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

212rowboat

i'm guessing those engines can be ran independently... discovering if the ratio is different is as simple as taking the boat up to the same GPS speed individually and comparing RPM's.

certainly could be the map... could be the computer- which is easy enough to exchange from side to side... but could also be the distributor/spark.  

those engines are incredibly sensitive to mechanical alignment of the shaft and engine- yeah, the engine will fire it based on the CPS, but the physical alignment has to be right- the camshaft/crank and the dizzy dropped in just right... furthermore, the caps are crap... there was a dude on another forum encountering similar issues who rebuilds distributors on the side, and has one of the countries only working SUN machines who commented he's cut plenty of them open and measured as much as 1/8" difference in length of the points.  that's crazy... it takes more energy to fire the plugs the more resistance is between the circuit (plugs/wires/cap/rotor button/dizzy position/coil) which makes it even worse as the issue 'ages'.... basically, spark is sprayed.... how does your engine know if it's spraying spark?  it doesn't... unless it knocks... and then it just knows it's knocking, it doesn't know why, but it retards the spark anyway...  then there is fuel sync involved, and what can be described as late spray instead of on the back of a hot valve spraying directly, basically, into the cylinder... the design of the vortec heads and the kidney shaped combustion chamber allows that spray to strike the spark plug, and can be evidenced by pulling the plug and witnessing one side of the insulation being darker than the other.

this fella's issue is surely interesting...  and the trip to me is that it followed into the new long block, which means, at least to me, that it just about has to be one of those components. 

raybo3

I recommended swapping drives not because of gear ratio but of a possible problem with the drive. If you get a line wrapped around your prop (and dont realize it) and put the engine in gear the prop wont spin and the engine will shut down. point is if a bearing is starting to seize up or something going on with a gear could cause the engine not going to proper RPM. Long block was change cant be much else IMO....  

212rowboat

it was just a long block..... not a turn key.... he could have easily transferred the problem to the new engine... he didn't even install new cap or rotor, or wires... i've recently had cap bad out of the box, and same with individual wires.  it happens... which makes it not only frustrating from a $$$ vantage, but the time lost in eliminating other items (time+$$$) just to ultimately return to the 'new' item later... 

Wildboating

@Michael T   I took the cover off and verified all the way thru the throttle travel the plates are opening.  Also, i verified with my Rinda Diacom the ecm is seeing an increase from 0 to 100% throttle based on throttle position on the lever.  This eliminates cable issues.  I really am thinking drive, but after everyone says this can't be i feel conflicted.  

Wildboating

@Black_Diamond  Forgot to mentioned i swapped the sensors between motors...nothing

Wildboating

Boat is getting pulled next week too fix some damage from another boater hitting me at the beach.... Another story.    Anyhow, I will repost soon as I get it back in the water.  


@Alswagg  I don't have a trailer unfortunately,  would be interested in one though!!   
Also, i wondered about swapping them at the ramp but thought it might be a crazy thought.

Weber

Wildboating said:

@Weber  I checked fuel pressure on the rail and verified it says over 40psi at any rpm or load.  Swapped fuel regulators and noticed no difference either.

PSI is one thing, volume is another.  You have a MPI system that will adjust itself for certain conditions.

When mine was scanned we assumed that the fuel  system was not the issue because of psi, but there were a few indicators that you could see something was off compared to the other motor.

I had a fuel line issue, either it was collapsing from the inside or there was something restricting the flow.  I was able to verify that by running the engine off a portable tank with a new temporary gas line.

When we first ran it on the portable tank, there did not seem to be a change, but after running for a bit the system responded to change and conditions.  Had we not continued to run we would have just assumed that was not the problem and moved on to spending more money.  Point is make sure you give these tests you do some time, the system needs to have time to make the adjustments.

Black_Diamond

Great point!  Possibly disconnecting the batteries when swapping the TMAP sensor then reconnecting too might help the FI system reset itself too (credit to Drew on this one)

Wildboating

@Weber  I wish I would have known that before hand.  I only did a short test before  I realized it was all the same.    So you u think the ECM is causing the boat to fall on its face even though the scanner does not show anything?

Weber

Wildboating said:

@Weber  I wish I would have known that before hand.  I only did a short test before  I realized it was all the same.    So you u think the ECM is causing the boat to fall on its face even though the scanner does not show anything?

It can, and no codes as it is just adjusting itself.

Black_Diamond

If not the ECM directly, the time it takes for it to refigure stuff out lime the fuel line /TMAP. 

Michael T

Yes, in fact during some of the Axius re-sets that had to be done by the area Mercruiser "super tech"  to set the "personality" of the Axius for both my 2013 EC 310 and 2014 EC 360 the system had to be shut off and we had to wait a while (he chose 10 minutes) for all residual power to drain to avoid ghosts. It takes a while for many of the electronic systems to re-set and re-configure.

Black_Diamond

Any new info on this? Went from hot to not. 

Wildboating

Unfortunately I am waiting on the local SLOWER THAN MOLASSES marina to pull the boat out.  I swear they have the most disfunction of a business.  Anything takes months to happen.  If i owned a marina in the north and had more boats work on then ability, given the short season i would be getting some new techs on.  Gotta make that money while it is hot.

Wildboating

UPDATE:   Today was the day finally, boat is out of water and we pulled the drives.  I have not been able to take a test run yet but here is what we learned.  I am told the drives are 2.20:1.   I marked the shaft and props and discovered input shaft turns 2.2 times to 1 revolution of the props.  This is the same on both.  We also discovered both turn equally easy and smooth which makes me think that the issue is not in the drives.  We visually inspected the outdrives and the gimbal housing exhaust ports for any type of restriction.  Nothing was discovered or seen on either unit.  Boat should be back in water tomorrow, i am having some body scratches repaired.  Once in i will update again with if the problem moved with swapping the drives.

Handymans342

I'm sorry you are going thru this. Very fustrating

randy56

Nothing was discovered or seen on either unit. so looks like outdrives not the problem, The guys that are working on you boat do not have an idea, to help solve mystery. 

Wildboating

Unfortunately I have had some talented guys working on the boat.  We have also done the process of elimination.  The test drive will tell me something, so it is another set of potential areas eliminated.  Good news though, when the boat was hauled discovered that the port drive hydraulic ram lost its nut, bushing and cap.  This is the second nut i had bust off, they had corroded until they came off.  Boat received a new set of nuts on the drive today.   Lucky it didnt bust the gimbal ring raising the drive with only one side~!

randy56

How could a nylon bushing SS nut come off twice? never heard of that. corroded, Like in dissipated, maybe double nut next time. If there is enough threads. You were lucky it didn't crack or break gimbal. Does that boat shop have one of those scan tools? to check for faults. 

Wildboating

I have a diacom, if you get a chance read back through my post in this thread.  You won't believe everything we have done.  So very thankful I did not bust the gimbal!

Wildboating

Randy, his was a different nut from last time.  They just reached there end life, they were dissolving in the water.

Michael T

This is one heII of a mystery. You could write a book but no one would believe it. I still think it is something "simple" like a rogue sensor or ghost code. I just hope you either find it soon or hit the right numbers on a lottery ticket. You must have put the techs kids through university by now!

Wildboating

EDITED:  In my excitement I thought the issue was fixed since we seemed to have a bit more rpm and throttles were closer together.   All said in done lasted a day, and may have not really even been any different.

Michael T

Whiskey - Tango  - Foxtrot??????

Wildboating

Honestly, I did find about a 3" by 1/4" piece of rubber in the lower drive exhaust port.  However I don't see any way possible it could have been blocking the exhaust or how it had blown out at that point. But it was there.  Also the same questionable drive has water leaking into the bellow where the drive shaft is.  Replacing bellow this winter.  So honestly, what possibly could cause this change?  This is not easy to accept, I worked to hard, too long and put to much money in for it to just work itself out because we swapped drive location. 

Wildboating

@212rowboat @Alswagg

Dream_Inn

Oh Wow!  that is really the kind of thing you gotta hate!!  You just keep wondering when it's gonna come back to haunt again.  Good luck and keep us updated.

212rowboat

Yeah... back pressure can certainly do that.  Next time you have a leaf blower in your hand, drive the nozzle into a hard surface... revs pick up but power diminishes.  It should have been apparent on the vacuum gauge, though. 

randy56

Wow, I'm happy for ya, But also understand, why you would like a better explanation, 

Wildboating

@212rowboat I understand but how could this little piece in the lower leg be causing back pressure.  I don't know.  I think the scratches on the side of the boat were causing to much drag through the air.  Lol.   Let's hope it stays working fine.