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    How shallow should I run my drive?Bravo-->TRS (now)--->option for Konrad later...
    #1
    I bought a 24' Mariah without drive/power. Single engine at this time...

    I'll be running ~450hp with a TH400 set up as a two speed--- and am making an extension box to convert from bravo to TRS and to able to run the prop a bit shallower--- TRS is tall! 1.46 trans ratio 1.50 drive ratio --- I hope that with a ~65mph prop on it, that I can pull tube/wakeboard or putt around 2nd gear without lugging the motor, and can air it out in 1:1 without needing to change props as I have in the past with boats that don't have two gears. Extension box I think will be in the 7" range but I can build it back there even further if needed.

    What height should I set the prop at? I think it would be safe if I don't find better information to put it ~2" above (shallower) where the bravo had it---- and if I get into more power and need a konrad later, could lift it a bit further at that time with the shorter konrad.

    All feedback appreciated!!! Thank you.
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    #2
    Founding Member / Super Moderator Ratickle's Avatar
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    Wow, what an extreme project.

    A couple questions first;

    Why are you switching to a TRS from a Bravo? TRS's are obsolete, no parts available. Pretty much the same thing with Konrads. Only used parts, or some new internal parts, are available out there. Aftermarket Bravo's, or the latest Bravo One XR's, are good to over 600 HP. About the same as a TRS.

    Also, the TRS is a slower drive for top speed because of the size of the bullet and leg. Let alone, it weighs more.

    I also don't believe there is any reason you would need a transmission to give you a lower gear. A 24 Mariah, with 450 HP, is gonna jump on plane with a 1.5 ratio drive. The only reason to use a trans with a lower gear, in my mind, is if you are going to use a really tall drive ratio and would need a lower gear to get on plane with a full, heavier, boat. (Or a turbo diesel).

    As for the extension box. Some say 1/2" higher for every 3" of extension. So 2" per foot. But every boat is different due to bottom design. If you really decide to go this way, I can check with the V Lite guys who have tested every extension box available. 7", 9", and 12". Their testing would be on a single engine deep-vee single.

    Personally, I would not consider what you are considering without a really good reason.
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    #3
    Quote Originally Posted by Ratickle View Post
    Wow, what an extreme project.

    A couple questions first;

    Why are you switching to a TRS from a Bravo? TRS's are obsolete, no parts available. Pretty much the same thing with Konrads. Only used parts, or some new internal parts, are available out there. Aftermarket Bravo's, or the latest Bravo One XR's, are good to over 600 HP. About the same as a TRS.

    Also, the TRS is a slower drive for top speed because of the size of the bullet and leg. Let alone, it weighs more.

    I also don't believe there is any reason you would need a transmission to give you a lower gear. A 24 Mariah, with 450 HP, is gonna jump on plane with a 1.5 ratio drive. The only reason to use a trans with a lower gear, in my mind, is if you are going to use a really tall drive ratio and would need a lower gear to get on plane with a full, heavier, boat. (Or a turbo diesel).

    As for the extension box. Some say 1/2" higher for every 3" of extension. So 2" per foot. But every boat is different due to bottom design. If you really decide to go this way, I can check with the V Lite guys who have tested every extension box available. 7", 9", and 12". Their testing would be on a single engine deep-vee single.

    Personally, I would not consider what you are considering without a really good reason.
    Excellent information, and I agree, it's a big change and usually wouldn't be warranted. Some part of it is wanting to try things, and what most say they end up with after extension boxes seem to be some good advantages---- besides me needing it to fit the longer drivetrain in. Please check with the V lite guys and see what they found. If at ~9" back it would need to be in the ~1.5" range, and likely could have come up 1/2" over the bravo anyways, that's a somewhat easy number to aim for.

    What makes a konrad obsolete now---- no individual parts availability?

    If I had a bravo already---- it'd be on the water and I'd be planning what to do when it breaks $$$$$. I'm $1000 into having three complete TRS setups and suspect I can sell some of the extra parts for enough to cover the materials for the extension box, TH400 coupler, and part of the hydraulic steering upgrade. While I plan for ~450hp, it might be lacking greatly in low end torque compared to most 450hp marine engines---- With 1.46X1.50 gear ratio, that's not going to matter out of the hole. With fully jacketed exhaust for as long of a length as I can fabricate, I can also cam it to the point of not worrying about torque at 2500rpm, or reversion/water ingestion.

    Spending a bit of time around boats with transmissions. They are soooo smooth... Lumpy sounding cam and 1300rpm idle? Transmission still doesn't care.
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    #4
    Founding Member / Super Moderator Ratickle's Avatar
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    A good Bravo would not break. I bet, with 3 good TRS's you could get enough for them to pay for a good Bravo.

    IMCO's 12" standoff box actually comes up to a 3" lift built into the box, if that tells you anything about maximum height over stock.

    Are you running a small block with higher RPM? Is that the reason you're worried about torque?
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    #5
    Founding Member / Super Moderator Ratickle's Avatar
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    And yes, transmissions boats are smooth compared to Bravo boats.

    Mercury itself says their XR is rated for up to 600 HP. They put it behind the 565 with full warranty.
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    #6
    Founding Member / Super Moderator Ratickle's Avatar
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    Well, I shouldn't spread rumors, let me check.

    The rumors are that Konrad quit making the 540 PRS and 540 PRSIII. I don't know that for sure. Those were the ones that were bolt-on replacements for the TRS and Speedmaster III's.

    I will check for sure.
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    #7
    Yes, small block power. If I don't get into a second boat with twin power, I'll want to turn this one up to ~550hp or more. I'm making enough space with the extension box for BBC+TH400 from the start although with more torque I wouldn't necessarily use another gear so I'll hang onto one velvet drive.

    I figure if I'm at a point that a TRS ALSO doesn't break... I have 5+ years worth of parts already for them? If I didn't break an XR or other bravo but did wear it to needing refresh some parts in it at year 3, where does that $$$ put me?
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    #8
    Founding Member / Super Moderator Ratickle's Avatar
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    Jimmy Speros, Mobilemercman, needs to get on here. He knows a lot more than me on this stuff.

    My next question, is with the additional weight at the back of the boat, will it be stern heavy and handle rough water like crap. TRS is heavier than a Bravo, extension box sets it back farther than stock Bravo, transmission is additional weight, etc.

    He may have tested/tried something similar.

    Plus, he has raised the TRS's on his Fountain and knows a ton about TRS's versus Bravo's for cost, strength, availability, etc.

    Take a look at his Lucky thread. http://seriousoffshore.com/forums/sh...ighlight=lucky

    Post 202 is old drive height versus new
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    #9
    Quote Originally Posted by Ratickle View Post
    Jimmy Speros, Mobilemercman, needs to get on here. He knows a lot more than me on this stuff.

    My next question, is with the additional weight at the back of the boat, will it be stern heavy and handle rough water like crap. TRS is heavier than a Bravo, extension box sets it back farther than stock Bravo, transmission is additional weight, etc.

    He may have tested/tried something similar.

    Plus, he has raised the TRS's on his Fountain and knows a ton about TRS's versus Bravo's for cost, strength, availability, etc.

    Take a look at his Lucky thread. http://seriousoffshore.com/forums/sh...ighlight=lucky

    Post 202 is old drive height versus new
    It looks like he has given them a work out, for sure!!!!

    I'll very very rarely see rough water---(Haven't done LOTO in my own boat yet but plan to with this one maybe 1x/year) but agree that I'm conscious of the weight and where it is . I see where I can trim a bit of weight on the exhaust. I plan to be the backwards (exhaust) 1/2 fresh water cooled season 1 (more weight) but then full fresh water cooled so I feel better about going to aluminum block/heads season 2. I will have heat exchanger, batteries, trim pump all mounted forward as far as is sensible.
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    #10
    Founding Member / Super Moderator Ratickle's Avatar
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    I've got to say, I'm still a believer that you're gonna have a mess.

    Think if it this way:

    Small or large block, made no difference, with a TRS the engine was set forward around a foot (transmission) and had the heavy TRS drive bolted to the transom. CG was similar to a Bravo where the engine connected at the transom with no transmission.

    You are considering having the transmission in a setback box, and the TRS behind that. I think it would handle the same as if you had a fat chick sitting on the swim platform.

    But, if you are serious, the drive going to need to be raised somewhere in that range above.

    Also, I just got off the phone with the guys at Konrad. They have all of the parts to build the drives. They just don't keep assembled ones on the shelf any longer.

    They said 3 to 4 weeks lead time for a complete assembly.
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    #11
    Founding Member / Super Moderator Ratickle's Avatar
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    How are you planning on connecting the transmission to the drive?

    A custom coupler?
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    #12
    From the transom forward, it should be similar weighted as if it had a big block, I should have maximum of ~3.5" of the transmission poking past the transom. Velvet drive would have poked through about ~1/2" by my measurements.

    I'll have a shaft made with a u joint at one end for the trans slip joke, or flat flange/cv (not decided yet) and the other end will be the same u joint as the start of the double cardan of the original velvet drive to TRS input shaft.
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    #13
    Founding Member / Competitor MOBILEMERCMAN's Avatar
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    Save your self a ton of time, effort and, trial and error and just re assemble the boat the way it was with a bravo.
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    #14
    I certainly have more time than money--- and I do like fabricating... We'll see if it turns out I have as much sense

    If good usable bravo drives were about half the cost they currently are..... I could see going that route.
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    #15
    Founding Member / Competitor MOBILEMERCMAN's Avatar
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    The issue that immediately comes to mind is you are drastically altering the balance of the boat and I don't think you have thought through how to carry the load of the end of the transmission or figured out how to align the entire creation. A TRS engine is aligned to the bellhousing of the transom assembly. The tailshaft bearing supports the input shaft from drive and the entire engine transmission package floats thru the transom. On a Bravo the gimble bearing is supported, actually held firm in the transom, the transom carries the rear of the engine and you align the engine with that bearing. It is much easier to rig a bravo engine package.

    Fabricating and engineering are different things.
    Last edited by MOBILEMERCMAN; 08-02-2018 at 10:21 PM.
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    #16
    Founding Member / Competitor MOBILEMERCMAN's Avatar
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    Here is an alignment tool sticking out of the trannie the silver disc aligns to the bellhousing on transom assembly where drive mounts. Click image for larger version. 

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    #17
    Founding Member / Super Moderator Ratickle's Avatar
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    Quote Originally Posted by Faster7 View Post
    I certainly have more time than money--- and I do like fabricating... We'll see if it turns out I have as much sense

    If good usable bravo drives were about half the cost they currently are..... I could see going that route.
    I believe that good, remanufactured, Bravo drives are less than $4000 on Ebay currently. I also believe, if your 3 TRS's are in good shape (meaning not saltwater use and no twisted shafts), they are worth over $1000 each or more.

    I think the difference you will spend doing your rerig will be more than that, especially if you count your time as worth anything. And, it may not work and you will be rerigging it back with a Bravo.

    Think about it carefully.
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    #18
    Founding Member / Super Moderator Ratickle's Avatar
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    Oh, I still think the boat will jump on plane with a 450 HP small block. Think about how many boats are out there like yours, 24' Vee's, with HP ranges between single 260 small blocks with Alpha's to single 330 big blocks with Bravo's.

    Your 450 HP small block should have more torque than a 330 HP big block. And, weigh less.

    I'm assuming you're planning on making your 450 HP at no more than 6000 RPM.
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    #19
    Yes, no need to pass 6000rpm. If it had to idle nice to make a bravo/etc shift gently it'd maybe give up say 40hp@6000 and 30 @5000.

    I know I'll have to watch alignment, but if it's a double cardan/ CV at the front of the shaft the same as what's stock at the rear of the shaft, it won't be super critical.

    I absolutely agree that I will have a bunch of time in this. I'd be spending time on other projects with my dad if at all possible if it wasn't this one.
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    #20
    Founding Member / Super Moderator Ratickle's Avatar
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    You will definitely have a bunch of time in it.

    Well, if you're proceeding, we will definitely be interested in following along and trying to help with any issues you run into.

    Best of luck.
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