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  1. #1

    Question After Engine Rebuild - Lack of power/Acceleration through entire range

    I have a 2011 VP 320HP 5.7GXIC-P engine that blew due to oil pan cracked.
    Outdrive is DPS-A 195 with F5 Duo-Props.
    Boat had good holeshot and 50 plus MPH a 5400 rpms WOT

    After rebuild, engine now has 343HP at 5,000 RPM's and 362 Ft/Lbs torque per dyno.
    I put it in water to test expecting great holeshot and quicker acceleration to top end.

    Boat now is down in holeshot response and acceleration and will only get to 40MPH at 4000 RPM's WOT after some time.
    In neutral, engine will rev over 5000 RPMs no problem

    Someone suggested an F4 prop set may help but that is an expensive maybe.
    Its only 25HP more so ho could that change the characteristic s much.

    Could this be a computer issue, gearing, props, other? PLEASE HELP

  2. #2
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    Quote Originally Posted by JayPW View Post
    I have a 2011 VP 320HP 5.7GXIC-P engine that blew due to oil pan cracked.
    Outdrive is DPS-A 195 with F5 Duo-Props.
    Boat had good holeshot and 50 plus MPH a 5400 rpms WOT

    After rebuild, engine now has 343HP at 5,000 RPM's and 362 Ft/Lbs torque per dyno.
    I put it in water to test expecting great holeshot and quicker acceleration to top end.

    Boat now is down in holeshot response and acceleration and will only get to 40MPH at 4000 RPM's WOT after some time.
    In neutral, engine will rev over 5000 RPMs no problem

    Someone suggested an F4 prop set may help but that is an expensive maybe.
    Its only 25HP more so ho could that change the characteristic s much.

    Could this be a computer issue, gearing, props, other? PLEASE HELP
    I'm not quite sure where to begin.
    I'd have to say that first off, if this 5.7L engine was built to produce 343HP at 5,000 RPM, you most likely had this work performed by an automotive shop.
    Automotive engine builders typically do not understand the Marine version of the SBC, and how to build one correctly.

    In order to produce 343HP at 5,000 RPM, the static compression ratio would be excessive for Marine use.
    This can lead to Detonation.

    Also, if the camshaft profile is incorrect for Marine use, that would also be an issue.

    Since the previous engine was capable of the speeds that you suggest, propping down is not the correct solution.

    My suggestion:
    If this SBC Engine was built per HP Auto specs, you would be better off to pull it and sell it to a Hot Rod enthusiast, and build a more suitable Marine SBC for this boat. Perhaps even a Q/E built 6.3L (aka 383 stroker) for Marine use.

    Also, for what it's worth..... ** excessive horse power/torque may eventually take it's tole on the 1.95:1 lower unit gear set.
    If hell bent on lots of horse power and torque, you may want to go to a 1.78:1 lower gear unit.

    Compared to the 1.78:1 gear set, the 1.95:1 "drive" gear is smaller and the two "driven" gears are slightly larger.
    This means less effective tooth contact causing this gear set to not be as stout as the 1.78:1 gear set.



    ** Can you give us the specs on this hull? If this is a small hull, the 1.95:1 may work OK.

    .
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

    Please... no PMs! Post your questions on the forum.

  3. #3

    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    2011 Chaparral Sunesta 244 - 4800 lbs dry, 8 1/2 feet beam and 24 feet length.
    If I change the lower unit to the 1:78, could that resolve this?
    I am not in position to pull engine and get another one.

  4. #4
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    Quote Originally Posted by JayPW View Post
    2011 Chaparral Sunesta 244 - 4800 lbs dry, 8 1/2 feet beam and 24 feet length.
    If I change the lower unit to the 1:78, could that resolve this?
    I am not in position to pull engine and get another one.
    Perhaps I have been misunderstood.
    Here's what I hear you saying:

    1.... Newly rebuilt 5.7L SBC engine due to previous engine failure.
    2.... New 5.7L SBC engine was built to produce more horse power and torque.
    3.... Real life testing shows that the new engine is NOT performing as well as the previous engine did.

    Something is wrong.... would you agree?

    Either the Static C/R is incorrect causing this engine to undergo Detonation..... or the fuel delivery and/or ignition system is not set up correctly.

    My concern is the alleged claim of 343 HP @ 5k RPM from a GM 5.7L SBC!

    How did the shop achieve this, and yet still build it correctly for true Marine use?

    It may be helpful if you were to post the build specs!
    Piston profile.
    Combustion chamber volume (most likely 65cc)
    S C/R spec.
    Camshaft profile specs.
    etc.



    .
    Last edited by RicardoMarine; 03-07-2018 at 04:21 PM.
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

    Please... no PMs! Post your questions on the forum.

  5. #5

    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    Engine specs
    Hydraulic Roller Camshaft
    Compression Ratio: 9:4:1
    Bore: standard
    Stroke: 3.750"
    Valves: intake 1.94: Exhaust 1.50
    Valve springs: 135lbs 1.255" O. D.
    CRANKSHAFT DIA: 2.650"
    Compress height: 1.560"
    18cc D-cup pistons
    Cylinder compression : 9.6:1

    OMG!

  6. #6

    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range


  7. #7
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    ............................
    Quote Originally Posted by JayPW View Post
    Engine specs
    Hydraulic Roller Camshaft
    This is missing the profile data. I.E., lift, duration, over-lap, etc.

    Compression Ratio: 9:4:1
    That should read 9 point 4 to 1

    Bore: standard
    Re-manufactured engines are rarely of a standard bore.

    Stroke: 3.750"
    The 3.750" stroke is from the 400 cu in SBC.... the 5.7L SBC stroke is 3.480".

    Valves: intake 1.94: Exhaust 1.50
    Valve springs: 135lbs 1.255" O. D.
    CRANKSHAFT DIA: 2.650"
    Compress height: 1.560"

    18cc D-cup pistons
    Cylinder compression : 9.6:1
    When I run the calcs for a Std 4.000" bore 5.7L with 65cc chambers, 18cc piston dish volume and a of .039" Q dimension, I get 8.86:1
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

    Please... no PMs! Post your questions on the forum.

  8. #8
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    If you using the old damper pully on the crank check for true tdc with a piston stop tool. Once to verify true tdc then check the progressive spark advance is to spec for a marine application. Detonation will trash that new engine faster than anything else. Our marine engines work hard full time it is like pulling a trailer full of bricks up a mountain pass take your foot off the pedal you stop.
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  9. #9

    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    Its not a remanufactured engine, it was just used to spec out he parts . Cylinders were only honed. I will get clarification.

  10. #10
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    Quote Originally Posted by JayPW View Post
    Its not a remanufactured engine, it was just used to spec out he parts . Cylinders were only honed. I will get clarification.
    Although I know better to jump in on this thread....Here it goes.

    Listen to what Ricardo is saying... WHERE ARE THE CAM SPECS? The incorrect cam will not let your engine rev in a marine environment.

    When they ran your engine on the dyno did they use your ignition system, Carburetor and balancer? If yes, my money would be on an incorrect build for marine use.

    The only Auto cam shaft that is CLOSE to a marine cam is a "Truck Use" cam shaft.....

    "When I run the calcs for a Std 4.000" bore 5.7L with 65cc chambers, 18cc piston dish volume and a of .039" Q dimension, I get 8.86:1 "

    Rick, did you add in for the reduced block deck and the decking of the heads and you know this block was bored at least 30 over.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  11. #11
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    ...............
    Quote Originally Posted by JayPW View Post

    After rebuild, engine now has 343HP at 5,000 RPM's and 362 Ft/Lbs torque per dyno.
    I put it in water to test expecting great holeshot and quicker acceleration to top end.

    I gathered from the above that your existing SBC engine was rebuilt.... yes/no?
    Quote Originally Posted by kimcrwbr1 View Post
    If you using the old damper pully on the crank check for true tdc with a piston stop tool. Once to verify true tdc then check the progressive spark advance is to spec for a marine application. Detonation will trash that new engine faster than anything else.
    Kim is spot on!
    Short of no oil pressure and/or over-heating.... "Detonation" is the Marine Gasser's worst enemy!

    The harmonic balancer TDC notch must be dead on with regard to the tab notch!
    It is imperative that it represent true crankshaft angle @ #1 TDC.
    If in doubt, I would suggest that you perform a PPS (positive piston stop) procedure.
    Quote Originally Posted by Docksidemarineservices View Post
    Although I know better to jump in on this thread....Here it goes.
    Please do...... you are very knowledgeable.

    Listen to what Ricardo is saying... WHERE ARE THE CAM SPECS? The incorrect cam will not let your engine rev in a marine environment.
    Agreed!

    When they ran your engine on the dyno did they use your ignition system, Carburetor and balancer? If yes, my money would be on an incorrect build for marine use.
    Well, my thoughts are..... if this 5.7L SBC is truly producing 343 horse power @ 5k RPM, it is most likely not a true Marine build. It is more likely to be an Automotive build!

    The only Auto cam shaft that is CLOSE to a marine cam is a "Truck Use" cam shaft.....
    Quote Originally Posted by Rick
    "When I run the calcs for a Std 4.000" bore 5.7L with 65cc chambers, 18cc piston dish volume and a .039" Q dimension, I get 8.86:1
    Rick, did you add in for the reduced block deck and the decking of the heads and you know this block was bored at least 30 over.
    If the Q dimension is correct (as it should be), the deck height should not make much difference.
    If the cylinder heads were shaved by .010", this too would not make a huge difference as long as good Q dimension was established.

    Even if I reduce the 65cc to 64cc (and run the calcs again), it only changes the C/R to approx 9.0:1.

    In other words..... I'm thinking that by taking .010" off each head, it would not reduce the chamber volume by 1cc. So, my change from 65cc to 64cc is exaggerating the C/R calcs!

    As for the bore...... the OP says that the bore is standard.... of which would be 4.000"!

    OK.... to further this, a true 5.7L SBC Marine Engine must be built correctly.
    It is imperative that:
    ...... a quench effect be incorporated. This means NO GM full dished pistons, and a Q/E dimension of approx .038"!
    ...... a suitable S C/R must be incorporated.
    ...... the camshaft profile must be correct.
    ...... the ignition advance throughout the RPM range must be correct. This means that the TDC markings must be accurate, and it also means that the balancer should be marked off up to approx 35 degrees BTDC, and that the advance be verified throughout the RPM range as per Marine specs.

    When it comes down to it........ LPCP is of ultimate importance.
    LPCP = location of peak cylinder pressure.
    LPCP should occur at/near 12* to 14* ATDC. That means After Top Dead Center.

    When all else is correct (meaning that the correct components were used in the build), the ignition advance is given the last word with regard to the placement of LPCP.


    This freshly rebuilt 5.7L SBC engine should at least perform as well as the previous engine did.
    Last edited by RicardoMarine; 03-08-2018 at 09:29 AM.

  12. #12
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    Quote Originally Posted by JayPW View Post
    Its not a remanufactured engine, it was just used to spec out he parts . Cylinders were only honed. I will get clarification.
    Please explain!


    .
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

    Please... no PMs! Post your questions on the forum.

  13. #13
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    Hi all I am the builder of Jay's engine and I have been extremely frustrated with the outcome.
    First one to ever do this, I have built dozens of them with great success.
    Engine specs are as jay posted and engine did not need boring as his engine had been very well maintained and not abused therefore cylinders were not scared or worn beyond specs for use of stock oem kits. Engine therefore was only honed and polished.
    His original fuel system and ignition was used with exception of replacing the distributor.
    It is a vortec 5.7gxi 3rd generation.
    The distributor is a flat top and contains the cam position sensor. Also there is new crank position sensor and Harmonic balancer.
    The problem is that the engine performs well until under a load.
    Under load it immediately goes (wot) no Hesitation, backfiring, missing or lag.
    And maintains good throttle without any indication that it is out of time or lacking power.
    It takes longer to get up on plane once on plane tops out at 40mph @ 4000 rpm.
    The power band arc is at 4800.
    It will stand the boat up on launch but while trimming it losses that thrust.

  14. #14

    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    Yes...Existing engine rebuilt!

  15. #15
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    Quote Originally Posted by MandMcustomperformance View Post
    Hi all I am the builder of Jay's engine and I have been extremely frustrated with the outcome.
    First one to ever do this, I have built dozens of them with great success.
    Engine specs are as jay posted and engine did not need boring as his engine had been very well maintained and not abused therefore cylinders were not scared or worn beyond specs for use of stock oem kits. Engine therefore was only honed and polished.
    His original fuel system and ignition was used with exception of replacing the distributor.
    It is a vortec 5.7gxi 3rd generation.
    The distributor is a flat top and contains the cam position sensor. Also there is new crank position sensor and Harmonic balancer.
    The problem is that the engine performs well until under a load.
    Under load it immediately goes (wot) no Hesitation, backfiring, missing or lag.
    And maintains good throttle without any indication that it is out of time or lacking power.
    It takes longer to get up on plane once on plane tops out at 40mph @ 4000 rpm.
    The power band arc is at 4800.
    It will stand the boat up on launch but while trimming it losses that thrust.

    I'm glad that you posted to his thread.

    Would you be willing to post the exact build specs for us?

    Piston profile. (GM full dished.... or a Q/E style profile?)
    Quench dimension.
    Deck height.
    S C/R.
    Camshaft profile.
    Was the camshaft indexed differently?
    Cylinder head chamber volume.
    Which ignition system?
    Ignition advance curve throughout the RPM range.

    Also, Jay mentioned early that the stroke was 3.750", yet he suggests that this is a 5.7L SBC. I assume that this was in error!


    .

    Last edited by RicardoMarine; 03-08-2018 at 10:29 AM.
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

    Please... no PMs! Post your questions on the forum.

  16. #16
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    Did you check for true tdc with a piston stop?
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  17. #17
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    Yes I will pull up the exact build specs and post may be later on today as I am very busy but will post.

  18. #18
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    As stated
    It is electronic ignition meaning it won't start of not on TDC and if it were possible would not idle correctly or even stall and die.
    Ecm controls timing at idle and advance throughout rpm range.

  19. #19
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    Will be back on later on

  20. #20
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    It is real common for the damper rubber bushing to slip giving you a false tdc use a piston stop tool to check the damper and confirm true tdc before you can set base timing.
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  21. #21
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    Quote Originally Posted by MandMcustomperformance View Post
    As stated
    It is electronic ignition meaning it won't start of not on TDC and if it were possible would not idle correctly or even stall and die.
    Ecm controls timing at idle and advance throughout rpm range.
    Just an FYI and FWIW....... with the harmonic balancer correctly indexed and correctly marked off, we can strobe the timing marks (using a Non-Digitally advancing light) and see just where the spark lead is at the various RPM, including at the TA Full In RPM.
    I have never let an engine go out the door without having verified this!

    Too little, and we leave power on the table!
    Too great, and we risk detonation damage!
    It's all about the proper LPCP
    !
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

    Please... no PMs! Post your questions on the forum.

  22. #22
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    Okay guys I have a few minutes here are the recorded measurements for Jay's engine.


    Camshaft Style:Hydraulic flat tappet
    RPM Range:1,000-5,000
    Intake Duration at 050 inch Lift:212
    Exhaust Duration at 050 inch Lift:218
    Duration at 050 inch Lift:212 int./218 exh.
    Valve Lift with Factory Rocker Arm Ratio:0.447 int./0.462 exh.
    Lobe Separation (degrees):112


    Crankshaft
    Journal Diameter
    No. 1 2.4484
    No. 2, 3, 4 2.4481
    No. 5 2.4479
    Taper .0002
    Out of Round .0002

    Main Bearing Clearance
    No. 1 .0007
    No. 2, 3, 4 .0022
    No. 5 .00250
    Crankshaft End Play .002
    Connecting Rod Journals
    Diameter 2.0978
    Taper .0003
    Out of Round.0003
    Rod Bearing Clearance .0006
    Rod Side Clearance .006

    Deck height 6.358

    Bore 4.00

    Stroke 3.480

    Dish pistons
    Clearance. 0020
    Volume +7.00cc

    Ring clearance
    Top .014
    2nd.014
    Oil .011

    Valves 1.94 int/1.50exh.

    Cylendar volume 64cc

    Average compression 9.4:1

    RPM curve is 346hp / 360ft,lbs @ 4800

    Ingnition is GM (OEM) coil distributor and module.

    fuel pressure is 23.5 @ 3000 rpm.

    Fuel system is stock dual pump w/separator

  23. #23
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    Rick yes TDC was accomplished correctly and as stated timing cannot be adjusted with that distributor everything is set to [email protected] and ecu takes over.

  24. #24
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    That was supposed to read Cylendar head volume 64cc

  25. #25
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    Did you by chance advance the cam timing.?
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  26. #26
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    So as you can see this was a refresh build and rotating kit is OEM direct replacement

  27. #27
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    I tried that with Degree Wheel @ 10 degrees btdc
    and it would not start. Put it back on TDC it fired right up.

  28. #28
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    I've been accused of being too precise and picky at times that's why I write down all measurements

  29. #29
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    So, the timing gear set was installed without any advance?
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  30. #30
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    Default Re: After Engine Rebuild - Lack of power/Acceleration through entire range

    With advance it would not start

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