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  1. #1
    Member
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    May 2023
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    15

    New Boat - Optimax Troubleshoot

    Hey everyone, there is so much good info on the forum I decided to join. I have a new to me 2000 225HP Optimax 2.5L Ser # 0G839677 that runs like crap under way. It starts, idles and revs perfect which is why I thought it was good, should have seatrial'd but we are here now... Took it out for the first time last weekend and the first thing I notice leaving the ramp is if I punch it it stalls. Accelerating a bit slower I got on plane but motor sounded like it was dropping a cylinder intermittently and wont turn over 3K (if my RPM gauge is accurate) so I keep going with throttle mashed to see if it will clear up but after a few miles the engine started bogging, left the stick at full throttle but it bogged lower and lower down till it reached about 1200RPM. At that point I checked the fuel ball and its still hard. I back the throttle down to 1K and its runs ok, little bit of surging but doesn't sound bogged like if the throttle is up so im like "guess we are going back to the ramp at 1K"... about half way back I gun it and it jumps back to 3K but after about 15 seconds starts bogging back down to the 1200RPM range.

    This is what I have done so far, at 1K with ears, going to try and re check it on the river this weekend while its under load...
    I checked fuel pressure and I got 92 over 82 air
    I checked spark with a gap tester and it jumps 3/8 in no problem on all 6
    I pulled the air injector connectors one by one and each made the engine run rough so all 6 are firing
    Pulled the low pressure pump connector and no change
    Pulled the high pressure pump connector and it instantly stopped running (is this SUS? I feel like the LP should keep it running at idle at least)


    Compression cold is 90ish on all 6, my understanding is doing the special optimax method will yield 20% higher
    Plugs looked ok but each one had a little bit of wet oil on them - is that normal?
    Also the beeper had a wire snipped, I reconnected it and getting 4 beeps shortly after start up, I checked the oil tank and the sensor is already bypassed. That points toward TPS right? There is no engine light on the boat, I would like to add one.

    Plans...
    Check the pressure of LP pump (should be 40PSI from what I have read)
    Replace Fuel Filter in engine
    Rebuild the pulse pump (why not - its only $35)
    Test TPS if I can figure out how - can I replace on sensor at a time? I have 2 stacked. Can I disconnect one at a time? Are they redundant or dependent?
    Was thinking about pulling the VST just to check for junk- good idea? bad idea?

    What else should I check? Will post results for future reference.

    Im leaning towards fuel delivery or TPS but want to check as many things as I can.
    Last edited by 74mako; 05-25-2023 at 11:19 AM.

  2. Member
    Join Date
    Jun 2013
    Location
    LONGVIEW TEXAS
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    13,938
    #2
    no sir does not automatically point to TPS , sounds like its going into guardian mode engine needs to have faults read to determine cause of , fuel psi test at rail when problem occurs will help diagnose problem also checkout the 3.0L forum one more down for your engine
    .................................................. ...the scariest thing in life is the unknown ...................................

  3. Member
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    May 2023
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    Virginia
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    #3
    Guardian mode wouldn't bog it all the way down to 1200 would it?

    I checked the pressures with key on, engine off.

    High pressure pump is 80 and it holds 80 for awhile
    Low pressure only goes to 10psi and drops to 0 as soon as its off. Did I find my issue? Please look at the pics and tell me if I rigged the LP right.

    Still looking into the 4 beeps.
    Attached Images Attached Images

  4. Member
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    May 2023
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    Virginia
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    #4
    I think I got some bad information. Can someone confirm these are the correct pressures...

    Fuel pressure at injectors: 89 +/- 2PSI
    Air pressure: 79 +/- 2PSI
    Low pressure fuel pump: 6-9 PSI
    Lift fuel pump: 1-10 PSI

    Al long as these pressure remain consistent I don't have a fuel delivery issue right? Someone was telling me you could have the right pressure but not enough volume. I don't understand that, if you didn't have the required volume wouldn't the pressure drop?

  5. Member
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    Jun 2013
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    LONGVIEW TEXAS
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    #5
    pulse 6-9/ boost /low press elec 6-10,,,,,, 80 air /90fuel ,,,, is correct maintained through rpm range (5700) if volume to engine/ [pumps drop] pressure will drop ,run engine on a known good separate portable tank to confirm good supply
    .................................................. ...the scariest thing in life is the unknown ...................................

  6. Member
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    May 2023
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    Virginia
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    #6
    Alright guys, I need some help on this one. Today I ran on external tank, all pressures look good, no pressure drops at any rpm, I disconnected each injector while underway and each made it bog so whatever it is its affecting the engine as a whole. Runs perfectly at idle, revs fine all the way up to 2500 but under load runs like crap and will not make it past 3000. Im ready to start throwing parts, needs some suggestions. I'm thinking about starting with crank sensor. If it's not fuel what else can affect the engine under load?

    Here is a video of the engine running. Only thing was the low pressure was bouncing but i think thats from the float opening and closing. https://streamable.com/3zjz5x
    Last edited by 74mako; 06-04-2023 at 04:55 PM.

  7. Member
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    Dec 2008
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    Kents Store, VA
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    #7
    Take it to a mechanic and have them pull the codes before you start wasting $ on parts.

  8. Member
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    May 2023
    Location
    Virginia
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    #8
    I am not opposed to taking it in but I would like to try to fix it myself first, especially on older equipment I like to be able to work on it. I would like to buy a reader either but its confusing on what reader and cable I need for my engine. I looked on eBay and there is so may versions 1.0 2.0 3.0 etc. and some no cables, some with certain cables. Mine is a 2000 without the starcraft.

    The other thing is the shop here that works on Optimax isnt on the water so they can only barrel test and the engine runs perfect in a barrel. They worked on it before I bought it and replaced the tracker and diaphragm.

    I am also not opposed to having spare parts for older equipment so if it doesn't fixit and its a common part failure I am ok with having spares. The reason I was thinking crank sensor is it kinda acts like the timing is off. Idles great and I can also get it to 3K by pushing full throttle but everything in-between is bad.

  9. Member
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    #9
    Another thing I should mention is the only way to 3K is to floor it, engine will surge a few times and then jump to 3K, when it hits 3k its not sounding like its on a rev limiter its more like the engine is maxed out, I have the throttle all the way open but thats all it has, it will run 3K for a second than slowly bog it self down over a several minutes running worse and worse to under 1K even with leaving the throttle all the way up.

    I need to fish. Pls help.

  10. Member
    Join Date
    May 2011
    Location
    Spangle, WA
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    6,180
    #10
    Quote Originally Posted by bassdge View Post
    Take it to a mechanic and have them pull the codes before you start wasting $ on parts.
    +100!

    You really do need run time and fault history at minimum. Can waste a lot of time otherwise. Btw, your engine is a 3L and covered in next forum down.
    _______

    Phil
    '09 Hewescraft ProV
    '09 150 Optimax