Smarty pants, I really could use your help! 350 Mag trouble SOLVED?? MAJOR UPDATE

dalek

Wildboating said:

I am not convinced it is actually fixed.  I am joining them later today for the next test ride.  I am convinced that they have picked up where everyone else left off and they are just throwing parts at the problem and saying they found the issues.  Nothing you just mentioned is any of the symptoms.  

I was just about to say:-
Call me a miserable skeptic doom-monger , but I think your guys thought they had fixed it but have not. The suggested fault just does not seem to fit your symptoms. I would be happy to be proved wrong. 

Wildboating

Me too dalek.  Im increasing becoming concerned.  Im not a certified merc mechanic, but i am not idiot either.   The boat has had 100% of everything removed last winter, no water, and very little fuel.  22p props and they say they seen 4400 rpm.   Rpms should be higher, now if the base timing really was way off then maybe.  I checked the index of the distrubutor as well as others had an i know it was correct.  If all of a sudden we really can adjust base timing on a 555 motor then this is past everything i learned here from you guys.

Wildboating

Telling me water is spraying into the combustion process diluting the fuel from a cracked exhaust manifold does not add up.

Wildboating

Leaving work heading there, can get nothing done right now.  I feel they are throwing parts at this again.

Dream_Inn

Good luck Wild!  We are all keeping our fingers crossed that this is all fixed and the resolution is known.  thanks for keeping us updated! I feel we are all in this one together!

dalek

Wildboating said:

Telling me water is spraying into the combustion process diluting the fuel from a cracked exhaust manifold does not add up.

I concur entirely.

212rowboat

orange is lean, plain and simple.  not talking rust (which is caked), but almost like an orange powder coat.  engines just over stoich will do this- like, between 14.9 and 15:1 will start doing it.  they'll turn bright white if it's really lean. 

i could SO see a hairline in the exhaust water jacket causing this.  it makes sense.  

we were looking at fuel charge and suspecting the charge wasn't right.  we figured you were running lean because of something with the fuel system- either faulty injectors, faulty pressure, or an obstruction.  but the system checked out.

i kept talking about un-metered air, such as a vacuum leak or valve seals or valve timing.  i kept going back to timing of valve train/crank position as it will impact both the dynamic compression of the engine as well as have a direct impact on the ignition timing map.  but that checked out.  

a hairline crack in the exhaust water jackets makes perfect sense in retrospect.  it 'steams' as it enters the passage- and that pressure is greater than the exhaust pulse's.  it would flow with it to a point, but when it reaches a certain point it would create a barrier the exhaust pulse is unable to breech.  the steam entering the cylinder past an open exhaust valve is introducing more o2 into the cylinder, which throws your air:fuel ratio lean- hence orange plugs.  when the pressure is beyond that the engine's exhaust pulse can breech, it would behave precisely like an obstructed exhaust pipe- a catalytic converter clogged on a vehicle- an exhaust flap stuck in the passage not allowing but some pressure/volume past- and the engine won't rev beyond that limit.  

so the question now is the condition of your valves and seats, pushrods and springs.  excessive back pressure, which is what this amounts to (in addition to extra o2 from the steam) will tulip valves, bend push rods, weaken valve springs, make a mockery of valve seats, and wear on seals.  

davidbrooks

OK you guys just took this from a Masters Level course on Engine diagnostics to a doctoral thesis.  My head hurts.  Does it haul **** or not?

Wildboating

I’m here, testing soon but i am skeptical yet hopeful. 

Wildboating

Everyone you talk to has a different story, they are not used to having someone half a slight clue.  Tried telling me they adjusted base timing but when I called that out it changed to they indexed the distributor.  When I asked what was wrong they said we just verified it was right.  Supposedly the 4400 rpm runs were pre finding cracked manifold and replacing. All my enthusiasm is gone.  Just another shop swapping parts and calling it good. 

Wildboating

Went for test run, seemed much better than before but I noticed it would bog after idling trying to raise rpm.  Noticed a vibration in boat so shut motors down then restarted to isolate which was running rough.  Starboard will not restart.  Seems hydrolocked. 

212rowboat

don't force it.  no need in bending or breaking anything... you can pull a plug or two and see if it spits at you when you turn it slowly. 

do you have dry or wet joint manifolds?  wet have more opportunity for dripping into the cylinders.  dry has to defeat gravity first. 

Wildboating

Limping back on one. Not sure but think wet

212rowboat

the elbow in the picture is on the riser on dry joint... it's missing on the wet joint manifolds pictured below. 

212rowboat

actually, it doesn't matter... my bad... 

the crack or leak is internal to the manifold and it isn't going to care about joints.  the crack, if high on the plenum, can impact all the cylinders not just one such as if it's cracked low on a particular runner...

Wildboating

Water is out, engine restarted.  Merc told them to pull exhaust manifold and riser and pressure test combo now. 

Wildboating

It was the same manifold they replaced that hydrolocked.  Never happened before so interesting to see what went wrong. 

212rowboat

That is a place where torque specs are crucial... Dry threads, incrementally tightened.  

Black_Diamond

Missing exhaust shutters I bet.

Wildboating

Shutters are in tact and functioning 

Wildboating

I’m leaning to the riser on top of the manifold is actually what was cracked not the manifold.  Taking apart and putting back together opened it further. 

212rowboat

you'd think marine engines, which have those heavy water filled cast iron manifolds hanging off four small bolts and relying on shear strength alone to hold them and the risers flat against the heads port would do something better to support them... larger bolts or some sort of slip in where the weight is held by a shelf instead of relying solely on clamping of (again) four small bolts... i'm not that experienced i'll readily admit, but... it seems every failure i've seen on a manifold is early in it's life, and adjacent cylinder two- otherwise, they rust out at the ports on wet joints at the junction of the riser.  dry joints just don't have these issues until they're long in the tooth- IF they make it past a hundred or so hours- which you'd discover a busted manifold due to bad head marriage before that mark...

note to those installing manifolds- use as thin and strong a gasket as you can find while getting a good clean seal/seat, dry threads while torquing them, and afterwards pay particular attention to area around cylinders one and two.  before i windowed the block of a 305 bored to 314 i had a leak there- the cylinder ingested a good amount of water, and blew apart a wrist joint and journal- with the the rod seeking (and finding) daylight with reckless abandon.  those walls were thin i admit- i wouldn't rec anyone bore a hapless 305 out that far and expect life (i didn't for the record) especially when 350 cores are everywhere just as cheap... but if i hadn't ignored the leak or recognized it for what it was i'd still be running that engine.  

never would i have thought that situation and this one were related.  

when that engine was losing it's life, it would lock on starter right after shut down (trying to restart), but a few seconds later it would turn fine.  water evaporated... with a cool rested engine, it would do the same, but i could coax it to turn by pulling the coil wire (no threat of truly starting) and pushing it out.. meaning, not much water... until there was... and when that finally happened? it sounded like a rock concert in some perverse foreign tongue i'm unfamiliar with.  all it took was that once.  i should have fixed it, but... then i wouldn't have the fire breathing 357 i'm running now (with fully closed cooling, 1.6 rockers and cam dialed in to perfection matching the card at each point, base timing advanced to 14.5* w/o a hint of ping running 98octane rec racing fuel, port matched intake and exhaust, and likely 325hp and puking torque that's going to make short work of the SEI alpha one clone dangling off its rear-end whether it's 'hardened' or not, a 55k coil on plugs indexed and gapped to 060)... it's the game we play.. well, it's the game i play anyway. 

those four bolts... such oversight in my humble opinion... at least use hardened studs, right?   

Black_Diamond

Bolted joints is a study all unto itself. In short, you never want bolts in shear, only tension n. The clamping forces when properly torqued are all you need/want. A huge fail is using the wrong grade fastener for the application, swapping in grade 5 or 8’s from say 3’s thinking you are improving the situation is actually incorrect. Higher grade fasteners require higher torques to get the proper stretch of the fastener. You can easily exceed the material strength of the bolted parts before getting the torque / bolt stretch. Then you end up with a loose joint: with leaks or fasteners in shear and they break. 

My engineering seminar for the evening. lol

212rowboat

hehehehehee- nice, @Black_Diamond!!!!  and TRUFE!!!

my personal failure was considering the mighty remflex gasket and using them.  they are 'fantastical' for road engines- headers in particular, that don't weigh a lot and are further supported by junctions at the collector.  remflex's are magic, especially with headers that aren't perfectly flat.  they are thick and pliable at first, but harden after use.  you actually squeeze them into the shape required to seal the marriage.  after several heating cycles they're hard as brick.  you gotta get them right the first time.  in addition to remflex, i also use STAGE eight bolts for clamping power... those are some great tools for the purpose of exhaust clamping.  check them out if you're not familiar with them.  they can't be used on marine manifolds- far too short.  

but to your comment, yup- the right fastener is everything... 

Wildboating

They still do not know why the motor hydrolocked.   Merc suggested manifold cracked due to low water flow from impellers.   They are due to be replaced at beginning of this year which I told them to just go ahead and do them.  They did not find anything looking at the riser and manifold.  Reassembling and retesting.  Not sure i love this idea, seems like we are headed for another hydrolock....

212rowboat

The only thing I dont like about pressure testing is that it doesnt tell you about expansion under heat.  There could be a crack there that only bleeds when it expands, or a floating surface at the head or the riser. ****, it could be a bad intake manifold gasket, and if you're running vortec heads its even more likely that is allowing the water jacket to weep onto the chamber...  Those are fairly easy to spot if you yank the intake manifold off... They usually leave signs of passage .

Wildboating

Intake manifold is my next to check.  As several of you have pointed out the symptoms seem to follow unmetered air intake.   Im meeting with shop tomorrow. I want them to go with me on the boat and explain two identical motors, two identical exhaust systems, two identical drives and why the port motor sounds lite and spins freely and the starboard sounds deep and restricted.   I keeps saying let the boat tells us whats wrong, if we listen to it you can hear it, plus from dead stop a small amount of equal throttle the sync dives to the port until we get up in rpms.

Dude_Himself

Working on bikes: I used to have a flowmeter that you'd stick in the intake and it would meter/measure the airflow. German thing. That would and the difference between engines. My money is still on ignition, but unmetered air makes some sense too.

dalek

Wildboating said:

Intake manifold is my next to check.  As several of you have pointed out the symptoms seem to follow unmetered air intake.   Im meeting with shop tomorrow. I want them to go with me on the boat and explain two identical motors, two identical exhaust systems, two identical drives and why the port motor sounds lite and spins freely and the starboard sounds deep and restricted.   I keeps saying let the boat tells us whats wrong, if we listen to it you can hear it, plus from dead stop a small amount of equal throttle the sync dives to the port until we get up in rpms.

You have a boat with two engines. Instruments show nominally the same fuel use for each engine.  One engine produces a lot less power than the other.

The above statement must be wrong.

Energy in equals energy out. It matters nothing what motors you have or what is wrong with them. They cannot cheat the laws of thermodynamics. If the energy is going into that starboard engine, it is coming out somehow. If the same fuel and air are going in, the energy is either coming out as mechanical power or going down the exhaust, as unburnt fuel, or into the water as heat. I would argue this is undeniable.
I would suggest you concentrate your thoughts on:-
Is the energy really going in?
If so, where is it going?
Also, I would suggest, as all the plugs are uniform, that the fault must either be in the centreline of the engine, cam or crank, or the electrical system, as these are the only other things common to all cylinders. Possibly the connection between the them.
I am no expert on this particular engine, so feel free to call me out on any errors in my thinking.

Black_Diamond

You can get the manifolds checked for cracks by mag particle inspection.