454MAG 24' Baja 23P Mirage Prop & Only turning 4000RPM WOT????
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454MAG 24' Baja 23P Mirage Prop & Only turning 4000RPM WOT????

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    Junior Member bertus951's Avatar
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    Default 454MAG 24' Baja 23P Mirage Prop & Only turning 4000RPM WOT????

    Hello Everyone,

    I am new to the I/O scene and am not too sure if this is right. I just bought a 24' Baja with a 454mag in it and I am only turning 4000rpms. Motor is all stock, no mods. I have had a few people say that it could be my prop, which is a Quicksilver Mirage counter 23P prop. For some reason I don't think it would be my prop causing me to only run @ 4000RPM's WOT. I had a 454 in an older jet that would run @ 5500-6000 rpms all day and that was a stock build motor as well. Any ideas on what it could be? Could it be my prop? I have checked for vacuum leaks and there aren't any. There is a vacuum port coming off of my dizzy that does not have a vacuum line hooked up to it, may that be it? If it is, where would the vacuum line go to? The carb? Any advise on where to start or any ideas would be greatly appreciated!!

    Thank you!!!
    Bertus

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    Senior Member GT Jets's Avatar
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    Quote Originally Posted by bertus951 View Post
    Hello Everyone,

    I am new to the I/O scene and am not too sure if this is right. I just bought a 24' Baja with a 454mag in it and I am only turning 4000rpms. Motor is all stock, no mods. I have had a few people say that it could be my prop, which is a Quicksilver Mirage counter 23P prop. For some reason I don't think it would be my prop causing me to only run @ 4000RPM's WOT. I had a 454 in an older jet that would run @ 5500-6000 rpms all day and that was a stock build motor as well. Any ideas on what it could be? Could it be my prop? I have checked for vacuum leaks and there aren't any. There is a vacuum port coming off of my dizzy that does not have a vacuum line hooked up to it, may that be it? If it is, where would the vacuum line go to? The carb? Any advise on where to start or any ideas would be greatly appreciated!!

    Thank you!!!
    Bertus

    Bertus,

    Please take no offense, but your in a bit over your head...

    First...Leave the vacuum port alone. No help to be had there....

    Second, your prop may be a little tall, but still think 4000 RPM is short.

    Third, verify your tachometer with a known good one..

    Fourth, check, or have someone check the ignition timing at over 2500 RPM (this can be done on the flusher) you should be in the mid 30's in degrees before top dead center.

    And last of all, fifth, do not ever and I mean ever compare an I/O to a jet again...... Completely different animal...

    I will let it slide because you're the new guy....Gotta play nice you know...
    GT


    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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    Senior Member kiethco's Avatar
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    Hi Bertus,
    I too find your rpm interesting. I have a 454 Bravo, 330 h.p., that is overrevving a 21p stainless prop, I hit 5100 with more on the throttle. I want to try a 23, I believe it should drop my rpm by 400 or so. If you'd like to try a 19 or 21 I have both you can use if you like. They're new aluminum. I'd like to try your 23.
    I'm in Long Beach if you want to come down and run in salt water, otherwise I can meet you at Elsinore or something.

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    New here Beer:30's Avatar
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    Quote Originally Posted by GT Jets View Post
    And last of all, fifth, do not ever and I mean ever compare an I/O to a jet again...... Completely different animal...

    I will let it slide because you're the new guy....Gotta play nice you know...
    True, completely different animal. In fact, you SHOULD have your vac advance hooked to timed (throttle) vac port on front of carb. With an outdrive, you WILL have SOME vacuum during cruise - unlike a jet.

    Is vacuum advance your problem?? NO. It only comes into play during part-throttle cruise, and disappears at WOT.

    ALSO, check your throttle cable. Push the stick all the way forward and make sure you are getting WOT. Naturally, do this with the engine OFF. After the throttle is pushed completely forward, disconnect it at the carb/throttle body and see if you can open the throttle MORE than it already was.
    Quote Originally Posted by gn7 View Post
    EFI is the wave of the future. There can be no denying it. Electronics have been on the leading edge of our entire lives. Not only os the magneto dead, but the standard issue CDI is wavering. Its all about total fuel, air AND spark control. Anybody that thinks its not has their head up their ass.


    2001 SleekCraft 30' Heritage SSB, open-bow mid-cuddy. 496HO / Bravo-I.

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    Bass Lake Dream'n "Flat" foot'n's Avatar
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    If its a 454mag then it's an mpi. I would check that the butterflies are opening all the way at WOT (engine off please) and also, are you trimming the drive up while at speed?
    [email protected]


    BLOWN GAS FLAT TO THE RAMP

    REST IN PEACE MY FRIEND

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    Senior Member h2oracer's Avatar
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    Are you sure it's a magnum ? My 26' Warlock with a 330hp 454 would only spin 4200 rpm with a 23p quicksilver mirage. 4,000 rpm is too low you may be over proped for your hull even if it is a magnum. If it is a magnum find out what the max rpm is. Maybe other Baja owners on this sight can relay their experiance.

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    Quote Originally Posted by bertus951 View Post
    Hello Everyone,
    h
    I am new to the I/O scene and am not too sure if this is right. I just bought a 24' Baja with a 454mag in it and I am only turning 4000rpms. Motor is all stock, no mods. I have had a few people say that it could be my prop, which is a Quicksilver Mirage counter 23P prop. For some reason I don't think it would be my prop causing me to only run @ 4000RPM's WOT. I had a 454 in an older jet that would run @ 5500-6000 rpms all day and that was a stock build motor as well. Any ideas on what it could be? Could it be my prop? I have checked for vacuum leaks and there aren't any. There is a vacuum port coming off of my dizzy that does not have a vacuum line hooked up to it, may that be it? If it is, where would the vacuum line go to? The carb? Any advise on where to start or any ideas would be greatly appreciated!!

    Thank you!!!
    Berths
    merc specs 7.4mpi 4200-4600 454 mag mpi 4600-5000 do you have a VST tank on yours my 95 502 did 415hp had one an it gave me hell stalling low rpm vapor locking that was due to bad O rings on the tank also check water temp sensor I could be read low temp could have you in choke mode an be runing rich If you have EFI also your map sensor can be bad causing wot problems it wouldn't hurt to check fuel rail pressure an check each injector make sure all 8 are consitain with spray an an the factory merc MPI don't flow much more after 5200-5500 the cfm drops off I have seen it first hand on the dyno

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    Junior Member bertus951's Avatar
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    Thanks everyone for the input. I am starting to thing that maybe I dont have a 454 Mag, or at least the motor isn't fuel injected, it is carburated, so maybe not an MPI. The cover that goes over the carb says 454 Magnum / Bravo 1. By VST tank, do you mean a fuel tank that is in the belly of the boat? If yes, then yes, that is what I have. Would vapor lock occur if there wasnt a relief vent? My fuel tank has a relief vent that exits right new to the fill hole. @ H2O racer, if you were running a 23P with the same motor/drive set up but in a 26' boat and turning higher RPM's, shouldnt my boat be turning a little bit higher than yours did since its not as long/heavy of a boat? Just thinking out loud here. @ Flat Foot, yes I am setting the trimming up slightly at 4k rpm's and setting the trim tabs as well. I toyed around with them a little to find the boats sweet spot. I will definitely check the throttle cable, I dont know why i didnt think of that . @ GT, I always expect a little hazing from someone....lol. I dont take things seriously and you had provided me with a lot of help a long time ago on SCJB when I had my jets.

    I am going to check the throttle cable, RPM's at 2500 to see degree off TDC, and verify my Tach's RPM's with another one I have.

    Thank you everyone for you feedback!!!!

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    Senior Member h2oracer's Avatar
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    [QUOTE=bertus951 H2O racer, if you were running a 23P with the same motor/drive set up but in a 26' boat and turning higher RPM's, shouldnt my boat be turning a little bit higher than yours did since its not as long/heavy of a boat? Just thinking out loud here.

    A fair comparison would be with a Baja equiped like yours with the same weight load. One would think that your boat would turn higher rpm's than mine but that isn't always the case. I would find a 21p mirage to try. It will bring the r's up.

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    [QUOTE=h2oracer;1637541][QUOTE=bertus951 H2O racer, if you were running a 23P with the same motor/drive set up but in a 26' boat and turning higher RPM's, shouldnt my boat be turning a little bit higher than yours did since its not as long/heavy of a boat? Just thinking out loud here.

    A fair comparison would be with a Baja equiped like yours with the same weight load. One would think that your boat would turn higher rpm's than mine but that isn't always the case. I would find a 21p mirage to try. It will bring the r's up.[/QUOTE]
    no a VST tank is only on the early mid 90s fuel injection motors its a vapor seprating tank it was replaced with the cool fuel system they use now 10X better so if you have a carb then check timing cap rotor an look for corrosion in the distributor make sure the choke is not stuck on fuel filters an be sure your air cleaner is not restricted after all that good stuff an its running good start prolong down an try an see it rpm comes up but I'm afraid that a stock 454 merc carb will only do 4600 max rpm

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    Senior Member h2oracer's Avatar
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    [QUOTE=neil450;1637567]
    Quote Originally Posted by h2oracer View Post
    no a VST tank is only on the early mid 90s fuel injection motors its a vapor seprating tank it was replaced with the cool fuel system they use now 10X better so if you have a carb then check timing cap rotor an look for corrosion in the distributor make sure the choke is not stuck on fuel filters an be sure your air cleaner is not restricted after all that good stuff an its running good start prolong down an try an see it rpm comes up but I'm afraid that a stock 454 merc carb will only do 4600 max rpm
    4600 is the recomended max rpm for the carbed 330hp 454. They will spin higher. I've done it but it's not a good idea. Rpm depends on how the boat is proped.

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    [QUOTE=h2oracer;1637590]
    Quote Originally Posted by neil450 View Post

    4600 is the recomended max rpm for the carbed 330hp 454. They will spin higher. I've done it but it's not a good idea. Rpm depends on how the boat is proped.
    my 06 merc 525 hits the limter at 5400 whipple has a tuned ecm for an it gains 400 or so more but if you want a long life out of your boat don't over rev it your valve springs will start to go first then its all down hill from their

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    Senior Member h2oracer's Avatar
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    [QUOTE=neil450;1637616]
    Quote Originally Posted by h2oracer View Post
    my 06 merc 525 hits the limter at 5400 whipple has a tuned ecm for an it gains 400 or so more but if you want a long life out of your boat don't over rev it your valve springs will start to go first then its all down hill from their
    The 454 that I did this in was in a 22ft eliminator not my warlock. I only did it one time to see how fast the boat would go and backed off. I would be more worried about the rods than the valve springs.

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    New here Beer:30's Avatar
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    Quote Originally Posted by bertus951 View Post
    @ H2O racer, if you were running a 23P with the same motor/drive set up but in a 26' boat and turning higher RPM's, shouldnt my boat be turning a little bit higher than yours did since its not as long/heavy of a boat? Just thinking out loud here. @ Flat Foot, yes I am setting the trimming up slightly at 4k rpm's and setting the trim tabs as well.

    I am going to check the throttle cable, RPM's at 2500 to see degree off TDC, and verify my Tach's RPM's with another one I have.

    Thank you everyone for you feedback!!!!
    If you are trimming up, then you shouldn't be on the trim tabs at all. You use the trim tabs for dumping the nose down some more, if neutral (zero) trim doesn't give you enough cut for rough water. Tabs cause drag (variable, depending on how much of them you have touching water), and thus - eat power and RPM. If you are trimmed up until you start to lose speed / then back down a bit, you would ONLY use the tabs to settle down some chine walk. You had BETTER NOT be having chine walk at 4000rpm with 330 hp. Mine won't even chine walk up on the steps at 65 trimmed to the hilt!

    Leave the tabs alone until you get your top speed worked out.
    Last edited by Beer:30; 05-21-2012 at 05:37 PM.
    Quote Originally Posted by gn7 View Post
    EFI is the wave of the future. There can be no denying it. Electronics have been on the leading edge of our entire lives. Not only os the magneto dead, but the standard issue CDI is wavering. Its all about total fuel, air AND spark control. Anybody that thinks its not has their head up their ass.


    2001 SleekCraft 30' Heritage SSB, open-bow mid-cuddy. 496HO / Bravo-I.

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