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  1. #1

    Default 454XL, lacks power and won't rev past 2800 RPMs

    Hello,
    I have 2 crusader 454XL, both long blocks were purchased new, the port engine works perfect, the starboard does not have any power and will not rev past 2800 RPM. it idles perfect, smooth, no misfires, no missing, no shaking, and will rev as high as you want while in neutral. but when under load it feels like its towing another boat, almost like if it had a governor that does not allow it to rev past 2800.

    Here is what I have done so far:
    New spark plugs, new wires, new distributor(EST), new coil, new fuel pump, new fuel filter and filter housing, new fuel lines and new anti syphon valve at the tank. also checked the breather and ran the engine with the gas cap off. timing is set correctly and will advance to 30 degrees at 3000RPM, (in neutral) I also replaced the carburetor with a new rebuilt unit. The transmission is a brand new ZF63A. I exchanged transmissions between the engines and the problems persists. I checked the exhaust for blockage and can't find any, the manifolds and elbows are new. I also put a vacuum gauge on it and the manifold vacuum is constant at 21, it will not drop indicating and exhaust blockage and it does not increase to suggest and intake blockage. I switched between fuel tanks and no change.The fuel is fresh, Did a compression check on the engine (twice) and all cylinders have 140psi. I am getting a rattle noise in the transmission so I replaced the damper plate with a new one and the noise continues at low RPMs, goes away after 1200 RPM (probably torsional vibration from the engine) it also shifts very hard, in comparison with the other engine. I have also check the linkage cables and they open the carburetor fully.

    The only thing I haven't changed is the alternator, which is brand new, not sure if that can cause the lack of power, it shows that its charging 14v.
    I am pretty sure that I have listed everything I have done, I have been trying to get this engine to run for about a month now and I am just out of ideas.
    I would appreciate any help I can get on this.

  2. #2

    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Wow, admire your perseverance! The big question is whether the problem is fuel or spark. Recommend checking the timing while under wayat maximum speed to ensure you are still getting about 30 degrees BTDC. Mightalso consider plumbing in a temporary fuel pressure gauge (mechanical combinationpressure/vacuum gauge type) between the fuel pump and carb to ensure you aregetting a steady 7 psi or so. Best wayto do this is to use flex fuel line and an appropriate tee and inverted flarefittings readily available at car parts stores. Are your engines configured with MSTS ? Interesting problem, please share yourprogress. Good Luck.
    FL Panhandle


  3. #3

    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Thank you
    I have not checked the timing under way. I will do so tomorrow or Tuesday, I also did not put a pressure gauge between the pump and carb, since I replaced the fuel pump for a new one, but I will do it this week also. I have a steel tube there so I guess I have to rig some kind of temporary test hose. The engines are not MSTS.
    I will post the results this week
    Once again, thank you for the input.

  4. #4
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    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Bit of confusion here....has this issue been around since the new long block went in?

    I don't see the need to recheck the timing under load as the advance is driven solely by engine rpm....ie idle or in gear shouldn't make any difference.

    Your original post mentions a vacuum gauge test but is real short on details - can you ellaborate on what was done ??

    Interesting that there is no MSTS controlling the timing - any idea when the MSTS was deleted?

  5. #5

    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Thank you Makomark, I appreciate your help.
    The problem started with the new long block. These were Brand new long blocks, Gen-6 that came with oil pan, oil, heads, valve covers, harmonic balancer and timing chain cover. All brand new, I only added the intake manifolds which I purchased new online.

    The timing issue is a little confusing to me as well. I have the telco EST distributors, (brand new)I have both engines setup the same, for some reason the base timing is 12 degrees when the timing plug is "on" but when I change it to run, the base timing jumps to 22 degrees, and advances to 30, at 3000 RPMs (on both motors), the 8 degree only advance concerns me, but the port motor runs perfect and has a lot of power and the starboard is very weak and won't rev past 2800RPMs, like I said in my previous post, it does not hesitate, or bug down like its running out of gas, but feels like a golf cart when you floor it and just does not go any faster. I see and hear the secondary on the carbs open, but it just won't rev past 2800 RPMs and the power curve to reach the 2800 is very weak, it feels like there is no power from the moment I hit the throttle.

    On the vacuum test: I connected a vacuum gauge to the port in the carburetor (quadrajet) where the vacuum pull-off of the secondary goes and I get a constant 21 PSI vacuum (the green zone of the gauge) when I accelerate fast, it goes to zero, jumps back to above 21 and then settles of 21. If I accelerate slowly to 3000 RPM(in neutral) the gauge stays constant at 21.

    As far as the MSTS, when I originally purchased the boat 10 years ago, only one motor had the MSTS unit and it was not working, so I removed it back then, and used the boat without MSTS ever since with no problems, when one of heat exchangers got damaged, I had a problem with one engine and that is why i replaced them both with the new long blocks.
    Like I said, both are set up identically, one runs perfect and the other is very weak.

    One thing I noticed, that I forgot mention is that when I removed the fuel line tube from the pump to the carb, there was zero fuel in it, and I had ran the engines the night before. I did that when I changed the fuel pump, and checked the tube to make sure it was not kinked. Not sure if that is indicative of a problem or not.

  6. #6
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    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Ok...so you really have 'new' non-standard 454's- qjets on a Gen-VI!!....based on the gear identified, I'd suspect both are standard LH rotation.

    The vacuum tests, with the added details, sound pretty normal....good thing!!

    What you see with the EST's is pretty common (though most people dont check at those points)....

    Based on your OBTW, and the other data, I'd be inclined to suspect fuel. when you check the fuel pressure, do it at idle and under load. another thing to check is the voltage available at the fuel pump....could be a simple as the relay contacts are dirty and letting the pump run but not at capacity....another known problem is the oil pressure switch that controls the fuel pump - they are known "problem children"...

    finally, did you change the fuel filter in the carb, behind the fuel inlet nut?

  7. #7

    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Actually, I am sorry, these are Gen 6 long blocks, they are Volvo Penta long blocks, 3857949, LB7.4L, roller cam and lifters, with oval ports, one piece rear main seal, 4 bolt main, both standard rotation. The carbs are Marine Quadrajets, same as the originals that I had on the previous Gen 5 454XL engines.

    I checked the voltage at the pump, and at the 10amp breaker, and both showed 13.45volts. I did that by putting the engine in gear to bypass the neutral safety switch and had someone hit the egnition while I tested the voltage at the pump. I checked all the grounds I could and they seemed ok, also took a reading at the oil pressure switch and it was the same 13.45 volts, I guess I can interchange the oil pressure switch from one engine to the other and see what happens.
    The screen fuel filter at the carb is brand new.
    I also suspected its fuel, but whats throwing me off is that I replaced the Fuel pump, which was new to being with, replaced the water separator/filter housing, the water separator and the anti syphon valve at the fuel tank. while I had the anti syphon valve out, I blew into the tank to make sure the pickup tube is not clogged up.
    I am going to connect a new fuel line directly from the tank to the engine, replacing the one I have now, even though is brand new, I want to rule out that it may be collapsing under suction.
    I am going to the boat tomorrow and I will post updates then.
    Once again, thank you for your help.

  8. #8
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    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    may not be anything with the 'new' components of your systems but with the carryover.....like the harness, relays, etc.....

    If your fuel pump voltage test was done with the key in START, it bypasses the 'normal' current path for the fuel pump....so I wouldn't deem it conclusive.

    If the boat has one tank I'd check the valves and other plumbing parts in that fuel supply subsystem. A quick way to isolate the issue would be to temporarily use an outboard can as the fuel supply to the starboard system....

  9. #9

    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    OK
    I ll check the harness, and if possible this weekend I can switch it from the good motor, I installed the old harness on both motors but I inspected and cleaned them up before I did and they looked pretty good.
    There are no relays in this system, just (1) for the ignition.
    All I have is an ignition relay, a 50 amp main breaker and a 10amp fuel pump breaker.

    No sure how else to test the voltage to the fuel pump. I am a little confused with the bypass of the normal current.

    Thank you

  10. #10
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    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    your owners manual may have the wiring diagram for the engine.....the fuel pump switch is a SPDT. it is controlled by engine oil pressure. The common terminal goes to the pump and the NC terminal is usually fed with the I terminal from the starter solenoid. The NO terminal is usually fed from the ignition....so during engine cranking, the current path to the pump is different than during engine running.

    The harness itself should be issue free is undamaged - its the connectors where 99% of the problems exist....breakers, like relays, have finite lifetimes....a voltage drop measurement on them usually reveals a bad part...

  11. #11

    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    yes, you do have a valid point. The yellow/red wire feeds the switch at the point of ignition, then the purple one is the one that feeds the pump after the engine is running.
    I think if the oil pressure switch was bad, the engine would not start, anyways that is easy for me, because I can just take the one from the port engine and switch it. I will check the connector and make sure is good. I can probably connect two wires to the positive and negative right before the pump so I can get a reading with my volt meter. I don't have enough room in that area of the engine room to put a tester while the engine is running.
    I ll let you know how it goes.
    Thank you

  12. #12

    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Well...went to the boat yesterday afternoon and did a test on the fuel pump. It has constant 13.25volts while the engine is running. the ground is good. With this I have pretty much tested or replaced the entire fuel system. So its back to square one. Like I said before, the engine does not rev to 2800 and then dies or looses RPMs, it just doesn't have any power right from the moment you throttle up, once it reaches about 2800 it stays there steady, it does not overheat, hesitate, misfire or show any signs of anything wrong, it just won't go past that level.

  13. #13
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    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Quote Originally Posted by wellcraft33 View Post
    Well...went to the boat yesterday afternoon and did a test on the fuel pump. It has constant 13.25volts while the engine is running. the ground is good. With this I have pretty much tested or replaced the entire fuel system. So its back to square one. Like I said before, the engine does not rev to 2800 and then dies or looses RPMs, it just doesn't have any power right from the moment you throttle up, once it reaches about 2800 it stays there steady, it does not overheat, hesitate, misfire or show any signs of anything wrong, it just won't go past that level.
    I read you replaced the carb. Does the new/old carb actually open up fully? Mounting gaskets can interfere with butterflies, linkage can be misadjusted, choke may not open fully, etc. Unlikely the engine runs great with WOT at 2800 rpm. Other, more remote possibility is exhaust blockage. It will result in a smooth running, very low HP motor.

  14. #14

    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Yes, thank you.
    That has all been checked, the carb opens fully and the linkage is working correctly. When I said the engine runs great, I meant it does not backfire, hesitate or miss, obviously it has no power and won't rev past 2800 so there is something definitely wrong. I checked for an exhaust blockage. I connected a vacuum gauge and the reading is constant at 21 on acceleration, If I lost vacuum slowly it would indicate blockage but It doesn't.
    I have a short video I took of the engines running, I ll see if I can link it so you guys can get a better idea of what I am looking at.

  15. #15

    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Here is a short video I took of the engines running, the starboard engine (right side ) is the one with the problem.
    https://youtu.be/2mXrzaFfOHc

  16. #16
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    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Quote Originally Posted by wellcraft33 View Post
    Yes, thank you.
    That has all been checked, the carb opens fully and the linkage is working correctly. When I said the engine runs great, I meant it does not backfire, hesitate or miss, obviously it has no power and won't rev past 2800 so there is something definitely wrong. I checked for an exhaust blockage. I connected a vacuum gauge and the reading is constant at 21 on acceleration, If I lost vacuum slowly it would indicate blockage but It doesn't.
    I have a short video I took of the engines running, I ll see if I can link it so you guys can get a better idea of what I am looking at.
    21" Hg is a HIGH vacuum reading. Certainly not one you could get at WOT. Or even at mid throttle. more like idle. Are there mufflers?

  17. #17

    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Yes there are mufflers but I checked them and they are not obstructed. Plus I think if the exhaust was obstructed, I would have a vacuum loss when I increase the RPMs, and its not happening.
    Click image for larger version. 

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    That is the vacuum gauge I am using, the reading is right between the 20 and 21 mark in the green zone, at idle and at 2000, 3000 RPM (in neutral) It is constant.
    like I said, upon sudden throttle the niddle will go to zero and then come back to like 25, then settles at around 20-21.

  18. #18
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    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    OK, sorry, I misunderstood the acceleration thing. Was thinking boat accel, you were thinking crank accel. So, idle and no load vaccum looks fine. I'd like to know what is going on at the problem area, with load, at 2800 rpm. The vacuum should approach maybe 3" and stay there. So, you visualled internals of all exhaust hosing and muffler?
    I know you said carb plates are clear. Did you eyeball all the way to the intake manifold, thru the carb at WOT/load? Obviously, I'm describing tests that require two people.

    Also, maybe i missed this. What is the other engine doing when both engines are WOT? Can it hit 3800 or more? I would say that would be normal, maybe a bit more.

  19. #19

    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Thank you diver_dave
    yes, I did have someone driving the boat and looked into the carbs, the secondaries are fully opened, I also took all the exhaust apart and stuck my hand inside the muffler, both sides, and they both seem to be good. they are very simple inside. Not sure if you saw the video I posted.
    I have not done a vacuum test with the engine underway. I guess I ll try that next time.
    The other engine is very responsive and revs up to 4500 RPMs even when its dragging the starboard one at around 2800, I can actually run the boat at about 20 knots in this condition.

  20. #20
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    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Quote Originally Posted by wellcraft33 View Post
    Thank you diver_dave
    yes, I did have someone driving the boat and looked into the carbs, the secondaries are fully opened, I also took all the exhaust apart and stuck my hand inside the muffler, both sides, and they both seem to be good. they are very simple inside. Not sure if you saw the video I posted.
    I have not done a vacuum test with the engine underway. I guess I ll try that next time.
    The other engine is very responsive and revs up to 4500 RPMs even when its dragging the starboard one at around 2800, I can actually run the boat at about 20 knots in this condition.
    private vid, no access.

    so, 4500 is what you would expect with both engines delivering full HP with the correct props. This leads me to ask; "how sure are you about the 2800 rpm reading?"

    If the 2800 is real, it seems the other engine is underpropped. 20kts, currently. Should be closer to 30? You know the healthly engine will be over redline, i'd say once you get the problem child fixed.
    I"m about out of ideas. It would be great to get fuel flow readings off the problem engine. How do the plugs look? Are you sure you don't have a couple of ign. wires reversed? 2800 would seem to be 2 or 3 cylinders are out.

    Does the prop shaft rotate normally by hand? Prop didn't change?
    Last edited by diver_dave; 08-22-2017 at 02:50 PM.

  21. #21
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    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    3" of vacuum - not until WOT....at 'cruise' - on a normal engine - you'll probably see 6"-8" at 2800 rpm.

    Does the air valve open along the way to WOT (only under load - in neutral, it will never open)?

    Like dd, seeing the vacuum readings under load, at the throttle opens, would be good data.

    Finally, even with decent voltage on the fuel pump, it would be good to verify adequate volume and pressure, especially since you noted the supply line was 'dry' after running the engine. and it wouldn't be bad to verify no restrictions on the suction side of the fuel pump either....temporarily hooking up the vacuum gauge to one of the unused ports on the fuel filter head is normally the easiest way to do this.

  22. #22

    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Thank you
    I ll check the pressure on the lines, better yet, I am going to hook up a fuel line directly to the carb to rule out any collapse of the line.
    Did you see the engine running in the video I posted?

  23. #23

    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Diver_dave,
    The boat is a wellcraft 3300 sport bridge, with the previous engines, It always rev to 4500 RPMs, cruises at 24knots( at about 3500) WOT at 4500 I can do about 30., maybe a little more. I never ran it that hard anyways.
    I am sure of the reading of 2800, it could even be less because the port engine is probably helping the bad one a little. either way, once you hear the engine running it looks a lot like a fuel restriction, I just can't seem to pinpoint it and I have replaced everything already in the fuel system.
    I am going to try a few things tomorrow and I will post the results.
    I really appreciate all the input from you guys.

  24. #24
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    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Quote Originally Posted by wellcraft33 View Post
    Diver_dave,
    The boat is a wellcraft 3300 sport bridge, with the previous engines, It always rev to 4500 RPMs, cruises at 24knots( at about 3500) WOT at 4500 I can do about 30., maybe a little more. I never ran it that hard anyways.
    I am sure of the reading of 2800, it could even be less because the port engine is probably helping the bad one a little. either way, once you hear the engine running it looks a lot like a fuel restriction, I just can't seem to pinpoint it and I have replaced everything already in the fuel system.
    I am going to try a few things tomorrow and I will post the results.
    I really appreciate all the input from you guys.
    If boat is kept in the water. LOOK at the prop. I captured a T shirt one time with your symptoms.

  25. #25

    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    yep,
    that was one of the first things I looked at.

  26. #26
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    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    single or dual fuel tanks? If dual, remove gas cap to eliminate restricted vent line.
    Capt Bob
    1969 23ft ChrisCraft Lancer
    Merc 5.7L 260HP/ Volvo 280
    1972 22ft Bristol
    Honda 7.5HP 4 stroke Long shaft

  27. #27

    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    OK
    A little update from this weekend.

    I took apart the engine harness and switch it from the other engine....same problem

    I took out the entire fuel system:
    Replaced the carburetor with another Quadrajet.
    Replaced the fuel line all the way to the tank.
    checked the filter and filter housing. ( I had just put them in new last week)
    checked the anti-syphon valve at the tank (was new also from last week)
    checked the tube on the hi pressure side of the fuel pump .
    Reconnected everything and the boat does the same thing. I have changed the fuel pump, three times already.
    The boat runs the same as in the video I posted, the secondary on the carb opens, but I don't see a large volume of fuel going in and he motor still won't rev past 2500 to 2800RPMs, feels like it has no power right from the moment you pull the throttle.
    I can pretty much rule out fuel delivery.
    The only thing I hear different in this engine from the other is a slight knock sound at idle, also there is a rattle in the transmission at low RPMs the goes away after 1200. other than that, it idles very smooth.
    These long blocks were both brand new in the box, the only thing I added were the intake manifolds, which were both purchased new also, and both installed the same day.
    has anyone had a problem with an intake manifold that the engine does not miss or middle rough?
    I am starting to think that the intake manifold could be the problem, the engine has good steady vacuum at idle.
    I would appreciate any suggestions since I am pretty much out of ideas here.

  28. #28
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    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Every time I have had "slight knock sound at idle, also there is a rattle in the transmission at low RPMs that goes away after 1200" I always had a dead cylinder for one reason or the other. Just because it sounds good at higher rpms does not mean it isn't running on seven. If you have not already done so, you might pull the plugs and carefully inspect to see if any are wet or otherwise "different" and then while you have them out do a compression check. Even new engines can drop a valve.



  29. #29
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    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    double and triple check the firing order also.

  30. #30

    Default Re: 454XL, lacks power and won't rev past 2800 RPMs

    Thank you CaboJohn.
    I am not sure about a dead cylinder, but I am starting to think there may be a problem with a connecting rod, main bearing or even a cracked of loose flywheel.
    I did a compression test on the engine and it read 140psi on all cylinders. The spark plugs were very clean, almost brand new, indicating a lean lean engine.
    Here is a link to you tube, I make a short clip of the noise, let me know what you think.
    I am not sure I hear it at high RPMs, only at idle. I will try tonight see if I can record the engine at high RPMs in neutral.
    https://youtu.be/3CWbzcoKUVI

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