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

Wildboating

I sadly can't even consider it right now.  I have already replaced the long block once and 4 heads, labor, then all of these parts.  I have brand new motors.   Lets take a moment of silence and pray to the boat gods.  I am going to need them.   Not sure if they come wearing Mercruiser shirts or not. 

Wildboating

Better not be 10K.  Not even half of that.  At some point as a shop you have responsibility to address current tab.  So far all they have done is make **** worse.   I ran 3 years and 3 weekend trips flawlessly they put boat away then dropped it to start working on low rpm.  This is where i am now except it is no longer usable.

J3ff

Come up to CT with your fam, I'll show you a great time this weekend

Wildboating

Thanks J3ff

212rowboat

it could easily be a head gasket, yes.  especially floating off the deck at upper RPM's. 

the risers remain cool, but the manifold is cracking?  

can you confirm whether you have dry or wet joint exhaust?  the wet joints fill the manifold, and then water is pushed into the base of the riser through internal ports, to be pushed further into the exhaust stream after the bend.  Dry joints are readily identifiable by having little 90* passage 'elbows' from the top of the manifold to the spacer/riser external to the riser (but sometimes formed into the manifold).  

dry joint: 


wet joint:



the exhaust cooling function can be seen in this cutaway: 

this^ demonstrates a wet joint manifolds interior, and you can see the exhaust collector tower, the bosses the bolts that merge the riser to the manifold (adjacent the collector tower) and then the water passages outside those.  A 'dry' works the same, it just has the ports on either side of the 'tower' as opposed to escaping through the tower casting. 

a 'crack' in the internal exhaust runners will push water (in form of steam) out the exhaust as the pressure is greater at the head's port- UNTIL you drop that pressure. (in the form of RPM's)... then the 'steam' pressure is greater than the exhaust pulse's, and it will attempt to keep the pulse from escaping.  This is something i suggested sometime back as a possible issue you were facing- as this will cause tremendous back pressure and will absolutely limit the RPM's achievable ESPECIALLY after you've been up on plane, back down, and attempt to re-throttle. 

now when you come off plane, that 'steam' collects in the form of water this time and drains back to the lowest place, which is in the head resting on the exhaust valve seat, or, on the piston if the exhaust valve is even slightly open.  hello, hydro-lock.  that juice can't be compressed, and the cylinder winding up for the compression stroke in't going to be able to complete the rotation- pressing down on wrist joints, bearing caps, rings... trying to escape through gasket'ed surfaces, valve seats, even plug bosses.  something has to give.   

IF the breakage is close to the head's exhaust port, i would wager a guess that one cylinder will suffer more than others.  this would be evidenced by being able to 'massage' the engine to turn while you're on the water... basically, you hope to catch the engine in exhaust or intake stroke- where intake won't allow but the lessor volume of air to be ingested (because the remainder of that space is occupied with water) or the piston simply pushes the majority of the water out on the exhaust stroke.  

if the breakage is north of the center cylinders (4/6, or 3/5) the water can go where ever it wants, or equally dispense to all of them.  understand the water is actually steam and makes collecting in the head/atop the exhaust valve more likely on a cooling engine.  this is what sounds like is happening to you. 

_________________

if I were you... 

I'd remove the manifolds and scrape the surface clean with a plastic putty knife.  i'd rub it out with acetone until i could clearly see the metal mating surface, and i'd inspect it for scorching..... water will scorch that polished mating surface and tell you precisely where it's leaking IF it's due to bad mating surface and NOT a cracked manifold.  this could be due to not having a flat surface on either the heads (less likely) or the manifold (far more likely).  IF the surfaces appear uniform, free of burs or nicks, and doesn't indicate scorching (or even if it does and you've cleaned it up), I'd do this, in this order:

carefully fold blue paper towels (shop towels; they're tougher) into squares and put them in the exhaust ports.  get a can of spray gasket glue and spray the surface with a single even coat. while you're waiting for it to tack up, cut the heads off your old manifold bolts and thread them in their bosses 3/4 of the way... place the gasket on the extruding bolts and press it against the now tacky mating surface, and walk away for ten minutes.. 

upon return, remove the towels carefully as not to disturb the gasket.  now turn attention to the manifold mating surface- again clean and acetone the mating surface.  you don't have to spray this surface.  you do have to be careful as you're sliding it on the extruding bolts you threaded in, though, and as you press it against the head... then remove a single center bolt and thread in a new one in its place... hand tight + 1/2 revolution with wrench.  then the other center bolt, same thing... then outside ones always replacing the cut bolts with the new ones finger tight + 1/2 revolution with wrench... when they're all out/replaced, begin your torquing sequence.  

do the same basic concept on the riser.  make sure mating surface is clean+tacked+cut bolts+properly oriented gasket.. then seat riser on cut bolts, pull+replace one by one same way as above... four of them... properly torqued... 

make sure your 'blue plugs' on the bottom of the exhaust manifold are in and are seated to the little o ring gasket... make certain all torque specs are right.. walk away... 

come back after a day and make sure the torque specs are holding.... fire her up.  run her at moderate pace... let her cool... check specs again.  If they're still right, chances are you're good.  if you had to tighten them, keep an eye on it- even consider gong to torque spec and adding a 1/4~1/2 a revolution beyond the spec as you might have a bolt that isn't stretching as expected (so, make it stretch, but don't go bonkers). 

if you follow this procedure, and you feel good about all the mating surfaces, you're 99% likely to be able to walk away from the manifolds for 5~7 years (with proper maintenance)... if you don't feel good about a joint or a bolt, you know precisely where the issue will likely exist because you're familiar with it intimately at this point. 

it's time, my friend, you take this thing in your own hands.  if you twirl the wrenches yourself, you know more about that engine and where the issues will arise than if you don't.  it's not that i don't trust techs to do the work, it's that until i'm the one threading in a bolt and feeling grits or resistance that shouldn't be that i know and 'map' the engine's 'weak' points mentally, and go straight to them when encountering an issue.  

also.... think about this, please:

are those marine heads?  have you checked the depth of the manifold bosses?  are you bottoming out the bolts without achieving proper clamp? is there a chance something is occupying the bottom of those bosses? can you shave the length of the thread a mm or two and achieve better clamp?  

Wildboating

Dry joint

Wildboating

Wildboating

I can see the crack inside right where the water would drop inside this hole.  

212rowboat

what does cylinder 2 and 4's plug look like compared to 6 and 8?  

Wildboating

Guys came down to look myself. The water heater line that comes off the pump through water heater and back to top of plenum.  There are metal hangers that have been a tepped on and crushed down that is pinching that line off.   This line currently is not running through water heater, it is just in a loop.  Could this be causing a reduce flow to the engine that spurts at times?  I question this as these are tees off the main circuit.  

212rowboat

Nah, I've ran engines with looped heater circuit for their entire lives without issue.  Reason: it's a PITA to find pumps w/o the provision and you pay for it when you do find then. Once flow stabilizes (burps) you don't impact volume or pressure one bit so long as the system is closed...... Air in the system, however, can keep water from reaching some locations.  The highest point is the riser, which is where it will ultimately find, and fortunately that's also close to its point of departure .

pistole

I think this is getting away from the owner and he needs to reassess the work being done

Wildboating

I did manage to get some video of the mechanic working on the boat yesterday.    https://www.youtube.com/watch?v=8CSn9OlyCSc

Wildboating

😭   trying to find the humor in this 27 page saga.   Just sucks i used to have low rpm but i could go anywhere, she never left me stranded.  Now I cant leave the dock.

212rowboat

Take that thing to Cuba if you think one engine,e can get you there. Those guys down there are amazing.  A battery and a tin can, a roll of twine, and those guys can make the titantic run again if given the chance.  

Check depth of those bolt bosses.  Make sure your manifold bolts arent bottoming out.  You'd achieve torque, but not the way you'd want to... Steaming your exhaust makes all of it add up, from different tone at idle (fighting the backpressure) to decent midrange as the pulse overcomes the backpressure, just to encounter pressure the pulse can't overcome at higher rpms.  

Wildboating

I am not following on the bolt bosses, this is a term i am not familiar with.  When you get a chance can you share a photo or link?  Thank you

Black_Diamond

Basically depth of the tapped holes. 

Black_Diamond

Sure that is the crack?  Looks like a parting line from casting (where the mold halves meet). I’d think you would need a hole or substantial crack to flow water thru it against exhaust pressure. 

212rowboat

Black_Diamond said:

Sure that is the crack?  Looks like a parting line from casting (where the mold halves meet). I’d think you would need a hole or substantial crack to flow water thru it against exhaust pressure. 

I couldn't see a crack either, but figured light has a lot to do with that.  The pic is high enough quality to blow way up and look, too.  but like i said, light can play tricks in pictures. 

if there is a crack, and water has gotten in there somehow, it would most likely happen after running and attempting to start a warm engine... the steam settles, and into the heads or past an open exhaust valve into the cylinder. 

212rowboat

Black_Diamond said:

Basically depth of the tapped holes. 

Wildboating said:

I am not following on the bolt bosses, this is a term i am not familiar with.  When you get a chance can you share a photo or link?  Thank you

realize this can also happen because of debris or even fluid (such as oil some folks insist to put on threads?)... it can literally hydro-lock the bolt in that case, and... it can show perfect torque specs but have hardly any clamping power. 

if the decks on those heads has been shaved or even if you're reusing the bolts- they could have stretched just enough to slap bottom.  I'm not saying this is 'your issue', but i am suggesting it could be.  it's often overlooked. 
 

Wildboating

Black_Diamond said:

Sure that is the crack?  Looks like a parting line from casting (where the mold halves meet). I’d think you would need a hole or substantial crack to flow water thru it against exhaust pressure. 

What you are seeing is the casting seam.  The crack I believe I see is inside that hole but runs opposite of that seam. I was unable to get a good photo. 

aero3113

@212rowboat might be on to something about the bolts bottoming out. Looks like there is a lot of rust in the holes for a new manifold also. Are they using the original bolts that are streached? Also look at the top right bolt hole, is that open to water flow? looks like there is water in it? Could that be another cracked area?

Black_Diamond

Get that manifold pressure tested. 

dalek

I know it's sacrilegious, but here is a link from another forum. Probably not the same issue but interesting nonetheless.
http://www.clubsearay.com/index.php?threads/warning-brand-new-oem-merc-manifold-casting-cracks.58912/

Black_Diamond

Thread sealant / locker gets over used a lot. Can really make life hard to remove the bolts later without heat. Same for oiling threads: can let you radically over torque: use dry threads. 

Interesting link!  

Handymans342

Wow that sounds like the issue here

aero3113

You would think the mechanics doing the install would hear the cast manifold crack when they were torqueing down the bolts like on the SR post. The SR guys knew about the cracks before the boat was started again! Cast iron cracking sounds a lot different than a torque wrench clicking! (hopefully they used a torque wrench)

dalek

For what it's worth, I agree with 212Rowboat, Black_Diamond and aero3113 on this one. I just can't see lack of water cracking cast iron that fast. It doesn't even look like it's got warm. Easy enough to check length of threads and bolts.

Wildboating

I went to pickup the original exhaust manifold from the shop to pressure check it / magnaflux it.  I asked them again, you pressure checked this manifold.  Again i was told yes it is leaking.   2 major problems here, how did they pressure check the manifold if the original riser gasket is still on the manifold???   Anyone notice another problem, I sure did.  The original manifold riser gasket DOES NOT HAVE THE RESTRICTED FLOW GASKET.  Look at the new ones the are installing.   

Handymans342

Al will help