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  1. Member
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    #21
    Mercury and all other manufacturers rate the horsepower at the propshaft not the power head like some people do. The manufacturers have to stay within 10% of what ever horsepower the motor is sold as. A 300 hp motor for example can be From 270hp-330 hp from the manufacturer, anymore horsepower than that Mercury would have to sell the motor as a 325hp or 350 hp motor. So that being said it should be pretty easy for Mercury to come out with higher horsepower motors now using the V8 platform...rev limiter/fuel curve changes and (or) supercharged. The 250xs was around 270hp, the 300 PM was around 285hp, the 300x and the 2.5L 300 Drag are around 330 hp, the 280 2.5L is around 285 hp. The new 300V8 is around 330 hp. Mercury isn’t going to release anything to the public that is pushing the edge of dependability especially on a brand new motor/platform. Big things to come in the future.
    Last edited by Nichols; 01-01-2019 at 10:23 AM.

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    #22
    Where are you getting the new 300V8 makes 330hp and are still pulling to 6400? The corrected certified numbers are 296hp@5500 for the 300hp non R model and 316hp@6250 for the 300R which has shorter intake runners and different intake cam to allow higher peaks as seen below. My understanding is the 3.2L 300XS 2-stroke that it replaced made right in between them at 306hp. Torque is for holeshot/acceleration and hp is what is needed for top speed, you "gear" a boat with the prop to be at the peak hp for the highest terminal velocity(aero and hydro dynamically drag limited) Raising the limiter is going to shorten the life of an engine which would mean they couldn't offer the same warranty on the "racing" models as they do now unlike in the past.
    http://www.bbcboards.net/showthread.php?t=941852
    Happy New Year to all!

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    #23
    I was told that from from Mercury when we were at Lake X testing the 300R. I gained speed and it kept pulling all the way to 6400 rpms until the rev limiter kicked in. I was also told it was putting out around 330 hp and by the speeds I ran I believe what they told me. A 300xs wouldn’t have run the speeds I ran and I truly believe there is more than 10 hp (1-1.5 mph) difference between a 300xs and a 300R. I would say there is a 25 hp (3-4 mph) difference between the 300xs and the 300R. We are only talking about 150 rpms (6250-6400 rpms)and 14 horsepower(1.5-2 mph).
    Last edited by Nichols; 01-01-2019 at 02:06 PM.

  4. Member esdbass's Avatar
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    #24
    Quote Originally Posted by Nichols View Post
    Mercury and all other manufacturers rate the horsepower at the propshaft not the power head like some people do. The manufacturers have to stay within 10% of what ever horsepower the motor is sold as. A 300 hp motor for example can be From 270hp-330 hp from the manufacturer, anymore horsepower than that Mercury would have to sell the motor as a 325hp or 350 hp motor. So that being said it should be pretty easy for Mercury to come out with higher horsepower motors now using the V8 platform...rev limiter/fuel curve changes and (or) supercharged. The 250xs was around 270hp, the 300 PM was around 285hp, the 300x and the 2.5L 300 Drag are around 330 hp, the 280 2.5L is around 285 hp. The new 300V8 is around 330 hp. Mercury isn’t going to release anything to the public that is pushing the edge of dependability especially on a brand new motor/platform. Big things to come in the future.
    Paul, thanks again for the additional feedback. I wasn't questioning "where" they measured the motors relative to the Power head or the prop shaft but at what point on the HP/Torque curve? So based on you answer I assume, it's just peak HP at the prop shaft.

    It sounds like your saying by your experience and feel that the 300R and a 300X are about the same HP, but obviously the torque of the 300R is much greater.

    I agree Mercury isn't going to release anything to the public that is pushing the edge of dependability and I think this new V8 platform will be just like the 3L 250XS in that for a year or two the RPM's will remain conservative and then they will increase the rev limit. ( I understand you when you said if they increased the rev limit and the 300R or 250R made more than 10% more HP they would have to then sell it as a 325 or 350 in the case of the 300R BUT in 2003 and 2004, the 250XS was limited to 5800 RPM but in 2005 the same motor received 6300 RPM limit. That's 500 more RPM and I'm assuming the same would hold true now with a 250R or a 300R so why was it "OK" then but not now? ( One caveat,I agree 100% that the XS motors do not build any HP much after 6000 RPM probably 6100 being the tops then they start falling off, so I'm assuming the rev limit increase back then just gave more "proping options" not that much of an actual HP gain??? I still think that when the 03 and 04 were increased in 2005 to 6300 there was a HP gain in the first 200-300 RPM.

  5. Banned
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    #25
    Quote Originally Posted by Nichols View Post
    I was told that from from Mercury when we were at Lake X testing the 300R. I gained speed and it kept pulling all the way to 6400 rpms until the rev limiter kicked in. I was also told it was putting out around 330 hp and by the speeds I ran I believe what they told me. A 300xs wouldn’t have run the speeds I ran and I truly believe there is more than 10 hp (1-1.5 mph) difference between a 300xs and a 300R. I would say there is a 25 hp (3-4 mph) difference between the 300xs and the 300R. We are only talking about 150 rpms (6250-6400 rpms)and 14 horsepower(1.5-2 mph).
    Gotcha, not questioning your experience and appreciate the input as trying to learn all I can about these new beasts before making a selection. I assumed initially the 300R was pushing the 10% envelope though Basscat said they tested the same Eyra with both a 300hp pro XS and 300R both with sportmasters and didn't seem to notice a big enough difference worth mentioning. I find it interesting how a 250pro XS, 250R and 300hp seapro all make the same hp.
    http://www.bbcboards.net/showthread.php?t=935367

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    #26
    Quote Originally Posted by esdbass View Post
    Paul, thanks again for the additional feedback. I wasn't questioning "where" they measured the motors relative to the Power head or the prop shaft but at what point on the HP/Torque curve? So based on you answer I assume, it's just peak HP at the prop shaft.

    It sounds like your saying by your experience and feel that the 300R and a 300X are about the same HP, but obviously the torque of the 300R is much greater.

    I agree Mercury isn't going to release anything to the public that is pushing the edge of dependability and I think this new V8 platform will be just like the 3L 250XS in that for a year or two the RPM's will remain conservative and then they will increase the rev limit. ( I understand you when you said if they increased the rev limit and the 300R or 250R made more than 10% more HP they would have to then sell it as a 325 or 350 in the case of the 300R BUT in 2003 and 2004, the 250XS was limited to 5800 RPM but in 2005 the same motor received 6300 RPM limit. That's 500 more RPM and I'm assuming the same would hold true now with a 250R or a 300R so why was it "OK" then but not now? ( One caveat,I agree 100% that the XS motors do not build any HP much after 6000 RPM probably 6100 being the tops then they start falling off, so I'm assuming the rev limit increase back then just gave more "proping options" not that much of an actual HP gain??? I still think that when the 03 and 04 were increased in 2005 to 6300 there was a HP gain in the first 200-300 RPM.
    One thing about the new engines is power can easily be limited by the electronic throttle body controlling the airflow vs older cable operated ones that peak power may have been limited by rpm as the engine is going make however much air it can ingest.

  7. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #27
    Quote Originally Posted by Wheelman View Post
    Where are you getting the new 300V8 makes 330hp and are still pulling to 6400? The corrected certified numbers are 296hp@5500 for the 300hp non R model and 316hp@6250 for the 300R which has shorter intake runners and different intake cam to allow higher peaks as seen below. My understanding is the 3.2L 300XS 2-stroke that it replaced made right in between them at 306hp. Torque is for holeshot/acceleration and hp is what is needed for top speed, you "gear" a boat with the prop to be at the peak hp for the highest terminal velocity(aero and hydro dynamically drag limited) Raising the limiter is going to shorten the life of an engine which would mean they couldn't offer the same warranty on the "racing" models as they do now unlike in the past.
    http://www.bbcboards.net/showthread.php?t=941852
    Happy New Year to all!
    Keep in mind: As you're aware, the numbers you are quoting are CARB numbers, essentially registration information that was provided with the Emissions Certifications for the specific engine model.

    Those numbers would most commonly come from an engine running in a controlled environment, and often do not show outputs at the maximum RPM's of the engine. This is why the constant "quoting" of CARB report numbers is becoming a problem (much the same as the quoting of 3rd and 4th party "weight discrepancy" stories).

    While this isn't the Mercury Forums- it's good to note that it's been an ongoing problem there.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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    #28
    Quote Originally Posted by EuropeanAM View Post
    Keep in mind: As you're aware, the numbers you are quoting are CARB numbers, essentially registration information that was provided with the Emissions Certifications for the specific engine model.

    Those numbers would most commonly come from an engine running in a controlled environment, and often do not show outputs at the maximum RPM's of the engine. This is why the constant "quoting" of CARB report numbers is becoming a problem (much the same as the quoting of 3rd and 4th party "weight discrepancy" stories).

    While this isn't the Mercury Forums- it's good to note that it's been an ongoing problem there.
    The numbers in the CARB report are given by the manufacturer correct? They are numbers corrected to some atmospheric condition like I asked in the other thread as I wasn't sure whether or not it was the same as the automotive SAE standard. Do you have some better way to compare them other than some sticker on the cowling?

  9. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #29
    The best comparison is an actual owned/rigged and broken in engine, run on a propshaft dyno at specified WOT RPM's. THAT data might be worth quoting.

    For most guys (certainly the ones in this forum) they're interested in how big of a wheel they can spin, at how low of a slip number, and the best WOT RPM's they can turn. Even dyno data isn't necessary reflective of real world performance.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

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