Engine problem

arrowestarrowest Lake Cumberland (Grider Hill)Posts: 20Member ✭✭

Hello All,

I have recently purchased a 2001 340 FV and the starboard motor will not get up pass 3000 rpm! Im figuring the computer is doing this but have no idea!

Engines are 350 Mag's fuel injected! Anyone else had this issue?


Mike D



  • mvnmvn Uxbridge, OntarioPosts: 587Member, Moderator mod
    edited July 2013

    First of all, welcome to the forum and congratulations on your purchase.  There are lots of very knowledgeable and experienced Rinker owners here who will gladly offer you advice.

    There are many possible causes of your situation.  What is the service/maintenance history of the engines?  When were the fuel filters/water separators changed last?  From an ECM/PCM perspective (computer) are you getting any audible warnings?  Can you get the PCM's scanned for diagnostic trouble codes?  Do all of the pressures/temperatures look reasonable?

    Are the props the same on both drives?  Are the drive ratios both the same (stupid question, I know)?

    There will be many more offering their thoughts.....stand by.


    Good,  fast,  cheap.... pick two. 
  • Black_DiamondBlack_Diamond Holland, MichiganPosts: 4,135Member ✭✭✭✭✭
    You should be sure your tach is reading correctly, they have a bad history.  After that start with the simple things: clean spark arrestor, change gas/water and fuel filter(s), distributor cap/rotor (some can rust), spark plugs, plug wires..all pretty easy to do and gets you to a baseline.  After that you may need to get a Mercury OBD reader for the engine codes.

    2003 342FV "Black Diamond", 350 MAG MPI, 20P 4x4 Props, PC BYC, Holland, MI
  • BabyboomerBabyboomer Louisville KyPosts: 918Member, Moderator mod

    Slip 866 Sunset Marina Byrdstown Tn
  • 212rowboat212rowboat Posts: 2,065Member ✭✭✭✭✭
    I've never been a fan of throwing parts at an engine in effort to find an issue... that said, what Mark mentions doesn't fit that description as tuning is the basis of proper operation..

    you mention 'you think it's the computer'... does it run fine up until that range? it could be a simple fix, such as fuel filter in that case, because the PCM will protect the engine if it detects lean conditions...

    EFI systems rely on either Mass Air Flow (MAF) sensors or Manifold Absolute Pressure (MAP) sensors, in conjunction with Air Intake Temperature (AIT) sensors and Throttle Position Sensors (TPS) in effort to properly trim fuel and maintain near stoichiometric air:fuel ratio's.. Some (especially non-marine) sniff the exhaust (o2 Sensor) once the engine has closed loop (reached operational temperatures) and all the sensors have a baseline- then the fuel trim game is handed over to the o2 sensors almost solely... all of the mathematics and applied logic take place in the PCM, which is a good place to collect it.. :-)  .......

    you having an EFI makes trouble shooting a lot easier.. It's my position that once you take care of the 'tune' parts and pieces (which if the rig is new to you and you don't know how old or worn the parts are is a good idea), and you change the fuel filter(s), I'd get it scanned to see what codes pop (if any), and then I'd go straight to fuel trim... look for (or have the tech look for) double digit %'s in both Long Term Fuel Trim (LTFT) as well as Short Term Fuel Trim (STFT).. you'll wan to see as close to zero as you can on both.. 'Crossing Zero' is a perfect world- meaning single digit swings from (-1%) to (0%) to 1%, and back... If your LTFT is a positive % in double digits, and your STFT is single digits, don't let the tech tell you 'you're g2g', because the LT is a product of ST bumping it up.. Also, and it slays me that many techs don't even know this, the PCM is showing you "what it's doing about it" when it displays fuel trim, not a status report of where it is- so if you see a negative number expressed either LTFT or STFT, it is cutting fuel to a rich engine.. if it is Positive %, it is adding fuel to a lean engine..

    See if you can't find a diagnostic tool w/merc connectors and monitor the issue while underway..



    coupled with:

    This...  the windows based system..
  • Dream_InnDream_Inn Annapolis, MDPosts: 4,303Member, Moderator mod
    Very good writeup Drew!  Especially hit it right on about what the PCM is telling you. I will add, that if improperly winterized, the MAP sensor could've been destroyed.  (Improper fogging)

    Dream 'Inn III -- 2008 400 Express

  • MarkBMarkB OntarioPosts: 3,014Member ✭✭✭✭✭
    Check the tach. I agree mine goes wonkey on a weeky basis.

    Boat Name: King Kong

    "Boat + Water = Fun"

  • raybo3raybo3 Revere MAPosts: 3,582Moderator mod
    wonkey???? Is that a tech term....lol
    2002 342 Fiesta Vee PC Point Of Pines YC Revere MA. popyc.org
  • MarkBMarkB OntarioPosts: 3,014Member ✭✭✭✭✭
    Oh yes, wonkey in tech terms means "for no known reason, decides to act erratically, and can irritate owner."

    Boat Name: King Kong

    "Boat + Water = Fun"

  • raybo3raybo3 Revere MAPosts: 3,582Moderator mod
    Ohh LOL got it.....

    2002 342 Fiesta Vee PC Point Of Pines YC Revere MA. popyc.org
  • arrowestarrowest Lake Cumberland (Grider Hill)Posts: 20Member ✭✭

    Thanks guys for all the great info!

    I got into it a little more this weekend and have notice a loude noticeable whistle, which sounds like a vacum leak but got down close to motor and cannot find a leak anywhere! It appears to be comming from down the throttle body! Well I comparied the other motor and it does the same noise but it more short term than the problem child!

    I guess i need to just bit the bullet and purchase a scane tool so I will always have one for future problems!

    In regards to the tach not working right, Im sure it is because the boat does not have enough power to pull itself up on plain and it is eating gas like crazy!

    I had a 29 BAJA cruiser before this one with twin 350 mag carberated motors and kind of know what kind of fuel mileage I should be getting!

    I ran this boat (340) for about 3 hours at 1500 rpm average and burned up close to $250 worth of fuel!

    8-> :(
  • 212rowboat212rowboat Posts: 2,065Member ✭✭✭✭✭
    get a can of starter fluid or ether... carefully spray around the intake manifold, taking care not to aim toward the actual intake- it will rev higher when you find your huckleberry..

    but I don't think that is it.....

    I think you should get a can of throttle body cleaner, some q-tips, and a tooth brush, and clean your Idle Air Control- and your Manifold Absolute Pressure sensors.... either will ultimately trip a code, but not always... speaking of which, do you have any beeps or tone alarms with it running?
  • arrowestarrowest Lake Cumberland (Grider Hill)Posts: 20Member ✭✭

    Hello Drewactual,

    I did the throttle spray this weekend to no avail! Could not find any leaks what so ever!

    I have opted and ordered the Mercery scan tool and cable and hope this weekend I can find the problem! The lake Im on is 2.5 hours away so just running down to work on it is out of the question!

    I will keep all informed!



  • arrowestarrowest Lake Cumberland (Grider Hill)Posts: 20Member ✭✭
    By the way! No beeps or tones! Just the two when I turn the key to start!
  • 212rowboat212rowboat Posts: 2,065Member ✭✭✭✭✭
    Fuel pressure.... It's the only thing the engine can't monitor, or know that it isn't getting enough of... Mercs don't have o2 sensors in those years, which means it relies on hard tables written into the pcm to trim fuel.. trimming fuel properly has to be done with a constant fuel pressure... Meaning: at 43.5psi the duty cycle (how long the injector is open) is perfect for the rating of the injector (emerging industry standard for rating 'jectors is 43.5, but some engines operate at different pressures)... If you're hitting the 23# injector w/ 43.5psi then you're nailing it correctly.. if with less, then you're leaning the engine.. with more, you're running rich.. there is no way to sniff it with a wideband a/f gauge to know for sure.. so, you're delegated to hoping the injectors are good, and making certain the pressure is right.. i bet its a pressure drop now that I know there are no codes. Start at the filters, though.

    Take an IR heat indicator/gun with you.. when engine gets to temperature, aim it at each cylinders exterior wall where the heads meet the block, and look for big temp differences.. its a lame way to see if one cylinder leaning out.. it will be hotter... compare the readings to that of the other engine at temperature..
  • arrowestarrowest Lake Cumberland (Grider Hill)Posts: 20Member ✭✭

    Well the saga continues!

    Fuel pressure at the rail is around 24psi! Checked other motor that has no issues, same exactly so I figure that is all good!

    Hooked up Merc diagnostic tool, all clear! Only think that showed up was low oil pressure at one time, but both motors showed that!

    Did the IR gun and narrowed down to #2 cylinder and puled off injector plug, no change in motor characteristics! Checked injector continuity, all good!

    Soooooo, ran out of time so will take compression tester this weekend and check compression on #2, check for bad spark plug and for bad wire!

    I was told when I bought the boat that cap and rotor had been change but starting to wonder about that, receipts indicate port motor cap was changed!

  • 212rowboat212rowboat Posts: 2,065Member ✭✭✭✭✭
    I hope you meant 42psi?
  • Michael TMichael T Posts: 6,237Member ✭✭✭✭✭
    DAs idea of a an infared gun is a great idea. Many surveyors are now using them to look for hot spots on the blocks of engines they survey to indicate problems. The knowledgable surveyors know what to look for.  You can rent one cheaply. A quick and easy "general" check for your plugs will also tell you a lot. Too rich - black fluffy deposits, rings a problem - black oily, too hot - white scorching and damage to plug tip wilh possibly dome burned small bead marks on the insulator, just about right light gray colour. MT
  • Michael TMichael T Posts: 6,237Member ✭✭✭✭✭
    P.S. Rinker yan - I think I saw somewhere that you have diesels? Yanmars? If so, I must apologize and say my comments are for gas engines! The infared gun use still applies though and can tell you a lot about potential hot spots and heat causing restrictions. MT
  • arrowestarrowest Lake Cumberland (Grider Hill)Posts: 20Member ✭✭

    Nope Drew, its 24! Both engines read alike! When first turning the key on, it goes up to 30 then after pump shuts off it drops back to 24 and also stays there when engine starts!

    BTW I must have late 2000 because anaylizer uses the 94005 cable! I have the MEP3 ecm!

  • 212rowboat212rowboat Posts: 2,065Member ✭✭✭✭✭
    24 ain't no good, friend.. :-(

    You should see north of 40psi.. I think CSB MPI ask for 43~44 at the rail..

    the rapid loss of pressure is a good indicator of something... I'll get there in another sentence or two....

    the engine will run at that pressure, but starve in short order.. the rapid loss of pressure via a compromised (open) system you would smell quick like.. ruled out... leaves the pump and/or regulator..

    taking the plug off the injector and no noticeable difference indicates that fuel is trickling and likely either just enough to flood the injectors gate (keep it open) or not enough to squirt when it opens (delayed ignition of a/f load)...

    I'd start as the regulator if'n I was you.. I think it's mounted on the filter housing.
  • arrowestarrowest Lake Cumberland (Grider Hill)Posts: 20Member ✭✭

    Im just wondering that if both motors have fuel issues and I just dont know it because of not wanting to run it higher that the other motor because i did check fuel presure on the other and its exactly the same!

    Just read this which kindof backs up what you are saying!

    Problem has been identified and FIXED!!!!!

    What I was told is that apparently their are several fuel pressure regulators for this engine. Something about a blue line and a pink line drawn accross the regular that identifies the PSI it's designed for. In this case the fuel regulator is the one with the pink line drawn accross it; does that make any sense? Also, the coil needed to be replaced as well.

  • arrowestarrowest Lake Cumberland (Grider Hill)Posts: 20Member ✭✭
    OK......Just looked up in service manual #24 and pump presure is suppose to be 30psi!
  • 212rowboat212rowboat Posts: 2,065Member ✭✭✭✭✭
    have you pulled the fuel filter yet?   the filter being clogged could easily drop you 6psi @ idle.. it will starve the engine quick like at speed, though, if it offer that much resistance at idle speeds...

    I'd still almost bank on the regulator..

    injectors are a deep deep subject... they are rated at 43.5psi most often (FMS rates them at 39psi, and Mopar @49psi)... an injector rated at 25#'s @43.5psi will deliver just that... less at lower pressure, and more at higher pressure.. the intent of 30psi for the fuel system tells me that the injectors are pretty big on these things... a calculation that falls out of my head would make me suppose those injectors are rated in the neighborhood of 40~45#'rs (@43.5psi)... which means they spit more volume than the lesser rated injectors at the same psi and duty cycle (how long they are open).. being that they spit more volume, the demand for volume of pressure is more important than the need for higher pressure all by itself...

    so the regulator allows 30psi and quickly bleeds to 24psi?

    just for grins, break out your redneck stethoscope (long screwdriver)... put one end on the injector, another to your ear... fire the engine.. you should hear and feel click~click~click as the injectors go about their business... if you find one that sounds soft/mushy, or doesn't click? you may have found a bad injector....

    I'd guess that injector is hung open- which is disallowing pressure to hold.. and it will make that cylinder pig rich.. and pig rich will be cooler than the other cylinders (using your IR heat gun)... it will also wash the cylinders and infiltrate your oil... sniff your oil for gas.. or, compare oil on the dipstick between the two engines and see if one is a lot different in color and odor..

    the regulator is going to regulate both engines.. if both engines are dong this, then I'd aim for the regulator and see what happens.. understand, though, if those engines are on the same circuit, a stuck open injector could cause loss of pressure across both of them.. if they are individually regulated, or if they are on separate circuits, only one will suffer pressure loss due to stuck open injector. 
  • arrowestarrowest Lake Cumberland (Grider Hill)Posts: 20Member ✭✭

    OK so I am confused here!

    My service manual for this motor says that the fuel presure is 30psi! Where does the 43.5 come into play?

    Also, doesnt each motor have its own fuel pump and regulator?

  • 212rowboat212rowboat Posts: 2,065Member ✭✭✭✭✭
    disregard the 43.5psi... that is just the psi injectors are most often rated at...

    I don't know if your engines have two, or are regulated by one.. you shouldn't have a drop, though.. it should hold rock steady..

    my point being- if you have a stuck open injector, pressure will drop.. if the injector is as heavy an injector as I'm guessing it is (40#ish), it will dump a LOT of fuel.. and you're washing your cylinder.. and it will be present in the oil.
  • arrowestarrowest Lake Cumberland (Grider Hill)Posts: 20Member ✭✭
    Well Im hoping this weekend after I do the comression test on that cylinder that will clear up a lot!
  • Michael TMichael T Posts: 6,237Member ✭✭✭✭✭
    Hey DA - great plug pictures, takes me way back to the days when we adjusted the tappet clearances with step feeler gauges WITH the engines running. Everyone should note your link. Those pictures can save a lot of wasted time, troubleshooting. Nice call. MT
  • arrowestarrowest Lake Cumberland (Grider Hill)Posts: 20Member ✭✭

    Well..........................Mystery solved! Its always good to use your old instync's and apply old school motor repair on any motor!

    Compression test proved perfect, fuel was being deleveried correctly so now I'm down to figuring out why #2 spark plug is just like it was installed and I mean still bright silver on the tip and insulator is bright white!

    Hint: 1-8-4-3-6-5-7-2

    You got it! #2 and #4 where put on backwards by a reputable marine repair in the Lake Cumberland vicinity when they put new plugs in! As you know, 2 & 4 are right next to each other!

    Of course this was done before I bought it!

    Boat now runs like a champ! Thanks for all the advice!


  • raybo3raybo3 Revere MAPosts: 3,582Moderator mod
    Good find. Glad your all fixed....
    2002 342 Fiesta Vee PC Point Of Pines YC Revere MA. popyc.org
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