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

Wildboating

Would that cause a low RPM issue at higher throttle?  

Wildboating

The regulator controls that amount of flow correct?  So i have good pressure but if not enough flow due to stuck regulator I would be running out of fuel right?  This would cause a lean condition then, is this what blew my last motor???

Wildboating

All speculation of course, just shocked to find i do have this after being told by multiple mechanics i did not

Black_Diamond

You have the Gen II Cool Fuel. The Gen III is the one that had issues. 

You can have fuel pressure and poor flow. I keep thinking it is a fuel flow issue, just my .02. 

Black_Diamond

Have you swapped the ECM between engines?

212rowboat

bypass it and find out. 

that could SO be it.  running out of fuel.  

Wildboating

@212rowboat
By pass the Fuel regulator or cool fuel?  I want to be clear on what you are saying.    This cool fuel system looks like a PITA to get to or apart.  Bypassing my be much eaiser.

Wildboating

@Black_Diamond
Swapped ECM, no difference. (thankfully)

Wildboating

@Alswagg

Fuel pressure primes to about 50psi then rest at 45psi at idle.   The psi stays at or slightly above 40 psi under load.

Black_Diamond

There is nothing really to 'take apart' for the cool fuel Gen II from when I have seen.  It is just a heat exchanger.  I'd just bypass the heat exchanger part.  So basically you will have your fuel flow:

gas tank - fuel pump - regulator - injectors.

Another thought, just to rule out anything with the tank/pick-up would be to run the fuel line straight from a portable gas tank (abundant caution required).

In my everlasting curious state on this problem, I ran across this tonight:

http://forums.iboats.com/forum/engine-repair-and-maintenance/mercruiser-i-o-inboard-engines-outdrives/619428-mercruiser-mag-mpi-350-fuel-pump-s-replacement

Wildboating

@Alswagg

Will you pm me your contact info. 

Wildboating

The towel has been thrown in.  I have left a message with our resident guru Alswagg.   I am hoping that he can find the gremlin hiding in this boat.  I keep looking at other boats but I really dont want to leave this one.  This boat had everything we wanted, except a unauthorized gremlin onboard.

frenchship

Good decision, curious to find out what the gremlin was.

frenchship

By the way how many mechanics went thru your boat to trying to solve it?

Dream_Inn

I can't wait to hear what this issue is!!  (I know, you can't either)  This one is actually stressing me out thinking of what could it actually be.  Every time I think of something, I look thru the pages of responses and someone has already asked it.  I thought my issue this spring was terrible taking about 10 weeks for Mercury to figure out, this one just tops it all!!

 I will say that over the years there have been 2 342's on my dock that have had similar issues, at least to where one throttle is much further than the other to at least get on plane.  As a matter of fact, one just took his to the shop about a week ago and it was back on his lift last weekend (but I didn't see him around to ask about the fix).  I'm sure one item was changing his distributor cap since they tend to gather water on the 342s. 

Good luck and just know we are waiting and hoping this one will be figured out soon! 

Wildboating

I really appreciate it!  I cant imagine what the problem is, I hope to have some answers soon.

Wildboating

@Dream_Inn
What causes the 342's to get water in the Dist?  I have had water in mine both times we replaced it.

Black_Diamond

I've never had water in mine. Liquid form. Corrosion on the cap/rotor yes. 

Black_Diamond

Love to be at Al's shop when he runs that engine. Short drive for me too. 

Wildboating

We are starting off Tuesday with Al helping via phone with a local mechanic who really thinks he can figure it out.  However, if that fails then my season will wrap a bit earlier then planned and I will be having the boat hauled to Indiana.  I wish it wasnt so expensive to get the boat there and back before we ever start looking with AL.   Thankfully Al, has agreed to try remotely with this local tech who I really think may know his stuff.   Unfortunatley, since finding him at the beginning of the season he has been booked.   He finally decided today he was going to push some jobs around to jump in on this with us.   Everyone wants to know what it is.

Wildboating

I want to throw something else out, i have noticed with my vesselview that after i "run out" of power around the 60% mark that if i advance the throttle I will briefly see the starboard motor gain about 100 rpms then drop back to where it was.  Its like something is telling the motor to pull back.  I can do it over and over again, it briefly starts to increase rpm then drops back to around that 3600 rpm range.

Liberty44140

Wild, how many quotes have you had to haul the boat to Al? I've got a couple of local names for you to try to get an affordable haul. Also do you have a truck that can tow a 342? Wonder if you can come up with a trailer to borrow just to get it there? 

Wildboating

I do have access to a 3500 that can pull it..   ANYONE HAVE A TRAILER THEY WILL BORROW/RENT?   Liberty, I will take you up on those names also,  I want to say it was $1500 from Pittsburgh to Cleveland.  So Im figuing about the same x2 to AL and back.  This is why i reached out to ask AL about him coming here first.  Lets see how Tuesday goes with Rusty the local mechanic with support from Al.
 

Liberty44140

$1500 one way sounds very high, we are talking 250 miles tops. I'll get you some names. Also, I would look in to trailer rental from Whiskey Island and places like that....boat yards not using them right now. 

Wildboating

I want to double check the exhaust for blockage myself.  Can I separate the exhaust without replacing gaskets?  Should I pull the 4 bolts at the top of the riser to do this?   If I need new gaskets can they be sourced locally?

Dream_Inn

Wildboating said:

@Dream_Inn
What causes the 342's to get water in the Dist?  I have had water in mine both times we replaced it.

If I remember correctly, it had to do with venting that was under the seats that were directly above it.  (or maybe the vents were in a locker above it?)  I will do some chatting this weekend with a couple 342 owners & previous owners.

Black_Diamond

My 342 had no vent tubes from any of vents except the blower outputs. I added the vent tubes and at worst any water goes straight to the bilge now. 

Dream_Inn

Ok, I got feedback from my friend with his 342.  He was having identical symptoms, one throttle having to go all the way down and finally the boat just wouldn't even get on plane.  He had both distributor caps replaced, and the engine that had to go to full throttle needed a new coil.  I can't remember thru all these posts if you had changed the coil, but if not, that may be the issue.  (could always switch between engines).

Black_Diamond

Here is an interesting find (from the UK I think so pardon the wording):

symptoms were would rev to the limit in neutral but would only rev to 4200. under load,
i bought a fuel pressure testing gauge and found that it was running below pressure but would free rev to max when in neutral, so we changed the fuel pump thinking this was the problem however with new pump we still had the same problem,so we looked at the fuel pressure regulator thinking this was sticking,it turned out to be the pressure regulator has a vacuum pipe running to the throttle body just under the flash eliminator this pipe was partially block causing the regulator to allow fuel to return so we weren't getting full fuel pressure,i would try cleaning this before spending £ on a new fuel pump,
If you disconnect the rubber tube under the flash eliminator/throttle body (it just pulls off)
then give the boat a run under load see if you get full revs,if you do your pipe is blocked

Dream_Inn

Interesting.  I was playing with the regulator on someone's boat a few weeks ago and wondered about that hose and where it went (it was actually my neighbors 420 that has the paint in the fuel cooler issue - happened while he was up at Rinkervous).  Definitely a good thing to know.