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

Handymans342

Wildboating said:

@Alswagg

Yes, the tank was done last year and it made no difference.    What are your thoughts of the spark plug color?

The tank was done? Meaning? Sometimes you can have good fuel pressure but not enough fuel volume. 

Dude_Himself

I would say those plugs look just on the lean side, but they won't tell you as much as they would from running at WOT - then shutting down and pulling them. I would also compare them to the port engine.

I'm with Handyman - this sounds like fuel starvation (if it was ignition related I'd expect the plugs to be more fouled from unburnt fuel). And you can have great pressure with little flow - think about how a pressure washer works vs a firehose.

After testing fuel flow I'd question why: is it ECU related or supply restriction? Do the twin engines share a common fuel pickup in the tank?

Wildboating

Handymans342 said:

Wildboating said:

@Alswagg

Yes, the tank was done last year and it made no difference.    What are your thoughts of the spark plug color?

The tank was done? Meaning? Sometimes you can have good fuel pressure but not enough fuel volume. 

Alswag asked if i had eliminated the boat side fuel system, i had by running a external 5 gal fuel can as my tank.  This made no difference.  

Wildboating

Dude_Himself said:

I would say those plugs look just on the lean side, but they won't tell you as much as they would from running at WOT - then shutting down and pulling them. I would also compare them to the port engine.

I'm with Handyman - this sounds like fuel starvation (if it was ignition related I'd expect the plugs to be more fouled from unburnt fuel). And you can have great pressure with little flow - think about how a pressure washer works vs a firehose.

After testing fuel flow I'd question why: is it ECU related or supply restriction? Do the twin engines share a common fuel pickup in the tank?

These plugs show a wot run then a 1 minute cruise to the dock.  

I have others telling me that the reddish tint is water in the combustion chamber. 


As for your final question, i have swapped the ecu out so I know that it is correcty operating.  This boat has 2 tanks, i dont belive they share a common pickup.

Handymans342

How did you hook up a 5 gallon can and at what point or where did the hose connect?

Handymans342

I would say that the plug color indicates a lean condition. You should have some blackness on them.

Dude_Himself

I'm not a professional, but most of the vehicles I've owned I've purchased cheap with gremlins like this, then fixed them. I've seen reddish-brown plugs on car/motorcycle/aircraft engines as well - caused by fuel additive dye (fuel system cleaner, Stabil, etc).

Plugs with oxidation from water intrusion are a bright orange in appearance. They'll usually have some dark sludge as well - the moisture causes incomplete burn and they collect blow-by oil and fuel.

Looked at all the plugs again: I'd be happy if they came out of my engine. Compression tests are close enough as well.

I'd think it's either a near perfect or lean fuel condition at WOT, with no obvious signs of oil deposit, preignition, or detonation. That (and the tests done on the fuel) rules out fuel quality issues, and it rules out most mechanical issues (excessive blowby, timing skipping a tooth, etc.).

That would leave me with either ignition issue or fuel delivery (quantity based on pressure test) concern. I'd start with flow - it's easiest to quantify. There's always a danger playing with gasoline in a hull: keep safety gear nearby. I'd check the flow first, but if that's not definitive a quick test might be to SAFELY replumb the port fuel system past the cool-fuel module and pump to starboard engine and vice versa. If that swap the problem then I'd do the same with the ignition (or buy a spare set of wires - doesn't hurt to have them laying around) and see if that helps. I can't remember if you've tested/swapped the ignition coil and distribution yet.

Wildboating

So quick update from my mechanic.   He also pulled fuel samples from the rail, there was no water in the sample at the rail.

He ran WOT and fuel pressure actually increases over the 43 we are getting at idle.  So he is ruling out volume, if the pressure does not drop when injectors are wide open we must have volume to the pump and rail.

Wildboating

How can I see the pulse width of these injectors.  The 555 ecm does not show this info.

Handymans342

You should get that Merc engineer that helped Dream

Dream_Inn

Handymans342 said:

You should get that Merc engineer that helped Dream

Well, it took him a while on my boat as well.  I know the issue is going to be resolved soon for Wild!  I am with others on it being a fuel issue, but that's just my guess.  Although, has the ignition coil been swapped?  Cause as I mentioned, it was the same symptoms my buddy had on his 342 and it was a coil.

Wildboating

I think its time to swap the coil, but wouldnt i be running rich on the plugs if it was a coil issue?  @Dream_Inn

Dream_Inn

Wildboating said:

I think its time to swap the coil, but wouldnt i be running rich on the plugs if it was a coil issue?  @Dream_Inn

Oh man, I didn't know you hadn't swapped it yet.  Please do it just for me!  I've seen the coils do some crazy things.  & plugs do tell a lot, but it really is an easy thing to check.  I'd even move the coil wire with it.

BellevilleMXZ

That fuel pressure.....is that at wot? If it is, your volume is fine. If it was at idle you need to test it under load at a run.

Black_Diamond

This might be the longest thread on here. The most interesting to see get resolved too.  

aero3113

Do you have any fuel stabilizer in the fuel? I've seen Sta-Bil dye plugs a reddish tint.

Wildboating

I do not add any additives.  However, valvetech marine fuel does.  

Pressure is about 45 at wot. 

Wildboating

I am truly running out of things to look at.

Handymans342

You didnt answer my question

Handymans342

Handymans342 said:

How did you hook up a 5 gallon can and at what point or where did the hose connect?

Black_Diamond

I'm guessing that fuel flow/pressure was done engine not running and the pumps responding to the throttle position. I'm not sure that is representative of actual operation with the engine running loaded up. 

I had this ~exact~ problem.  Replacing the fuel lines from the tanks and both MAP sensors replaced took care of 90% of the issue.  I still have one engine that will drop rpm under load before it catches up again.  Thus my interest in this. I litterally had zero throttle response from ~1/2 to WOT when under load (mostly from idle to on plane).  

Wildboating

Handymans342 said:

Handymans342 said:

How did you hook up a 5 gallon can and at what point or where did the hose connect?

Handy, 

I took the fuel line from the output of the fuel filter and stuck it in a clean 5 gallon can.   This way i still had the boost pump and regular pump inline.


We have full fuel pressure at the rail at idle and WOT.  Is there any reason to still suspect a fuel issue?  

Handymans342

I am tapping out on this one

Wildboating

Tech is bringing me a new MAP/T sensor tomorrow.  I wish we could see data from your engines then when you had this problem.  My sensor seems to read vacuum and baro correctly.   At WOT i am .2 off of baro.

Wildboating

Im trying sensor because I am all out of options.   I will also swap out the coil.

Dream_Inn

Black_Diamond said:

This might be the longest thread on here. The most interesting to see get resolved too.  

Yeah, lots of "smarty pants" here!    I think the person that solves it should get a free prize!  Maybe a Rinker T-shirt!  I've got the coil guess. BD has the fuel line and MAP sensor. 

I need to take my boat up to WOT again one of these days.  Earlier this year,   I had one engine that was a couple hundred RPMs less than the other only at full throttle, so maybe something here can help me too!

Handymans342

Gassers. LOLOLOLOLOLOLOLOL

Dream_Inn

Did someone say something?  Nah, I think it was just a whiff of diesel!

Wildboating

New props at the beginning of this thread.   Went from 24's to 22 4x4 from hill marine.    When we swapped drives around we marked gear and prop, they were the same and it was what appeared to be 2.2 revolutions.

Wildboating

Im afraid this may not be fixable.  It is what it is.  I am going to run out of cash or sanity before we find the problem.  I feel like its all been done.   We are doing exhaust back pressure testing soon.  I wish there was a way to see the PWM of the injectors.