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  1. #1

    Verado 350 Sci vs Optimax 300XS - which is fastest?


    I have a Phantom 25 with twin Merc 2.5 EFI SS engines. Due to gas - and maintainance costs I seriously consider to step down to a single engine again. I used to have a Promax 300 with an SVS for 9 years.

    The boat dry weight is approx. 800 kilos without engines, gas and driver. It likes to have weight aft due to balance. Twin 2.5 EFI balance out very well.

    The weight of the Optimax 300XS is 229 kilos and Verado 350 Sci is 308 kilos. However, you have to add the hydraulic steering to the 300 XS. I personaly do not think the extra 60 kilos aft mean so much. I may step down 2 inches of setback to 5,5 inches, instead of 7,5 inches which I ran with the Promax 300.

    I have checked out the fuel consumption, and they are running both approx. 40 litre / 10 gallon per hour at 4,000 rpms. The Verado does not need more than 7 litre oil per season, the Optimax 300 XS need 2% oil.

    The big question is speed; which of the two will be fastest? According to a owner of both his 24 feet centre console was 5 mph faster with the Verado 350 Sci than with the Optimax 300 XS. The Optimax 300 XS was 1 mph faster than the Verado 300 on his boat.

    The Verado 350 Sci is an expensive engine, but if the package is 5-6 mph faster than my old Promax 300, it will be well worth the money. I will then break the 80 mph barrier with a single engine (81-82 mph in fact).

    What do you think?

    Cheers and thanks, Toffen G

  2. #2
    Verado 350 Sci
    06 Daytona 27'
    600 Cubic
    Whipple 8.3

  3. #3
    If you don't mind the extra cost of the engine go for the 350 Sci. I would also assume that overall consumption will be higher with the Verado.
    ~Outboard Maniac~

  4. #4
    My understanding is that the 4 stroke is more economical at lower RPMS and the 300XS would be as economical as you go to higher RPMS.
    I had a friend with a 25 phantom that ran twins and then switched to a single. With the twins the boat ran well and drove great with the single it handled poorly and was nothing like the twin. It may have been his set up but I would try to find someone that has run the phantom with a big single and see what they found. I always thought it was a great boat with twins.

  5. #5
    Join Date
    Jan 2006
    Performance Marine, Lake George NY
    Verado 375 will be out soon
    Johnny Saris
    Driver-441 32 Cobra
    Saris Racing Engines
    World Champions 2013, 2014

  6. #6

    Verado 350 sci vs Optimax 300XS


    I used to have a single Promax 300 on the Phantom 25 from 1999 until 2006. Before that the boat was equipped with a Johnson 3,6 litre V8 300 hp engine. A big beast for that time. Although the boat is more stable with twins spinning out, a single engine works great in my opinion. Ofcourse, the verado 350 Sci is heavier than both the Johnson 3,6 and Promax 300. I used a CMC powerlift with the Promax 300 and 7,5 inch setback. I may have to go down to 5,5 inch setback.

    Do you anyone of you know if the Verado 350 Sci can be delivered with a lower unit with a torque tab ala torque master. Or is it only delivered with a straight skeg ala Fleetmaster? I want to avoid the crabbing effect loosing speed at wot.

    Cheeers, ToffenG

  7. #7
    I know that Merc Racing has developed a completely new lower unit for the 350 SCi, but I don't know about the skeg. As it is a HP unit, I am leaning towards the idea that it would have a torque tab.

    When you decide let us know the results
    ~Outboard Maniac~

  8. #8

    I phoned Mercury Racing and weird enough they do not offer a torque master like lower unit. Only straight skeg. Would a torque tamer do the work? Will it increase speed?

    I used to have a torquemaster lower unit on my Promax 300. Before that I had a fleetmaster straight skeg lower unit. Due to internals breaking I swopped to a torquemaster lower unit. I obtained the same speed though.

    Cheeers, ToffenG

  9. #9
    Join Date
    Aug 2004
    Venice, Florida
    The Verado 350 weighs about 160 pounds more than the 300XS. It also has a larger gearcase which means more drag. The gearcase changed from the prototypes to a larger gearcase in the produvtion motors. Performance with the early prototypes was better than the production units. There has been a big center console speed war going and the fastest to date is a 38 Fountain with 4 300XS motors that ran a tick over 87mph. There is another 38 Fountain with 4 350SCI motors that cant break 83mph. Depending on how your boat handles the extra weight, the 300XS is probably faster.
    Cool and Unique Boating and Fishing Products

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  10. #10


    Is there any engine mods to be done to the Optimax 300XS to increase horsepower?

    If you compare an Optimax 300XS with a PM 300 (1999 model) with a SVS, how much gain can be expected with the Optimax 300XS?

    Cheeers! ToffenG
    Last edited by Toffen; 07-27-2009 at 03:32 PM.

  11. #11

    Increase hp on Mercury 300XS

    Gain an additional 35-40 hp on the Mercury 300XS by lightening the flywheel and remapping the ECU. Solid, reliable performance.

  12. #12
    Join Date
    Sep 2008
    Treasure Island Fl
    38 fountain will do 82 with 3 350 verados and will do 78 with 3 300 xs and 75 with 3 300 verados.

  13. #13
    Quote Originally Posted by native2 View Post
    38 fountain will do 82 with 3 350 verados and will do 78 with 3 300 xs and 75 with 3 300 verados.

  14. #14


    Quote Originally Posted by Skytour View Post
    Gain an additional 35-40 hp on the Mercury 300XS by lightening the flywheel and remapping the ECU. Solid, reliable performance.
    does this realy work? is it reliable? whats the gain? i own a fountain 27ft open fish with twin 300xs 07, running 75 mph at 5850 rpm 25 inch fleetmaster lowers,6% slip on a bracket turing labed mirage props 25 pitch

  15. #15

    Simon Motosports Mods

    The flywheel lightening and ECU remapping work very well. The Mercury flywheel is overbuilt (heavy) and the engine benefits from the lighter flywheel. The ECU remapping improves combustion and they also raise the rpm limiter. I have mine set at 6100 rpm although it can be as high as 6800. These engines produce more HP with any increase in rpm. I've had both my engines modified. Took about 30 minutes per engine to remove the flywheel and ECU. Less than a week turn around including shipping (Priority Mail). Substantial improvement in hole shot and throttle response. Only downside is that I had to buy new props to take advantage of the new rpm limit but I wanted to buy new 4-blade offshore props anyway.

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