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

aero3113

Easy and cheap to swap drives if it hasn't already been done.

Wildboating

Drives have been swapped. 

Wildboating

Ecm was swapped, and we verified it recognizise faults by unplugging tps last year.  The motor sounds different then port motor.  Al, I have asked to see the exhaust manifold. I will take pics of it when I stop by shop next. 

dalek

I'm right out of theories. Put a colortune plug in it. It's just a spark plug made of glass, but I guarantee it's more interesting to watch than an Adam Sandler film.

Black_Diamond

About the only parts not checked from being replaced (long block), swapped drives, swapped ECM’s, on and on are the exhaust manifolds and intake manifold.  Bad casting / defects can happen and end up with blocked passageways. 

aero3113

On my old boat I bought new risers and installed them. I could not get the starboard side to stop leaking water at one of the bolts. Tightened as much as I wanted to and still leaked. I pulled it off and it was a bad casting (big hole) that was leaking. So anything is possible!

Wildboating

The dealer boat is with is trumped,  They have no idea.  They did replace the impellers and fixed the water leak, they say the new manifold did not crack and it is good now.  We currently have the boat with no weight on it up in RPMS, higher then they have ever been ( however im still skeptical that this is due to boat being 100% emptied out and low on fuel no water).  The starboard turns 4300 rpm and port motor 4600.   They did what i asked took the boat out listening to the engine, they agree, you can hear it is unhappy and hesitant upon providing throttle.   Merc is involved and they asked me to provide a detail of what has been done to the boat, so i figured i might as well share it with you guys here as a refresher on where we started and how we ended up here.   

The former owner said he had never ran the boat WOT but knew of nothing wrong with it  When i checked the ECM readings with my Diacom software i seen the boat had never been over 4000rpms.  We had contracted for a survey,  however our surveyors report came back that both engines were in sound condition and met full operating rpms.  These rpms were not listed and when i attempted to recontact the surveryor i discovered he had suffered a fatal heart attack and passed away.  We were left to accept his survey or hire out another.  

The day the boat arrived to us at your facilty we immediately knew something was wrong.  We had trouble keeping the engines running.  A compression test revealed both port and starboard engines had tuliped valves on the number 5 cylinder.   The boat was a 1 owner from pittsburgh who was an older gentleman that ran it on the river.  I had a friend who owns a local engine repair shop rebuild both heads and put the boat back together.

Upon my first days out on the water i quickly discovered from about 60% TPS on to 100% TPS the boat would not increase RPM for the starboard motor, it seems as if it tries briefly but it immediately pulled back somehow.

In the last 2 1/2 years or trying to find this problem every shop in the area and independent mechanic each had a theory of what the problem was and we have replaced a lot of parts.   Ultimately as you know with my frustrations, all that has been done is throwing parts at it hoping something fixes it.

At the beginning of last season, the day the boat was launched and on its maiden shake down cruise i noticed something did not sound right, i promptly discovered a knock from the starboard engine and had my friend who did my head work by to assess the knock.  It was determined that I had a rod bearing that had spun.  In an attempt to save the season and also fix the low rpm issue i decided to replace the long block as a whole.  We reviewed products from many places but ultimately decided on this unit for the replacement.  https://www.perfprotech.com/new-gm-350-longblock-57l-vortec-for-years-1996-current-models-carb-tbi-mpi-w-crank-position-sensor-2541-s1/product/260508

Specifications:
• Type: 90° 5.7L V8 
• Displacement:350 cid(5736.50cc) 
• Compression Ratio: 9.4:1 
• Valve Configuration: Pushrod Actuated 
• Valve Lifters: Hydraulic Roller 
• Bore x Stroke: 4.00x 
• 3.48in(101.60x88.39mm) 
• Main Bearing Caps: 2-Bolt Cast Iron 
• Balance Method: External 
• Horsepower: 
• 295hp@5000 rpm (PFI) 
• Torque: 355 lb-ft@3600 rpm (PFI) 
• Materials: 
• Block: Cast Iron Intake Manifold: Customer Supplied 
• Firing Order: 1-8-4-3-6-5-7-2 
• Oil Pan Capacity: 5qt 
• Fuel Types: Gasoline (unleaded) 
• Engine Rotation: Clockwise (from the front) 
• Paint Protection: Component Painted 
• Shipping Weight: 500Lb 

ITEMS REPLACED OR SWAPPED BETWEEN MOTORS:

High speed fuel pump

Low pressure boost pump

water separator

8 fuel injectors

8 spark plugs 3 times

dist cap 3 times

pulled dist and re-indexed and had dist mechanically looked over

plug wires 3 times

ECM- Swapped

Ignition Coil-Swapped

MAP Sensor- Swapped

TPS swapped and verified to see 0 -99.9%

Knock Sensor- Swapped - also verified via my RInda Diacom both engines see 24* advance at WOT  

Verified engines are not in guardian mode

Swapped outdrive locations between port and starboard, visual checked for exhaust blockage at stern and through drives

BoreScoped Y pipe to verify for exhaust blockage

Checked Flappers , intact and in working order

Replaced fuel filters

Ran Starboard engine from 5 gallon can direct to low boost pump

Crossed fuel lines from port fuel tank to starboard tank and retested

Tested fuel pressure at idle, 3500 rpm and wide open throttle

Replaced 24P 3 blade b3 props with 22p 4x4 props from hill marine.  This helped get about 200 rpm

Pulled drives and verified 2.2 rotations between input shaft and prop out shaft on both drives

Fully serviced both sterns last fall, new gimbal bearings, boots, shift cables,etc

Replaced exhaust boots with Merc HP exhaust boot, i believe these bypass the lower drive boat is a bit louder now.  This was done to eliminate in potential restrictions and increase flow.

Ran both motors with flame arrestor removed

Replaced batteries

At WOT fuel pressure test last fall revealed some intermittent minimal drops in pressure.  This can be seen here. At the 1:16 mark you will start to see the fluctuations and if listening to the audio you can clearly hear the drops.  This is why i replaced the low pressure boost pump, it was discovered to electrically turn on however it would not build the 8-9psi of fuel pressure it was supposed too with the high pressure pump disconnected.  I would only get 0 psi off of it.  After replacing and discovering it did not change anything i resorted to replacing the high pressure cool fuel pump, cooler and pressure regulator.  I have not reattempted this test to see if we still get these little spikes.    https://www.youtube.com/watch?v=mWNu8drY5LA     Last i checked my Garmin GFS10 fuel sensors provided this data to the nmea 2000 system.

Starboard Motor WOT: 16.5GPH - 3600 RPM


Port Motor WOT:  18.3GPH - 4000 RPM

Wildboating

CONT:  

I was concerned that maybe this was electrical, i have captured some data to review.  I have noticed that as RPM increases there is a small amount of voltage drop however I feel it is still within the acceptable range.  I do know that RINKER has a builder disconnected the orange wire from the alternator to the main fused power input on the starter.   I have been told to reconnect it however i have not as of today.   Notice on the electrical data attachment the low voltage spike down to 12.8 range.  This correlates with some fluctuations in the engine speed and TPS sensor.  I may be chasing here but after three years and sleepless nights along side a empty wallet i have to look at all possibilities   

Here is what I have learned that the motor is trying to tell us.  The engine/exhaust on starboard engine does not sound the same as port motor.  It was this way with original engine and the new long block.  Starboard Engine sounds deep and restricted, port engine seems light, free and spins easily.  There seems to be a hesitation in the starboard motor.  All 8 plugs from starboard motor have a orangish tint, all 8 plugs form port motor have more of the greyish beige color that im used to seeing.  Same fuel and quantity delivered to both tanks at the same time every time.  

When the engine is put into gear and equal amount of throttle is applied (determine by ecm TPS) the synchronizer on the dash burries to the port motor.  Only as we get the boat up into higher rpm ranges does it begin to come back closer to sync.  I must adjust throttles to sync engines, starboard will be 60-100% and port around 40-50%.

Please see the orange tint on the 8 plugs, this was immediately after ending a 2 hour ride home at 3600 rpm.  All 8 plugs on the port motor were they aforementioned greyish beige color.  The last photo shows the comparison from port to starboard after a lengthy run, same fuel at the same time.

Last photo shows throttle position and correlating readout on vessel view screen.

I will leave it to Ivantic to provide current data screen shots as we seem to have increased rpm slightly.

IS IT POSSIBLE THAT I HAVE A DEFECTIVE INTAKE MANIFOLD?  I feel that the air turbulence around the port motor is louder than it is with the port motor.

Black_Diamond

I think, as I mentioned a bit earlier, all you have left is the intake manifold. Bad casting or a crack that opens up under engine load. 

Found this tibit too:  rusty / redish colored spark plugs combined with odd RPM behavior = lean issues.

I will say dropping to the 20P 4x4 B-III props (from original 24, then 22) helped my rpm and engine noise reduction.  

I chased this same problem, less the data you have from the Rinda!  Somewhere between rerouting gas lines, PCV valves, MAP sensor and tune ups I mostly solved it. The 20P props were the final win. 

Seems some 342’s with the 350 MAGs really perform differently than others with the same drives/props. Mine has never been a 40mph+ boat, even light loaded at WOT. Some do. Some like the 24P props, mine big not. Strange.  

Handymans342

What was the compression readings??

Black_Diamond

I believe he said they were all good. 

Handymans342

Come on Al, that's all you got? LOL

Dude_Himself

And the wiring harness Al - the possibility that there's a loose/chaffed wire that's somehow impacting performance without being noticable on the Rinda/ECM.

Handymans342

When I had a gas boat a long time back lol, the motors were not getting enough fuel. I could tell by the exhaust smell. Once I fixed the issue the boat was flawless

Wildboating

*****************************************************************

I spoke with shop yesterday and they are acknowledging the engine sounds like it is laboring and they are getting Merc in as they don't know where to go next.  They did replace the impellers and water bulb, put new exhaust manifold on and replaced plugs again (don't know why).  They tested and it did not crack the manifold this time.??   


SOOO..  I decided to take the boat out last night........  BOTH ENGINES sound exactly the same, the laboring sound was gone last night, it has never sounded like the port motor.  1/3 tank of fuel,  some accessories brought back to boat, cooler fuel of ice and beverages plus 4 adults,. we ran at 36mph at 4300 rpms with top up and side curtains in.  I was baffled, i pushed on up and i would say 4400 on starboard was topping out and 4500 on port motor.   We started this saga at 3500 rpm, made our way up to 3800-3900 and now we have 4400??  

I don't understand, how could the laboring or restricted sound just disappear.  They sync still falls to port side briefly but easily makes it way back to a synced state with a about an two or three inches of throttle separation.    The boat needs the bottom redone, its  getting pretty worn, that has to be good for 100 rpm or so i would think.  How much more am i missing?  WHAT CHANGED?  I can not go on not knowing what the problem or is after $1,000's of dollars, blood and sweat...   But She was absolutely humming and didnt sound like it was struggling to do so?    Oh and the impellers we replaced, not a single tine broken or torn..  they look as good as the ones we just put in.    

I am happy as can be but so puzzled and lost.  I hope it stays, but they are not aware of fixing anything, I am not aware. So gurus, knowing what we have known what could have worked itself out?  Could i have an electrical issue somewhere that is messing with the ignition and when they were in there working the moved something around just right and now it is firing like it should and it is no longer laboring?   They sounded exactly the same in neutral or gear.

@Alswagg
@212rowboat

Wildboating

22p props, what RPM should i call it good?    Is 4400-4500 acceptable as WOT on 22p blades and worn out bottom?

GMSLITHO

wow I see this started 2 years ago 

Wildboating

GMSLITHO said:

wow I see this started 2 years ago 

It has been a very long journey...

reneechris14

Glad to hear she running good
I have stock 22's 
05 342 350mags and I can go over 5000rpm
Well I have only once.

Handymans342

Could have been a fuel line restriction that broke loose or dissolved and is now in the filter

davidbrooks

Good bottom paint and you will get closer to 4800.  I have 22p  4 blade  Hill props and i am just under 5k at WOT.  

Black_Diamond

WOT you should be ~5,000 rpm. 

212rowboat

Do you have a spec sheet on the heads used?  

Do you run a different coil on one or are the coils of similar age?  Do me favor... Pull lazy engines coil and take pic of it from all sides. 

Sometimes the braces wear through the coating on the coil and it finds a way to ground through that breakage.  Ive seen that at least three times in my life I can recall... Is simple little thing that takes power from ignition spark, and coukd also explain the drop in voltage.  

If one of the tecs disturbed the coil it could have settled on area not worn through/scratched.  

That orange on the plugs is something to be happy about.  Its just lean of stoich. On water you'd rather be just rich of stoich and that gray color, but the rust color is fine. That could be because minor pressure/volume of fuel delivery.  I wouldn't worry about that..

Different valves, rockers, length of push rods, lash, or variance in seat angles can also cause more air delivered which means the orange engine is getting just a touch more than the gray one, and the reason I asked about heads. 

Wildboating

Drew,

You may be onto something here.  The tech swapped the coil between the motors.  I will get a good look at it.  I vaguely recall swapping the coil once before but I am not 100% on that right now.  

The heads were rebuilt originally but the new long block i posted came with new heads.

dalek

At the beginning of your problems you said you were not a seasoned mechanic. 
Well, you are now.
Hope everything stays OK.

reneechris14

Is this really the price you have to pay for an education. 

The Main Exchange

Thats good news, hope it stays running well for you.

Dude_Himself

@reneechris14 Cheaper than paying MSTI or whatever the current Marine Training Institute Tuition is. ;-)

rasbury

Awesome! So glad to hear...not sure what we are going to have interesting to read but I'm sure something will come up somewhere...we have boats.

Wildboating

My top has blown.  Whatever this shop did to the exhaust manifold has once again hydrolocked the motor again.  I really just want to give up.  I’m broken.