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  1. #1

    Default Starcraft Islander 191 3.0 Merc prop selection ?

    I have justout bought an aluminum 1998 Starcraft Islander 191v, it has a 3.0 mercruiser 135hp and an alpha 1 leg.

    Boat is 2200 lb plus 100-180 lb gas, 650 lb people and gear it ran 34 mph WOT at 4400rpm. It is hard to read the numbers on the prop, it is fairly old looking, it has had the tips rebuilt but one of the blades the rebuilt part has been partly knocked off ( about 3/8"D x 1 1/4"L missing). I think that the last numbers are a ?? x 2? so assume it is a 21" pitch. boat cruises at 24-25 mph at 3400-3600rpm.

    This is a deep v hull, The above total weight of 3000 goes up to 3500 lb sometimes.

    I would not want to sacrifice cruise speed but if I could get better acceleration etc that would be good.
    Use it for cruising with family, fishing, tubing and a bit of waterskiing. Was thinking of having the existing prop rebuilt/repaired as a spare and getting a new prop.

    does anyone know what this boat had as an original prop? Was thinking of going down? to 19 or 20 pitch and getting the wot rpm up a bit, would like to stick with an affordable easy to install prop. What about 14.5" x 19 ? Also make of prop that would fit original hub would be good.

    ...and then I need to fix the super stiff steering, maybe with hydraulic conversion?, but I guess that is for another time and forum.

    Thanks for your help and time...

  2. #2

    Default Re: Starcraft Islander 191 3.0 Merc prop selection ?

    Oh by the way the speeds were with a gps. also I asked a mercruiser dealer over the phone what to go for and he suggested either 14"x 19 or or 14.5"x19 pitch. Would the 14.5"x19pitch goa faster than the 14x19?

    thanks for your expertise guys

  3. #3
    Petty Officer 2nd Class rs1lollie's Avatar
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    Default Re: Starcraft Islander 191 3.0 Merc prop selection ?

    I would look into a 4 blade prop in the 14x19 or 14x20 it gives better hole shot and planes a lot faster at lower speeds, and less vibration at wot speed.

  4. #4
    Commander hwsiii's Avatar
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    Default Re: Starcraft Islander 191 3.0 Merc prop selection ?

    Wonder, you are showing a 22% prop slip at WOT and it is definitely worse at ruising speeds, and a 3,000 pound allup weight right now if your gear ratio is 2:1, please verify this. With a weight of 3,500 pounds it is just going to get worse, you need to purhase a Solas Amita 4 blade prop with a 19" pith as this will derease your prop slip and raise your RPM slightly and inrease your hole shot with a commensurate increase in RPM throughout your whole RPM band. And it should cost you less than $ 125.


    Prop Slip




    Please come back and give me your new WOT RPM and speed for my database.



    H

  5. #5

    Default Re: Starcraft Islander 191 3.0 Merc prop selection ?

    Wow, thanks for the quick response guys. I will double check my speed / rpm later this week and get back to you before i order a new prop. I was in an inlet and there may have been some tidal effect. will do a run up and a run back to average it out.

    About what sort of 3500 rpm cruise speed and wot speed and rpm do you think I could get with a Solas Amita 4, 4-Blade Aluminum Prop, Fits Mercury/Mariner/Mercruiser/Honda 135-300 HP, 14.25 x 19-P RH .

    And what if I went to a 20 pitch, not sure if solas amita has a 20 pitch, but how much would that change cruise speed? I know I am asking you alot with less than perfect info :-/

    Won't be doing much water skiing of 200 lb people, just a couple times a year.

    cheers

  6. #6

    Default Re: Starcraft Islander 191 3.0 Merc prop selection ?

    Drive is 1998 Alpha Generation 2 with a 2.00 to 1 ratio as you thought

  7. #7
    Commander hwsiii's Avatar
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    Default Re: Starcraft Islander 191 3.0 Merc prop selection ?

    Assoon as you get me some good numbers I an tell you. But get me speed and RPM for 3,000, 3,500, 4000 and WOT RPM.


    H

  8. #8

    Default Re: Starcraft Islander 191 3.0 Merc prop selection ?

    Hello hwsiii
    I went out in the ocean with boat 2200, gas 170, people 460, kicker 130, gear 90 total 3100 lb. we were in about 8-12" sea which slowed us a bit.

    3000 rpm 17.8mph - variable, barely keeps on plane
    3500 rpm 24.5mph
    4000 rpm 30 mph
    4350 rpm 33.7 mph WOT

    and as I mentionsed the tip of one blade is missing about 3/8" by 2", I think it is a 21' pitch, numbers are hard to read, not sure of diameter.

    thanks again for your expertise.

  9. #9

    Default Re: Starcraft Islander 191 3.0 Merc prop selection ?

    more info for you,

    I have a happy troller mounted on the cavitation plate, it is used to slow the boat down when trolling, when not used it folds up and acts a little like a hydrofoil I believe, probably slows the boat a bit?

    Deadrise (deg at transom) 18

    max recomended manufacturer rpm 4400-4800

    boat is aluminium with rivets on it including the bottom of the boat.

    hope this helps hwsiii

  10. #10
    Commander hwsiii's Avatar
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    Default Re: Starcraft Islander 191 3.0 Merc prop selection ?

    It does, and it verifies what we decided earlier, with a weight of 3,500 pounds it is just going to get worse, you need to purchase a Solas Amita 4 blade or Solas Rubex 4 blade prop with a 19" pitch as this will decrease your prop slip and raise your RPM slightly and increase your hole shot with a commensurate increase in RPM throughout your whole RPM band. And it should cost you less than $ 125.


    H

  11. #11

    Default Re: Starcraft Islander 191 3.0 Merc prop selection ?

    Thanks Hwsiii for your help. I got out yesterday and the sea was flat so tried out my new 19" pitch 4 blade solas amita.
    We had about 3000 lbs all up weight, and here are the new numbers...

    3000rpm 19.9mph, planes much better at this rpm
    3500rpm 26.5mph, cruise speed
    4000rpm 31.8mph
    4450rpm 35.5mph WOT

    Compares much better than the old figures with a damaged 21 pitch 3 blade, below with 3100 lbs weight
    3000 rpm 17.8mph - variable, barely keeps on plane
    3500 rpm 24.5mph
    4000 rpm 30 mph
    4350 rpm 33.7 mph WOT

    cheers

  12. #12
    Commander hwsiii's Avatar
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    Default Re: Starcraft Islander 191 3.0 Merc prop selection ?

    Here are the new numbers for your prop slip with the Solas 19" 4 blade. I am very glad you are happy.

    Your prop slip was cut in half.

    Prop Slip 2





    H

  13. #13

    Default Re: Starcraft Islander 191 3.0 Merc prop selection ?

    Just an update. We are still using the solas amita 19" and that really helped with getting up on plane also. The other great thing that transformed the performance of this boat was putting on Smart tabs. This boat went frro planing at 18mph to planing at 11-12mph and that make a huge difference when you are running in a big sea or chop. We can also now just use half throttle to get up on plane where before you would just have bumbled along with nose bow up and stern down. Fairly easy install we used ST1290-60 http://forums.iboats.com/boat-topics...er-133359.html
    and have them set fairly light. With a heavy kicker on the boat it was always listing over to the port side badly and by setting the pport side tab slightly firmer it has reducing the listing while underway. So for you guys with underperforming underpowerd boats the smart tabs I highly reccomend. Set them once and forget them. Much cheaper than trim tabs but if wind has you listing over now you have to adjust the load. The right prop and smart tabs really changed the ways this boat performs...hope this helps.

  14. #14
    Supreme Mariner
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    Default Re: Starcraft Islander 191 3.0 Merc prop selection ?

    Great info. What did the tabs do to top end? Haven't seen anything of hwsiii in a couple of years since the gulf oil spill.
    He really had the prop numbers down. Happy boating.

  15. #15

    Default Re: Starcraft Islander 191 3.0 Merc prop selection ?

    To set thaw smart tabs up once they are installed we pulled the pins out so the tabs are not working and did a couple runs to measure wot speed. Then in the shallows we put the pins in the middle holes and did another run. We lost about 2 mph at wot so we adjusted them lighter a couple of times. Finally on the lightest setting on starboard and second lightest setting on port we lost about 1/2mph. However the way the boat handled was vastly improved. We may have set the initial angle on the tabs a little to much. That is, perhaps we could have moved the actuators up a little higher on the transom so the tabs did not hang down as far. I suspect lighter actuaters would have worked well also. Set up properly you should be losing very little or no top speed.

    Great on the lake pulling tubes slow and zig zagging around as you don't need to worry about fiddling with electric trim tabs. Also great in a swell or chop as we can plane along slowly. Before it was 8mph or 20mph and nothing much in between. Hope this helps someone. Cheers

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