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Thread: 270 Volvo duo prop conversion for Corsican

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    270 Volvo duo prop conversion for Corsican

    Hey gang - I am curious about performance with an upgrade to a duo prop with a Volvo 270. It's for my 69 Corsican with 351 Cleveland all upgraded. Currently running a 19 Solas at about 5700 rpm at 55 mph. (Was getting 52 mph at 4400 rpm with 21 Soals.)

    Will my performance be substantially better with duo setup and are there any other issues to consider?

    thx

    -Patrick

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    Quote Originally Posted by bootdaddy View Post
    Hey gang - I am curious about performance with an upgrade to a duo prop with a Volvo 270. It's for my 69 Corsican with 351 Cleveland all upgraded. Currently running a 19 Solas at about 5700 rpm at 55 mph. (Was getting 52 mph at 4400 rpm with 21 Soals.)

    Will my performance be substantially better with duo setup and are there any other issues to consider?

    thx

    -Patrick
    i'm trying to understand the 1300 rpm difference for only a 2" pitch change?
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    I thought it was the 23 Solas (it may be in fact) but the local prop guy says old prop 21 and new prop is 19...

    Not really sure why the big difference in rpm other than it seemed to load the motor and looking at it sure seemed like a big prop for the size boat...

    given power in boat, seem to be missing some speed...or not?! engine buillder said it can run in low 6000s and be ok...

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    something doesn't match up. I'm running a 21 Solas turning it to 4800 rpm, with a stock 260 hp sbc. I tested the solas 19 and it turned about 5200 rpm. I did here something about the early batch of solas 21 props having more pitch than marked though. Griz would have had the answer, Man I miss Griz.
    1978 X-18, SBC, Volvo 280T
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    Prop questions aside ,I'm not sure I got your question right ..

    You said you are curious with an uprgade to a duoprop with a Volvo 270 ...

    There is no 270 duoprop outdrive.
    Do you mean you are considering chucking everything out and going with a new duoprop package ..engine , drive etc ?

    As far as performance benefits go , are you reasonably happy with how your boat runs/handles now and have you tried a d/p setup before ?

    I know that it's very hard to find smaller boats like ours that we can easily compare to that have D/P units .
    Just because something's old doesn't mean you throw it away !

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    I have seen a 16' w/DP and man is that a heavy outdrive on a small boat. I can't rmrmber if it had a 4.3 or a 5.0. When my bud removes a DP or a B3 from a boat he has to do it in 2 sections because of weight. I thought they were for big underpowered boats but I guess they have some benefit. Props are not readily available like regular props, you buy them in sets which makes it REALLY hard to dial them in not to mention REALLY expensive.
    Nick
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    I'm curious on what difference a duo would make or if its even possible. I have the 270 and its in very good shape. My bud just redid his Hiliner w new volvo engine and new duo and mentioned that Wilbert (owner) of French Creek marina has 2 duo prop units for my drive...

    When I spoke to Wilbert today, he considered my question and said he couldn't think of any reason why it couldn't be setup on the 270...

    In one sense the 21 solas was decent but just couldn't get rpm's to hit power band with max rpm 4400 w trim. The 19 is seems right but thought I would have better top end than 3-4 mphs, its better around docks and gets 5700 w trim and the engine sure sounds happier...

    I guess I'm just wondering if I am missing something (as ususal!)? Ha!

    The boat at speed is definitely very fun...lanyard clipped in!

    There are no trim tabs as I wanted to keep it looking as original as possible.

    The other issue is heat...with trim at speed it gets a little over 180 degrees until I pull in trim or reduce throttle...

    Finding the balance of performance with originality...not always easy.

    thx

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    The 290 DP lower should( i have not tried it but alot of the AQ stuff can be interchanged)bolt right up to a 270 upper. Is this a 270 T ???

    finding a matched set of props will be hard to find in the right pitch to let your motor run in it's power band. not sure a DP is gonna like living at 5grand or higher.

    a duo will eliminate hunting when off plane and torque steer while on plane.

    the numbers you posted( if it is a 1.6) on the 19 solas are around 14% slip that is very high slip for a solas . the solas I have run have been at or under 10% slip

    have you GPS'd your numbers? have you confirmed the drive ratio? confirmed the tach? 5700 rpm on a 1.6 with a solas 19 should be 58-59 ish

    once you have reached top end have you tried to lower the trim a tad??
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    Quote Originally Posted by mattyboy View Post
    The 290 DP lower should( i have not tried it but alot of the AQ stuff can be interchanged)bolt right up to a 270 upper. Is this a 270 T ???

    finding a matched set of props will be hard to find in the right pitch to let your motor run in it's power band. not sure a DP is gonna like living at 5grand or higher.

    a duo will eliminate hunting when off plane and torque steer while on plane.

    the numbers you posted( if it is a 1.6) on the 19 solas are around 14% slip that is very high slip for a solas . the solas I have run have been at or under 10% slip

    have you GPS'd your numbers? have you confirmed the drive ratio? confirmed the tach? 5700 rpm on a 1.6 with a solas 19 should be 58-59 ish

    once you have reached top end have you tried to lower the trim a tad??
    Actually, I just downloaded the INavX app on Ipad and going to do that this afternoon to verify speeds...it was initially done pacing new jetski Ha! There is a noce little chop on St Lawrence today to run test.

    Yes 270 T

    Not sure on ratio but have been told that tweaking and labbing prop easiest way to gain a few mph and have to agree when I consider Wilbert wants $4500 for lower and $800 for set of props...he did mention best with a little lower rpm...but then again, not in powerband and lots of $!

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    umm it might be a 270 drive leg but that is a 290 transom housing a 290DP will hook right up and I believe the transom cutout will work for a newer volvo drive/transom assembly as well.

    another thought would be someone hung a 270 lower on 290 setup. with that setup I would really want to confirm the drive ratio before I did anything.
    When the sky is grey,look out to sea.
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    Quote Originally Posted by mattyboy View Post
    umm it might be a 270 drive leg but that is a 290 transom housing a 290DP will hook right up and I believe the transom cutout will work for a newer volvo drive/transom assembly as well.

    another thought would be someone hung a 270 lower on 290 setup. with that setup I would really want to confirm the drive ratio before I did anything.
    thanks Matty - will confirm ratio

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    The DuoProp will really work wonders in terms of handling in all sorts of water conditions, and with single-digit slip numbers it will be more efficient as well, but don't be disappointed when you find that your Corsican is not going any faster than with your single prop AQ270/Solas setup. You are going to need more power to go faster.


    Also, though very similar to the 270, to do a DP conversion I personally would want to first find a good AQ290 type upper and transom. The 290 has integrated trim and tilt, and generally less slop in the gimbal than the earlier Aquamatics. Though the 270t is good, but the 290 upper is just better suited when spending good money on a DP conversion.

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    Beautiful set up. Very tight engine compartment.

    I'm curious. . . . was your engine builder primarily a CAR engine builder?

    Marine engines are different with respect to torque/hp/rpms. I'm asking because if your rpm numbers are correct, and you can only spin a Solas 21 to 4400, but you can spin a Solas 19 to 5700, it sounds like the engine has to really get spinning to develop it's horsepower, and at 4400 rpms it is still down on power big time. Works for a car, not so much for a boat.

    I have a Donzi Ski-Sporter 16, Volvo A290 with trim, a 1.61:1 ratio, and a 350 Chevy. I can spin a Solas 21 to just about 4700, and I can spin a Solas 19 to around 5000. That is more what I would expect from a marine engine. They have a pretty flat torque curve, and don't have to rev to almost 6000 to develop peak hp.

    Generally, each inch of pitch change will change rpms between 100 - 200. On my boat changing 2" of pitch (19" => 21") changed my rpms by 300.
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    Is this morphing back into a question of 'will a 290DP unit bolt onto an existing 270 transom ?'

    Because I've seen these questions a dozen times before here and I cannot recall anyone saying definitively 'yes' or I tried it ..no .

    It's been a while since I've seen a 290 up close , but from what I recall it looks a lot different than any similarities an Alpha might have with a Bravo , and we know that's not a direct changeover.

    Elsewhere , I've posted on my great results when I switched my single prop SX/A unit for a DPS/A on the same boat .
    Literally took an undriveable monster and turned it into a dream . And maybe even faster !
    Just because something's old doesn't mean you throw it away !

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