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  1. #1
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    Going from 250 2 stroke to 250 4 stroke

    I sold my pro xs 250 2 stroke and I'm repowering with the pro xs 4 stroke. The question I got is what do I need(if anything) to make the swap? Are controls and guages the same. Just trying to see what I need

  2. Member
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    #2
    Go down about 1/2 page to the 2 stroke to 4 stroke repower post.
    Rick Collis
    903-473-8820

  3. Member fishnfireman's Avatar
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    #3
    Here's a list Don gave.
    -Keyswitch Extension Harness (must be 5' longer, usually 10' extension to keep connections in bildge)
    -Prop of AT LEAST 1" lower pitch
    -New Mounting Hardware (suggest OEM kit)
    -New 3/8" Fuel Line from tank to engine (NO BULB)
    -Rigging Hose Kit
    -975 CCA (MINIMUM) AGM Battery Required. Recommend higher if possible.
    -Inspect all other rigging for wear/tear and address as required.
    (While you may need other incidental items, the above are the most commonly needed for this type of repower).

    I'm in the same (boat) as you.. new mtr comming in a couple days before I leave for a big championship tournament, so I'm trying to be as prepared as possible with everyone's help.
    If you are getting the mechanical control model your cables should work, however the shifter, throttle and battery cables are located different than a 2 stroke.. Have heard of a couple who needed longer cables.
    I was told the new rigging tube and motor flange are a smaller diameter.
    Your gauges will be dependent on what kind is in your boat..
    Depending on what gears you are running in the 2 stroke your prop may be fine, as I believe all the V8's have 175-1 gears

  4. mikesxpress
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    #4
    Tips to go to a CMS 250 V8:
    1. Don't get a harness extension. Most rigs have enough slack inside the boat to reach the plug on the back of the V8. My Ranger did.
    2. The grommet on the engine only allows for required cables/hose. For those with a Hot Foot used on the Opti's standard practice was to leave the shifter throttle cable in the rigging tube and lay loose inside the lower pan cowl. You can't do that with the V8. Either disconnect & remove or pull it into the service well and secure.
    3. If you have a Level 1 Merc Monitor and want to see your water pressure displayed you will need to add the sensor.
    4. Be prepared to add another rigging hole for the new tube/flange. This tube used for just engine operational cables/fuel line. I used the existing draw tite flange for my PP lines and ducer cables.
    5. You can ditch the oil tank and gain some room in the service well.
    6. Run new 3/8" fuel line to your tank(s).
    7. Ensure your Hot Foot travel is set for demand/demand linear (idle to full throttle) with the laptop. You can't do this yourself.
    8. Ensure your trim range is set properly. The V8 dims change your prop to pad distance drastically from the Opti. It did on my repower.
    9. This V8 can spin up to 6200 rpms and it needs to run as close to that as possible. The 1 pitch prop drop doesn't work for most. I was turning a 25P Tempest + with 2 medium plugs and one hole open on the Opti to get 6000 rpms. The best performing prop on the V8 in my summer time application is a 23P Fury with all holes plugged (the V8 doesn't really utilize the PVS like the Opti did). 6150 - 6200 rpms. Winter I use a 24P Fury to knock the enhanced cool weather rpms back down to 6150.

    I'm sure I am leaving out a few additional things but will add them later. Having dealt with the repower transition since 7/31/18 and being involved with the rigging and subsequent learning curve/adjustments, I can say that you have to re-learn almost everything about your boat operation. Hyd jack plate settings, trim, etc.. all changed.

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    #5
    Witch Merc monitors will work’ when doing the Re power ?..

  6. Member fishnfireman's Avatar
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    #6
    All this talk of using lower pitch props is not sounding good.
    After talking to those in the Allison camp who have switched. If the 250R wont put my rig in the upper 80's with my 30 pro max it will be for sale.

  7. mikesxpress
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    #7
    Mike I'm not sure how the 250R will react prop wise on the lighter weight Ali. The more heavy standard bass rigs like a Ranger, Phoenix, etc.. all see the pitch drop. What do the Ali guys say that already have one?

  8. Member fishnfireman's Avatar
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    #8
    theres some good reports on the Allison page.
    Most are just loving it. however it took some work to get there. main thing is the new SM LU wants to run considerably higher than the LU of the 2 stroke. that and getting it propped right.
    some are already wanting the taller gears to get off the limiter.

    thats what surprised me -- I figured most everyone who was re-powering from the same HP 2 stroke would have had the 1.62 gears and going to 1.75 would be a wash ?

  9. mikesxpress
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    #9
    1.75 gears standard on CMS V8 250 ProXS repower for an Opti. Mine would not turn the 25P Tempest + over 5700.

  10. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #10
    Keep in mind- a Sportmaster is a whole different animal than the Torquemaster. Probably need to stick with nsd's engine question (and avoid confusing with the many other configurations).

    nsd22002... do you know WHICH 250 you're getting, and what it's going on?


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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  11. Member GLOCKMEISTER's Avatar
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    #11
    Not trying to hijack, but this seems related. I’m having issues getting WOT on my 300r. Was told by a few folks a HotFoot upgrade was needed. T&H said I needed the Top Load
    HF-1T-DP

    My old hotfoot is at least 10 years old, anyone familiar with that?
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  12. Member fishnfireman's Avatar
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    #12
    Are you checking for full throttle on the computer ?

  13. Member idratherbeefishin's Avatar
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    #13
    Quote Originally Posted by birdman920 View Post
    Witch Merc monitors will work’ when doing the Re power ?..
    Suggest level one should give u most engine readouts you will need. Oil pressure, oil temperature, water pressure, RPMs, fuel consumption, as stated above water pressure sensor will be needed to be purchased in order to have that read out

  14. mikesxpress
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    #14
    Quote Originally Posted by GLOCKMEISTER View Post
    Not trying to hijack, but this seems related. I’m having issues getting WOT on my 300r. Was told by a few folks a HotFoot upgrade was needed. T&H said I needed the Top Load
    HF-1T-DP

    My old hotfoot is at least 10 years old, anyone familiar with that?
    Phillip I have a 2009 hot foot in my Ranger and it functions properly with the new CMS 4.6L 250 V8. The demand/demand linear (idle to WOT) is set during rigging with a combination of the laptop and hot foot adjustments. That simple. If your not getting WOT then the dealer that rigged your engine is the issue, not the hot foot. As far as what folks told you, they obviously haven't any personal experience with a CMS repower from an Opti. As far as TH goes, they are trying to sell you stuff you don't need.

  15. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #15
    Quote Originally Posted by mikesxpress View Post
    Phillip I have a 2009 hot foot in my Ranger and it functions properly with the new CMS 4.6L 250 V8. The demand/demand linear (idle to WOT) is set during rigging with a combination of the laptop and hot foot adjustments. That simple. If your not getting WOT then the dealer that rigged your engine is the issue, not the hot foot. As far as what folks told you, they obviously haven't any personal experience with a CMS repower from an Opti. As far as TH goes, they are trying to sell you stuff you don't need.
    +1... no reason you cannot use the one you have (unless it's worn and no longer serviceable). You may want to consider a new cable, if yours hasn't been upgraded to the later design cables (not talking "generation"... but actual cable DESIGN that is far smoother with less binding/resistance).


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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  16. Member fishnfireman's Avatar
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    #16
    Quote Originally Posted by fishnfireman View Post
    All this talk of using lower pitch props is not sounding good.
    After talking to those in the Allison camp who have switched. If the 250R wont put my rig in the upper 80's with my 30 pro max it will be for sale.
    Follow up.
    Same 30 pitch pro max. By seat of pants the 250R will out pull the 300 XS.
    Can't compare top end yet as I still can't raise engine high enough for the redesigned SM LU.
    My next project.

  17. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #17
    Be sure to update with your final results. Just make sure you get that new engine up there near the top of the recommended WOT RPM range (fully loaded).


    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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  18. Member fishnfireman's Avatar
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    #18
    Yes sir.
    If the 30 won't get on the limiter I have a 28 .

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    #19
    I’ve heard mention a new hotfoot is required ?

  20. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #20
    No... though SOME top-feed hotfoot models may require modification (and ALL hotfoot models will require a little extra setup).


    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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