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  • Guest's Avatar
    Guest replied
    HI i have read a lot on this forum about pistons as i said i have lt1 pistons and have had them for two seasons now. i use the boat the throtle is like a switch to get to whear we ski .flat out and again on way back with a lot of skiing and wakebording in between. i had the heads off the end of this year the pistons and bores valves all as i put them in .

    Leave a comment:


  • 2850Bounty
    replied
    Just Relax wrote:
    ....... I wanna do the following.. captains call exhaust, comp cam, edelbrock intake and carb package, msd ignition package which includes distributor, and maybe have heads port and polished.

    So my question is
    • 1 wrote:
    • can the stock bottom end withstand these upgrades?
    • Does this engine have a four bolt main?



    bkaltec.........
    bkaltec wrote:
    1.... My posts are intended to answer the questions asked.

    2..... If the user is not intelligent enough to ask the correct questions, or knowledgeable enough to understand the mechanics of an engine, then that's their problem.

    3.... GM used 2 bolt mains in light trucks (silverado/sierra 1500's)

    4.... Load is simply load, and load is not specific to its application. Reguardless if its a boat, tow vehicle or what ever. You need to build an engine to your application and load you plan to run it.

    5..... The small block engine was engineered for automotive use, and modified for marine use, dont over exaggerate the differences.
    1.... See above.... those are his two initial questions.

    2... People come to an on-line forum to ask these questions in hopes of receiving good sound information, and information that does not deviate from the "Norm" without clarification.

    IOW, if you were to recommend the F/T pistons being used with the 64cc chamber Vortec cylinder heads (w/ 5.7L stroke), at least explain what this higher C/R may mean in terms of his potential usage.

    The OP may not own a small boat as you do.

    3.... Why not inform the OP that his casting number may lead him to this info.

    4.... Again..... Small boat -vs- Cruiser analogy.... Apples/Oranges!

    5.... Here's where you and I part ways (both #4 and #5)... so there's no sense in dicussing it further!

    *****************

    bkaltec, in no way am I suggesting that YOU are not knowledgeable....... you certainly appear to be! You've taken automotive components and have made modifications to them for a Marine adaptation, and have pulled it off.... :cool

    AND you haven't blown yourself up yet! :kidding

    I'm simply asking that you at least qualify this so that the reader understands that YOUR scenario is a bit unique.

    And perhaps let them know that you are applying your skills and build techniques to a 19 foot boat... not a cruiser size boat .... of which would take us back to #5.

    Fair nuff?

    .

    Leave a comment:


  • Guest's Avatar
    Guest replied
    My posts are intended to answer the questions asked. If the user is not intelligent enought to ask the correct questions, or knowledgeable enough to understand the mechanics of an engine, then thats their problem.

    yachtman wrote:
    I could be wrong but most of the truck blocks that GM uses are 4 bolt mains.
    GM used 2 bolt mains in light trucks (silverado/sierra 1500's)

    2850Bounty wrote:[LIST]1 wrote:[*]4.030" bore, 3.480" stroke, F/T's with 64 cc chambers?

    Using a compressed H/G thickness of .021", a piston deck height of .016"........ that equals a C/R of 11.140407874512256 : 1 !

    You've been able to pull this off due to it being installed a small Capri 1950.

    For you guys with larger cruisers, DO NOT do this....., you'd be better off to build the C/R down from this!
    Load is simply load, and load is not specific to its application. Reguardless if its a boat, tow vehicle or what ever. You need to build an engine to your application and load you plan to run it.

    The small block engine was engineered for automotive use, and modified for marine use, dont over exaggerate the differences.

    Clearly my first reply was not read entirly, so ill reitterate.

    bkaltec wrote:
    I run premium in my boat without issues.
    This means 91 octane +

    bkaltec wrote:
    Keep in mind I run exclusivly in fresh water.
    This means no salt, and the boat is out of the water 90% of the time.

    Leave a comment:


  • Guest's Avatar
    Guest replied
    Thanks to everyone thus far for their input. I think the moral of the story is that there are endless ways I could go with this, and one could make almost anything work. I really am impressed with the build quality of this boat, and like I said it is excellent shape. I'll start with just doing the exhaut diverters and some EMI thunder headers for now, and see how it operates. The PO claims the boat did over 55mph GPS, so really that is plenty fast for a 21 foot bowrider. After all, I'm not going to race this thing, I just want it to run as strong as possible, I HATE underpowered boats, which is what I seem to have always owned, so if this thing jumps up on plane quick and is reliable with the minor mods I'll be more than happy!!

    Leave a comment:


  • yachtman
    replied
    bkaltec wrote:
    A preface:

    I run a modified 355 SBC

    1994 Truck engine.

    Stock rotating assy, 2 bolt mains.

    Speed Pro flat top pistons.

    Vortec heads

    GMPP aluminum vortec TBI intake

    Comp Cams XE 272 hyd/roller

    Roller rockers

    454 TBI with 71#/hr injectors @ 30psi

    Stock GM HEI dist.

    EMI Thunder Aluminum exhaust

    Stock OMC Cobra drive.

    To answer your first post...

    If you are going to take apart the top end heres a few ideas.

    Since you are thinking about purchasing an intake manifold, consider new heads. You can find some very inexpensive SBC Vortec heads. As long as the pistons are NOT domed you are fine, it will bump the compression up a little, but so will the HP. I run premium in my boat without issues. Mind the lift as previously mentioned.

    As for aluminum components, dont fret. Ive had my aluminum intake for 3 seasons, had it apart last winter when I enlarged the throttle body bores, and there was NO evidence of corrosion. Same with my aluminum exhaust manifolds. Keep in mind I run exclusivly in fresh water.
    Hhhhmmmm..... you engine specs give me pause.

    I could be wrong but most of the truck blocks that GM uses are 4 bolt mains.

    Vortec heads aren't generally usable with flat top pistons as the vortec heads have 64cc chambers and the compression would be too high for marine applications unless you want to use octane booster all day.

    Aluminum heads and intakes are not acceptable in a marine applications unless its a closed cooling system. Yeah it will work for a time. Not all waters are the same.

    A stock automotive distributor is anosultely not acceptable is not coastguard approved is illegal and can be extremely dangerous.

    But to each his own who am I to tell you what to put in your boat?

    Leave a comment:


  • 2850Bounty
    replied
    bkaltec wrote:
    A preface:
    • 1 wrote:


    • Speed Pro flat top pistons.

      Vortec heads
    • Since you are thinking about purchasing an intake manifold, consider new heads. You can find some very inexpensive [SIZE]4 wrote:
      SBC Vortec heads.[/SIZE] As long as the pistons are NOT domed you are fine, it will bump the compression up a little, but so will the HP.
      ..........
    • As for aluminum components, dont fret. Ive had my aluminum intake for 3 seasons, had it apart last winter when I enlarged the throttle body bores, and there was NO evidence of corrosion. Same with my aluminum exhaust manifolds. Keep in mind I run exclusivly in fresh water.



    • 1 wrote:
    • 4.030" bore, 3.480" stroke, F/T's with 64 cc chambers?

      Using a compressed H/G thickness of .021", a piston deck height of .016"........ that equals a C/R of 11.140407874512256 : 1 !

      You've been able to pull this off due to it being installed a small Capri 1950.

      For you guys with larger cruisers, DO NOT do this....., you'd be better off to build the C/R down from this!
    • [COLOR]"#FF0000" wrote:
      Please.... be very careful when you make a suggestion like this to those who may not understand the SBC Marine Engine components. [/COLOR]

      Existing short block: select a cylinder head and combustion chamber volume that is suitable for the existing piston configuration.

      Existing empty block with cylinder heads: Select a piston that compliments the cylinder head combustion chamber volume.

      The other components can be tailored and varied!

      I quote you from another thread:
      If youre knowledgable and have some common sense, its not difficult to understand what parts should be "Marine Grade" and/or retain the same qualities.
      Nothing personal here, but please consider that others read these threads, and that they may take this as good over-all information without fully understanding it or without researching it further.
    • I'm glad that it is working you......, but the fresh lake/river water (and perhaps a good flushing) is why you have been able to pull this off for this rather short duration.

      I'll keep my fingers crossed for you, and hope that it continues working!




    MR HAWKINS wrote:
    ......... i run a 350 in my regal 190 br (sory just got a bayliner) it has 2 bolt mains pistons from a lt1 all of which woz ballanced.......
    Interesting to hear you say that LT 1 pistons were used. Typically we steer clear of short skirt pistons for Marine Cruiser use!

    Leave a comment:


  • Guest's Avatar
    Guest replied
    hi i run a 350 in my regal 190 br (sory just got a bayliner) it has 2 bolt mains pistons from a lt1 all of which woz ballanced. a 350 mag cam standard heads with a 3 way valve job roller rockers 1.5.1 350 mag inlet 2inch carb spacer a 670cfm holly standard thunder bolt .and an alpha one gen two with drive shower and regular oil changes.so far it has lasted two seasons hard use.the boat is heavy with full tank and 4 on bord can hit 50 mph at that speed it emptys the fule tank at an alarming rate. skiing and wakebording fantastic fule econamy beter than the 4.3 it replaced.

    Leave a comment:


  • Guest's Avatar
    Guest replied
    A preface:

    I run a modified 355 SBC

    1994 Truck engine.

    Stock rotating assy, 2 bolt mains.

    Speed Pro flat top pistons.

    Vortec heads

    GMPP aluminum vortec TBI intake

    Comp Cams XE 272 hyd/roller

    Roller rockers

    454 TBI with 71#/hr injectors @ 30psi

    Stock GM HEI dist.

    EMI Thunder Aluminum exhaust

    Stock OMC Cobra drive.

    To answer your first post...

    If you are going to take apart the top end heres a few ideas.

    Since you are thinking about purchasing an intake manifold, consider new heads. You can find some very inexpensive SBC Vortec heads. As long as the pistons are NOT domed you are fine, it will bump the compression up a little, but so will the HP. I run premium in my boat without issues. Mind the lift as previously mentioned.

    As for aluminum components, dont fret. Ive had my aluminum intake for 3 seasons, had it apart last winter when I enlarged the throttle body bores, and there was NO evidence of corrosion. Same with my aluminum exhaust manifolds. Keep in mind I run exclusivly in fresh water.

    Leave a comment:


  • 2850Bounty
    replied
    Abigayle III wrote:
    I have found that throwing money into a motor to make your boat go faster is a huge waste of time and money, your original hull isn't designed to go that fast usually...............

    I just like to cruise along slowly and enjoy the scenery.....
    I'm not sure that it's a waist of time/money!

    No two people are going to view this in the same way.... and no two people will have the same budget.

    If the boat is under powered right from the factory, as many were/are, it may very well be worth it to some.

    Don't you think that we tend to over-load our hulls from the conditions in which the factory tests and then further designs from? I do!

    We all know that the ole trick when selling a boat, is to do the sea trial while lightly loaded.

    As Doug pointed out, get these things up on plane, and then a bit more...... and that becomes your best planing speed.

    Perhaps not the best fuel economy.... but the best planing speed AND fuel economy while planing.

    I'm not suggesting that more speed is the goal.... I'm suggesting that getting her up and out of the water, may work better!

    If she struggles to do that, then isn't a bit more power helpful?

    Leave a comment:


  • Guest's Avatar
    Guest replied
    itsabowtime2 wrote:
    Something to consider in all this is the Alpha drive is rated for a max of 300hp. I believe stock your engine is 250hp.
    Although not their brightest move, Sea Ray used the Alpha Gen 1 in the mid 80's Pachanga with a 454 until the Bravo 1 came out in 1988. It may handle a bit more..... :surr it was on my short list of cuddies)

    Leave a comment:


  • Guest's Avatar
    Guest replied
    I have found that throwing money into a motor to make your boat go faster is a huge waste of time and money, your original hull isn't designed to go that fast usually. If your boat does 40 and you want to go 60, go buy a boat that does 60 with a stock motor.... With a boat it takes about $1000. dollars or more to gain 1 mph and your going to spend alot of time on motor issues. They make boats that will do 130 from the factory if you want to go that fast some place.

    I just like to cruise along slowly and enjoy the scenery.....

    Leave a comment:


  • Guest's Avatar
    Guest replied
    Just Relax wrote:
    comp cam, edelbrock intake and carb package, msd ignition package which includes distributor, and maybe have heads port and polished.
    I don't think you'll have to worry about the drive handling the power. The upgrades listed are more for reliability than power increase over stock.

    You might get 5HP from the open exhaust, and maybe 5HP from tidying up the heads.

    Changing to a certain brand of cam- I don't see the point in that. Most aftermarket marine grind cams are just copies of the original Mercruiser spec.

    The Edelbrock intake and carb is usually just chosen as a more serviceable unit and for it's newness and simplicity over the Qjet..

    Ignition is a reliability upgrade, not typically adding HP above stock.

    Leave a comment:


  • Guest's Avatar
    Guest replied
    captharv wrote:
    In 1988, 5.7s rated at 260 HP had quadrajets. They may not be the best marine carb going, however, a simple carb change will not increase the HP THAT much. Theres also a performance/cost ratio.

    As far as the open exhausts are concerned, hear this:

    The engine is tuned for the underwater exhaust. While its possible to add the loud and obnoxious open exhausts, you would have to re-jet the carb, and really play with the distributor advance.

    A thought here.......

    The 1988 mercs had the thunderbolt IV system. The newer merc use teh t-bolt V. The diffreence is a knock monitoring system which increases the timing until the motor kn ocks and then backs it off ubtil it just stops. This is the optimal timing for any situation. The 5.7 with tbolt IV and a 2 BBL is rated at 230 HP. The 5.7 with a t bolt V and a 2bl is rated 250. If, by converting to the t-bolt V you can get a 20-25 HP increase, and BTW, also reduces fuel burn, it may be worth the cost.

    What you would need:

    The t-bolt V modules.

    A knock sensor and the mount ( right side engine drain thingie is where its mounted)

    some wiring fron teh sensor to the module.

    It should be a screwdriver and wrench installation.

    The coil and distributor sensor are the same ( and don't screw with them)
    You mention upgrading to the Thunderbolt 5 ignition system, what about upgrading to something like the MSD system, which comes with their distributor/ coil and ignition control module? below is the link...

    [U]http://www.keitheickert.com/p-13520-...tall-deck.aspx

    Leave a comment:


  • 2850Bounty
    replied
    Harv, I'm not suggesting that the Thunderbolt Ignition subtle changes do not make for more HP..... they may indeed.

    I would want to look at the numbers before getting all excited.

    I think that we should pay close attention to the RPM ranges where Merc rated the HP.

    Take the new and exciting 5.7L Vortec of some years ago.

    We'll see 315 to 320 horse power on some of these engines, and this is with the Full Dished pistons to boot.

    Now look at the RPM where these were rated!

    5,200 RPM in some cases....... 5,400 RPM in some!!!!!

    Who operates their cruiser SBC @ 5,200?

    I'd want to look at the PRM where the previous 260 hp 5.7L was rated.

    Leave a comment:


  • captharv
    replied
    In 1988, 5.7s rated at 260 HP had quadrajets. They may not be the best marine carb going, however, a simple carb change will not increase the HP THAT much. Theres also a performance/cost ratio.

    As far as the open exhausts are concerned, hear this:

    The engine is tuned for the underwater exhaust. While its possible to add the loud and obnoxious open exhausts, you would have to re-jet the carb, and really play with the distributor advance.

    A thought here.......

    The 1988 mercs had the thunderbolt IV system. The newer merc use teh t-bolt V. The diffreence is a knock monitoring system which increases the timing until the motor kn ocks and then backs it off ubtil it just stops. This is the optimal timing for any situation. The 5.7 with tbolt IV and a 2 BBL is rated at 230 HP. The 5.7 with a t bolt V and a 2bl is rated 250. If, by converting to the t-bolt V you can get a 20-25 HP increase, and BTW, also reduces fuel burn, it may be worth the cost.

    What you would need:

    The t-bolt V modules.

    A knock sensor and the mount ( right side engine drain thingie is where its mounted)

    some wiring fron teh sensor to the module.

    It should be a screwdriver and wrench installation.

    The coil and distributor sensor are the same ( and don't screw with them)

    Leave a comment:

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