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Thread: Racing exhaust for laker 49 OMC

  1. #71
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    Default OMC 49.9 exhaust progress

    Here is the completed exhaust system ready for production. The introductory price is $495 which includes the 6061-T6 divider plate & water jacket, 355 casting, gaskets, and fasteners ready for assembly (plus shipping). Orders for the first run will be taken through April 10 and require a $250 deposit. Shipments will be early-mid May. Please PM your contact information to reserve your system. Thanks for your interest.

    Tim
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  2. #72
    Team Member 850cc racer's Avatar
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    Hey Tim,

    could you please let me know how far the outer cover sits out from the block?

    wondering if it would sit under our sst60 style cowls.

    Cheers

    Rob

  3. #73
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    Default Under the cowl

    The system as shown is exactly 3" measured from the exhaust face of your 49.9 block including gaskets and fasteners. This is about .090" deeper than the OMC factory Mod-50exhaust system. It should just fit under the Stinger and SST-60 cowls.

    Tim

  4. #74
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    Based on .090 it will fit for SURE under both. Had a Mod 50 under a standard Stinger cowl and that fit with NO issues... Looks real good Tim !!!!


    Todd

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    Default Performance ?

    Expected Performance Gains ?

    Would this help also ?

    Dimensions ?
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  6. #76
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    Default Pipe tuning

    The custom longer tuner shown will add bottom and mid-range to the 49.9. It would be helpful when running a fully immeresed propellers, or in drag race applicaitons where out of the hole performance is desired. Note that top end will be adversely affected.

    With high propshaft positions used in hight speed and/or racing applications, there's enough slip to get the boat on plane and into the higher range powerband provided by the short interconnects offerer with the Mod-50 style exhaust system.

    Thanks to Thom for clarifying the ability to fit my "laker" exhaust under factory cowlings. Nobody will suspect anything until you top end them........

    Tim

  7. #77
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    As thorn asked above...."what are the performance gains?"???? Have there been any test performed on a selected boat, running stock, then your system....any noted results/???
    Any HP dyno test performed? It would seem these would be questions with answers...if favorable, I would be interested in a system...thanks n advance...george in texas

  8. #78
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    Default Laker exhausts

    Quote Originally Posted by marchettih2o View Post
    As thorn asked above...."what are the performance gains?"???? Have there been any test performed on a selected boat, running stock, then your system....any noted results/???
    Any HP dyno test performed? It would seem these would be questions with answers...if favorable, I would be interested in a system...thanks n advance...george in texas
    Hey to George, Lawrence, others. I have no dyno testing and don't plan to pull any. The improved Nydahl is a close copy of the OMC Mod-50 exhaust system.

    That factory race engines used close interconnects is self evident proof of the advantages - it raises the usable rev range and horsepower. If you look at the Mod-50 system, the Yamaha copies, and any late model triple or V-6 exhaust you'll see closest possible exhaust port interconnects.

    These systems will be built on a made to order basis only. Orders received on/before April 10 will be delivered late this spring. If you don't order now you'll need to wait until next winter.

    Tim

    PS The planned price went from $450 to $495 for the first run due to complex coring that proved necessary at the casting foundry. The price may change after the first run depending in degree of difficulty in machining.

  9. #79
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    always wondered about the open chest...could we make a better bubble back for the crossflow V4 and V6?

  10. #80
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    Default V4 vs V6

    Be aware the V6 is actually two banks of triples, each with 120 degree firing order spacing. The triple "pulse tuning" phenomenon only works with this configuration (or multiples thereof).

    Twins, fours, and early Merc in-line sixes tuned with 180 degree alternate firing pairs do not get the 120 degree tuning advantage. It should be noted that Mercury later rephased inline six cranks to take advantage of twin stacked triple exhaust tuning.

    The answer to your question is no. Engines with other than 120 degree firing order cannot take advantage of the the simple "open chest" exhaust design.

    Tim

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