what the pressure should be with no water in the oil.

Chances are the bearings and rings are hurt but you may want to check the pressure relief valve and the sending unit. That milkshake can cause all kinds of problems with close tolerance items.

fsttyms1

I pulled the sending unit off the motor and cleaned it. When i stopped running it the motor was still running smooth and quiet. Im hoping i can patch it together for the rest of the season. It looks like the issue was the riser gasket, but i wont know till i get it all back together and running. I will (if it makes it that long) yank it out and do a full rebuild in the fall and replace every thing.

I hate cars

If it's not making any noises, it will probably hold up a little longer. Just keep in mind at this point you could probably throw a set of bearings, rings, and a hone and call it a day. Run it longer and you increase the liklihood of damaging other parts.

You may want to go one grade higher with the oil until pressure becomes acceptable again. I've always found the high end oils (straight weights that qualify as multi-weights) hold up better when you're nursing a sick engine and I've done a lot of that.

fsttyms1

Yea, all i really want to do is keep it together the rest of the summer if possible. Then in the fall when i put the the boat away im going to yank the motor and rebuild it.
Im already running 15w40. You think i should go higher?

teranfon

Internally, I don't know. I imagine such things as valve overlap is shortened to prevent what has happened here, and I think marine engines are built towards high torque applications, but as for that I don't know what the precise differences are.

How many hours are on the engine?




Terry

fsttyms1

The thing is a stump puller last summer i pulled out 11 slalom skiers at once, with the ability to probably get another 2 out

Roughly 420 hours