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Contessa cb prop

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  • Centerline2
    commented on 's reply
    on my old 26 with the AQ170 I set the outdrive so the anti-cav plate was parallel with the bottom of the hull, then used the 24" tabs to adjust the trim attitude of the boat. it worked well and was a heavy boat as I had it set up for dive chartering... I had an elephant ear prop and pitched to allow about 250rpm above recommended for that engine... I could get 28mph with 6 adults and 5 sets of cold water dive gear on board. I know it was a bit overloaded but it rode as gentle as a cadillac in rough water.

  • kwb
    replied
    You were getting really good performance with the setup you had for a single prop.

    Use the tabs to lift the rear of boat a bit. I think the pin needed to be in the middle hole. Move batteries as far forward as possible. Store your beverages as far forward as possible. Don't put a 80quart cooler full of beer and Ice on the back deck.

    I had same boat with the DP drive and I could cruise at about 3200 rpm and 20kn when we were out for a weekend.... loaded up for a week, not so much, had to add a few hundred R's. Hard to spend that kind of money on a boat of that age but if you are attached to it .... it is a worthwhile endeavor. You will want B2 or B3 props.

    Leave a comment:


  • Centerline2
    replied
    Originally posted by Andrew fraser View Post
    It was showing 20 knotts on the garmin gps but stern was very very deep and front end still very high.

    I had a different make boat and bin out with a few friends boats and you cant feel when they lift and plane. MIne didnt feel like it wanted to lift. It just wanted to “dig in”

    . The leg is on the second hole from transom (theres 4 i think) and was wondering if the leg is too far out hence its pushing the stern down and thats why she “digs in” instead of planing. So was wondering if moving to 1st hole might solve that. What you guys think
    if you were showing 20kts, you were either on plane or you have the the trim of the boat seriously out of adjustment...
    yes, if the outdrive is trimmed out/up too far, it will cause the bow to rise and the stern to be driven deeper... also, if you have an extreme amount of weight in the stern without any up front, it can cause the stern to be so heavy that it cant be lifted enough with the power you have available from the engine...
    and if you have the tabs fully down to get the stern to lift, and the outdrive trimmed too high (pushing the stern down), they are fighting one another and the speed and economy will suffer greatly... and the 28 will never pop up on plane like an 18ft runabout, without a substantial amount more power pushing it, but should make a smooth gentle transition from plowing to planing... if you dont have trim tabs, you need to install some if you want to get the best performance from the outdrive you have...

    Leave a comment:


  • 2850Bounty
    replied
    Here is an old video showing two identical boats.... one with the VP s/p drive and one with the VP DP drive.


    https://www.youtube.com/watch?v=MBd0mtMHT6w

    The DP was introduced in 1983 .
    Volvo Penta still holds the patent rights for their unique propeller design.

    For those who want to install a DP on an existing VP s/p system, only the lower gear unit needs to be changed out.

    Leave a comment:


  • nwboater62
    replied
    Like Rick said! $$$ but well worth it! I have a DP behind a 5.7 in my Contessa and it performs nicely. She gets right out of the hole and cruises comfortably around 22 MPH at 3400RPM.

    Leave a comment:


  • 2850Bounty
    replied
    Install a 1.95:1 Duo Prop and your problem will disappear.

    Leave a comment:


  • Andrew fraser
    replied
    Hi all

    sorry i bin away from forum for along time but im back that what counts right lol.

    It was showing 20 knotts on the garmin gps but stern was very very deep and front end still very high. I had a different make boat and bin out of a few friends boats. And you cant feel when they lift and plane. MIne didnt feel like it wanted to lift. It just wanted to “dig in” . The leg is on the secound hole from transom (theres 4 i think) and was wondering if the leg is too far out hence its pushing the stern down and thats why she “digs in” instead of planing. So was wondering if moving to 1st hole might solve that. What you guys think

    Leave a comment:


  • SKUA_28_Contessa
    replied
    16 x16 or 15 elephant ear OEM or Michigan wheel oem replacement are the optimal prop with this combo, assuming your engine is good. It should do 25-28 mph with this combo. Larger tabs in the 18-24 inch drop tab configuration and wedge the tabs so the line up with the warter flow, and you can do 32-35 WOT at 44-4600 rpm.

    If you were doing 20 knots you were on plane. This boat will plane out at 16 or so.

    Leave a comment:


  • Nauti_Mike
    commented on 's reply
    Agree.

  • Centerline2
    replied
    Originally posted by Andrew fraser View Post
    Hey all

    i had it out again and it did mid teens. Not sure how much tidal flow there was. I think 3 ish knotts. Wot was 3800. I contacted the prop place they said its the smallest pitch they sell/ make but they could reprofile the prop a pitch or two lower. Is it worth it? Does it work? And downsides like weaker prop etc? Or do i go back to a alumimum prop and lower pitch ?
    its a lot cheaper to have the prop profiled than it is to buy a new one again.... 3800rpm is not nearly enough, and it may take 2-3 inches of pitch change to get where you should be... the problem is, they problably cant make that much change in the prop..

    personally, I am a fan of the less expensive aluminum props for most applications on these type of boats... when one is looking for ultimate high speed performance, then stainless becomes a good option, but the 28 will need a much larger and more powerful engine before one will see a difference in performance in stainless over a properly sized aluminum prop....

    Leave a comment:


  • Andrew fraser
    replied
    Hey all

    i had it out again and it did mid teens. Not sure how much tidal flow there was. I think 3 ish knotts. Wot was 3800. I contacted the prop place they said its the smallest pitch they sell/ make but they could reprofile the prop a pitch or two lower. Is it worth it? Does it work? And downsides like weaker prop etc? Or do i go back to a alumimum prop and lower pitch ?

    Leave a comment:


  • Nauti_Mike
    replied
    Originally posted by Andrew fraser View Post
    Hey all

    i have a 86 contessa 5.7. I have alot of weight on back end (battery’s ). I had a aluminium 16(dia) x 15 pitch 3 blade. she would due about 20 knotts at 4300 -4400 rpm but wouldnt get her stern out to plane. I was advised if i went to a 4 blade and stainless i would get a bit more “punch” and it probably make her plane but might lose a few knotts top end. I got ahold of a brand new solas saturn 4 blade 15.5(dia) x 15 pitch. I only tried it once so far and all she do was 8.4 knotts dont know about rpm. I will check when i try again tomorrow. What i cant understand is why the stainless 4 blade is so much slower at the same pitch. Any ideas.. of
    The SS prop has more drag from the extra blade and is heavier than the aluminum so the pitch should have been reduced, since you stayed the same pitch your performance will decrease as you experienced.

    Leave a comment:


  • Centerline2
    replied
    Originally posted by Andrew fraser View Post
    The 16x15 was rh and the 15.5x15 is left hand ( or other way around) but bin told from many many people the 280 can run eather way. Unless anyone here knows better ???
    the 270/280 can be ran either way. one only has to pull the cover off the drive and switch the linkage rod to the other end of the shift lever so the helm control throw is in the correct direction.

    a 4 blade prop grabs more water..... a number of things here. you either need more slip, which is partially controlled by diameter and partially controlled by the individual blade surface area (and number of blades), or less pitch... a fat bladed prop has less slip, and a skinny bladed one has a lot of slip, but this depends on how much power is applied to it.
    the design of a prop is a very dynamic thing and any slight change in design or applied power will change its characteristics across the board...

    its been said by many that a fat bladed prop with the correct pitch is better than a standard size prop. and in my experience, a 4 bladed prop is an expense that is only reasonable when one has excess power that needs to be used.... the contessa with a 5.7 doesnt qualify as a boat with excess power.

    the 5.7 engine should run at its recommended 4600rpm, and on a heavy boat, maybe a few extra rpm wouldnt hurt... BUT, not to be ran there all the time, but just be able to make the rpm so when at cruise rpm range, the engine is running without laboring on the torque curve......

    personally, I firmly believe the trim tabs installed are too small for the boat, I installed the larger 12x24 tabs on mine and it made a huge difference... the OEM sized tabs need to be used in conjunction with the trim of the outdrive to get the attitude of the boat correct, and too much or too little of one or the other will cause the engine to labor, not climb fully on plane, and not make the rpm necessary to insure its running easily within its torque curve..

    Leave a comment:


  • Andrew fraser
    replied
    The 16x15 was rh and the 15.5x15 is left hand ( or other way around) but bin told from many many people the 280 can run eather way. Unless anyone here knows better ???

    Leave a comment:


  • drewhaas
    replied
    I don’t even know if it’s possible but the only thing that comes to mind is could the prop be mounted backwards?

    Leave a comment:

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