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  1. #1
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    Default I NEED SPEED!!! Prop question.

    I have a 72 Glassmaster with the 2.3 140hp. I took it on the lake today for the first time with my parents and their 3.0 135hp WAXED me on the water.

    My prop is pretty messed up now. Looks like someone didn't care what they were running over

    I know it's time for a new prop but have no idea what to get!! I see all these numbers with diameter and pitch and I have no friggin clue what any of this means or what setup would be best for me! I know I have three blades right now and they're screwed up.. that's it.

    Can someone help me find a good setup so I can at least keep up with my folks!?

    Your help is appreciated!

  2. #2
    Commander Triton II's Avatar
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    Default Re: I NEED SPEED!!! Prop question.

    C-P, some more info will help us to help you. What's the length and weight of your boat and the exact engine type. Also, when you say you "see all these numbers" can you tell us what they are if they're stamped on the prop hub, or do you mean you've seen "all these numbers" in various posts on this site?

    If the numbers are on the prop somewhere, I'd start by going to a prop shop with the prop and see if they can repair the blades. If not the next step would be to borrow a prop with the same numbers. Generally they'll be something like 14 x 19 K which means the prop is 14 inches in diameter with a pitch of 19 inches - the K being the identifier for the shaft fitment. Let us know what your numbers etc are and it will help.

    If the shop will lend you a prop to test it then see if the boat will achieve the lower end of its ideal WOT rpm range when heavily loaded and the top of its WOT rpm range when lightly loaded - if so the prop is about right. If the motor revs too high at WOT, then you need to go up in pitch, if too low you need to go down.

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  3. #3
    Moderator Bondo's Avatar
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    Default Re: I NEED SPEED!!! Prop question.

    I have a 72 Glassmaster with the 2.3 140hp.
    Ayuh,... Tell Us what ya Really got,....

    Merc never Ever used a 2.3l motor...
    Any Grease is Better,..... Than No Grease at All.......

  4. #4
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    Default Re: I NEED SPEED!!! Prop question.

    We'll be glad to help.
    Please read the stickies at the top of the page and get us as much info as possible.
    Prop size may be near the base of the blades or under the prop nut.

  5. #5

    Default Re: I NEED SPEED!!! Prop question.

    according to me triton is right

  6. #6
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    Default Re: I NEED SPEED!!! Prop question.

    Quote Originally Posted by ashusood View Post
    according to me triton is right
    Yes,and it is important we establish if the setup is working right.Sometimes a motor has problems,or the tach is wrong or the boat has problems.Without the priliminary numbers there is no way to know which way to go.

  7. #7
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    Default Re: I NEED SPEED!!! Prop question.

    Quote Originally Posted by Bond-o View Post
    Ayuh,... Tell Us what ya Really got,....

    Merc never Ever used a 2.3l motor...
    The previous owner told me Ford 2.3, I'm guessing maybe it's really a 3.0

    @Triton - If I would've found those numbers stamped on the prop I wouldn't have posted in here. By "all these numbers" I mean all the different diameter x pitch setups. I'm pretty sure that a shop WILL NOT let me test out different props like you suggest. I guess I'll just ask someone at the marina shop, maybe they can help.

    To clarify, the boat is a '72 Glassmaster 8 passenger 18ft with a Mercruiser 140 hp I/O

  8. #8
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    Default Re: I NEED SPEED!!! Prop question.

    Quote Originally Posted by steelespike View Post
    Yes,and it is important we establish if the setup is working right.Sometimes a motor has problems,or the tach is wrong or the boat has problems.Without the priliminary numbers there is no way to know which way to go.
    The tach doesn't work :/ The speedo read 32 mph WOT with 4 150ish lb adults.. The prop, to me, looks like the same prop on my other two boats size wise. I can find the diameter with a tape measure if that helps.

  9. #9
    Petty Officer 1st Class not enuf toys's Avatar
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    Default Re: I NEED SPEED!!! Prop question.

    unfortunately your not giving us too much to go off of. makes it hard to just say "x" will work.

    we must have tach info to know how the boat is running. this will let us know less or more pitch then what you have currently....what do you have currently is also a must. look on the hub. usually stamped there.

    we really want to help but your not giving us anything
    If you dont know how to fix it the RIGHT way dont!!

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  10. #10
    Commander 45Auto's Avatar
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    Default Re: I NEED SPEED!!! Prop question.

    Don't be surprised if mid 30's is all it will ever do no matter how much money you throw at it .....
    Any opinions expressed above are worth exactly what you paid for them!

  11. #11
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    Default Re: I NEED SPEED!!! Prop question.

    ChevyPower, the following information is absolutely mandatory in order for anyone to offer any type of recommendation to you:

    1. EXACT peak RPM operating range of your engine...I assume you don't know this since you're not even sure what size your motor is. So if you provide us with exact and complete serial numbers from your engine and outdrive, someone here can probably decode it.
    2. The pitch dimension of your current prop. This will be stamped somewhere on almost all props. You will often need to remove the prop to find the numbers. Whatever numbers you find, share them.
    3. Your current RPMS when running at your top speed. (yes, this means you MUST have a functional tach hooked up)

    If you cannot provide 1, 2, and 3 above, then you really have no option but to try locally at a local marina or prop shop. They can slap a random known prop on the boat, test drive-it (again, absolutely mandatory to do this with a functioning tach), see how it performs, and try another to move your RPMS in whatever direction you need to go.

    I also strongly suggest, before you do any of this, that the boat be given an extremely comprehensive tune-up....points, plugs, wires, cap, rotor, adjust/set timing and carb, compression check, throttle cable adjustment etc etc etc. Buying a prop that is designed for a poorly tuned motor would be a waste of money.

    Correct propping is 100% based on engine RPM. So without a tach you are 100% dead in the water...

  12. #12
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    Default Re: I NEED SPEED!!! Prop question.

    Got the tach working today.. 5,000 rpm WOT. The prop is original from 1972 and the serial number is no longer legible.

    Tune up was recently done by PO.. supposedly. But the engine runs like it should. If I had tune-up issues I'm sure I would be able to tell regardless of what prop I'm running.

    I'm giving you guys all I can. I also contacted the marina shop. They weren't cool with letting me test drive different props til I found the one I wanted.. figured as much.

  13. #13
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    Default Re: I NEED SPEED!!! Prop question.

    Its very possible that a prop is not your solution.
    The motor may have a problem,Perhaps as simple as the throttle isn't opening all the way.
    Motor could have issues like bad valves,bad rings,timed wrong,running on 3 cylinders.
    Boat could have problems,a hook in the bottom or it could have absorbed water in the hull or the flotation foam under the floor.The only way to tell whats up is a test run lightly loaded
    Assuming everything is right a 18 footer should run about 40 mph and have a decent hole shot.When trimming up the boat should respond.Basically we have no info.
    Perhaps your parents prop will fit your boat; get the tach fixed and make some test runs.
    Having you read the stickies is so you know what we need in order to help you.
    Its not like training 101 or something. If you just want to stab in the dark
    On a healthy boat and motor a 17" prop should get you a good hole shot for water sports
    but you may have to watch the max rpm ,oops what am I saying. A 19 should give good all around performance with slower hole shot. Less likely to over rev. but could lug.
    If your likely to carry 8 often then the 17 is probably the better choice.

  14. #14
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    Default Re: I NEED SPEED!!! Prop question.

    Did you even read my last post?

    THE MOTOR IS IN GOOD CONDITION! Sure a NEW 18 foot 3.0 should run about 40 mph, this boat and motor is 39 years old! The boat has a decent hole shot and planes like it should. I do not have bad valves or rings and I'd know if it were running on 3 cylinders. I do the maintenance on ALL of my vehicles, as a matter of fact, I just replaced the timing belt and water pump in my Ranger and set the timing afterwards. If I had problems with my motor I would be in a different forum posting a different thread.

    I just took the boat out today, like I just stated, the tach read 5k at WOT and after adjusting trim I got up to around 34 mph. If you would've READ my post the current prop is, for lack of better words, SCREWED UP! It looks like someone put the prop on some pavement then turned the engine on, I doubt this is what actually happened.

    I gave you guys ALL the info asked for with the exception of the prop's s/n.. so BASICALLY you have most of the info.

    Any HELP would be greatly appreciated. Thanks!

  15. #15
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    Default Re: I NEED SPEED!!! Prop question.

    Rebuild the prop and Go Forward.
    And you have No Pics?? of the prop?
    SO What engine do you have?

  16. #16
    Moderator Bob_VT's Avatar
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    Default Re: I NEED SPEED!!! Prop question.

    Did you know that the HP ratings are very different and your 2.3 motor will never have a chance to pounce a new 3.0......... never. You just have to be happy with what you have or get a boat with a larger motor and a real modern outdrive. LOL I hope you never encounter the smallest Bayliner 175 with the 3.0 ......... you will never recover.
    This is a great link to boat specifications http://boatspecs.iboats.com/
    Please, shop iboats first!!


  17. #17
    Cadet Fish Foot's Avatar
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    Default Re: I NEED SPEED!!! Prop question.

    Take the prop off and take it to a repair shop. They will be able to tell you the specs on it and maybe evan repair it for cheeper than a new one.

  18. #18
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    Default Re: I NEED SPEED!!! Prop question.

    5,000 rpm is helpful information. But that's only one of the 3 things I asked for. We're still missing your motor's proper operating range RPM, and what your current prop is. Without that info, again nobody here can help you.

    This is why you are spinning your wheels on the internet and getting frustrated. We're 17 posts in, and we still have only 50% of the information needed to even try to guestimate a prop for you.

    It sounds to me like you are probably over-revving, likely due to the chewed up/damaged prop. I do not believe most of those old motors were set up to rev that fast. But if we don't know what prop you currently have, and what RPM you are supposed to be spinning, we can't suggest any props for you to change to.

    As has been stated, it seems only a local prop shop can help identify your prop for you, and make an educated recommendation based on your current RPM.

  19. #19
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    Default Re: I NEED SPEED!!! Prop question.

    Please keep in mind it takes me forever to write my posts and Im sure your latest post was up as I was writing.I'm guessing about 3 hours today with various interuptions. And why would a 39 year old 140 hp boat with a sound properly tuned motor run much slower the a newer boat. There are plenty of older boats posts that run in the high 30s and low 40s Suggesting your motor or boat may have prolems isn't a jab at you or your motor its just fact as these boats age.
    You would be surprised what they can do for a prop. However if the prop is original repair may not be worth the investment. Your rpm and speed are both suspect due to the prop
    condition.A prop shop still should be able to measure so you can have a size to start from.
    By the way my info suggests the 2.3 and 3.0 use the same ratio. so hopefully you can manipulate the prop size to get the best performance. But I guess a 2.3 up against a 3.0
    will struggle.You might have to slip a couple of bags of sand into your dads boat.
    Both the old 2.3 and 3.0 have a slightly lower max rpm 4600 compared to 4800 for say a 2000 3.0.

  20. #20
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    Default Re: I NEED SPEED!!! Prop question.

    2.3 keeps being brought up. We still have no accurate idea what engine he's even trying to prop here...LOL

    ChevyPower says he has a Mercruiser 140.
    He has also said he has a 2.3 Ford.

    These 2 statements are entirely contradictory, and they have contributed to great confusion.

    If it is true that he has a Mercruiser 140, he simply does not have a 2.3. As Bondo pointed out early in this thread, Mercruiser Ford 2.3 simply does not exist. Mercruiser DID, however, use a 2.5, generally rated at 120 HP. And OMC used a 2.3L Ford. The old Mercruiser 140 was a 3.0 General Motors mill.

  21. #21
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    Default Re: I NEED SPEED!!! Prop question.

    Quote Originally Posted by ChevyPower View Post
    The previous owner told me Ford 2.3, I'm guessing maybe it's really a 3.0
    I honestly don't know why 2.3 keeps being brought up. ^^ This was literally my second post. ^^
    The reason newer engines would run faster than older ones is because of innovations in engineering over the years. Compare a 1972 Corvette with the same size engine as a 2000 Corvette and tell me which one runs faster.
    I'll deal with this problem on my own terms. Thanks for the help anyways.

  22. #22
    Moderator Bob_VT's Avatar
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    Default Re: I NEED SPEED!!! Prop question.

    Quote Originally Posted by ChevyPower;3333081[B
    ]I have a 72 Glassmaster with the 2.3 140hp.[/B] I took it on the lake today for the first time with my parents and their 3.0 135hp WAXED me on the water.

    My prop is pretty messed up now. Looks like someone didn't care what they were running over

    I know it's time for a new prop but have no idea what to get!! I see all these numbers with diameter and pitch and I have no friggin clue what any of this means or what setup would be best for me! I know I have three blades right now and they're screwed up.. that's it.

    Can someone help me find a good setup so I can at least keep up with my folks!?

    Your help is appreciated!
    Quote Originally Posted by ChevyPower View Post
    I honestly don't know why 2.3 keeps being brought up. ^^ This was literally my second post. ^^
    The reason newer engines would run faster than older ones is because of innovations in engineering over the years. Compare a 1972 Corvette with the same size engine as a 2000 Corvette and tell me which one runs faster.
    I'll deal with this problem on my own terms. Thanks for the help anyways.
    You brought it up first! and here too http://forums.iboats.com/showthread....14#post3333014
    This is a great link to boat specifications http://boatspecs.iboats.com/
    Please, shop iboats first!!


  23. #23
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    Default Re: I NEED SPEED!!! Prop question.

    This is all completely redundant and absolutely off topic. I was obviously misinformed and mistaken. If you would read BOTH the post I made AND the other thread I created, you will realize I wrote that BEFORE I found out what type of engine my boat actually has!!

    So if you're done stating the obvious, we can all move forward in a productive manner. Craze1cars, now you see why the internet can be so frustrating. I keep spinning wheels and they keep throwing water on the pavement.

    I'll just do what I should've done in the first place.. Remove the prop and take it to a professional to get some REAL advice.

    Thanks for nothing iboaters :/

  24. #24
    Commander Triton II's Avatar
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    Default Re: I NEED SPEED!!! Prop question.

    C-P, I don't understand your last comment at all. In post #2 of this thread (i.e the FIRST reply to your request for help) you were advised (by me who lives 12,000 miles away and at least 15 hours ahead of you in time) to take the prop to a prop shop. That's what iboats can do for you - offer free advice 24/7. Despite your lack of gratitude as witnessed throughout this thread, but especially in the post immediately above, I for one hope you get your problem sorted and enjoy your boating.

    TII
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  25. #25
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    Default Re: I NEED SPEED!!! Prop question.

    Quote Originally Posted by ChevyPower View Post
    So if you're done stating the obvious, we can all move forward in a productive manner.
    I find this and several of other comments very rude and insulting to the people who are trying to help you solve your problem! Step back a bit, provide the information they request and let them help.

    Your 72 140HP (3.0L) will never equal a modern 135 HP 3.0L Mercruiser/Volvo. The old 140HP was rated at the crank where the new 135HP is rated at the prop, if the old 140Hp were rated at the prop it would be about 120-125HP.

    5000RPM is way too high for that old engine, you should be turning between 4200-4600RPM WOT. (Even the modern 3.0L should only turn 4800RPM WOT) If your tach is accurate, you need a higher pitched prop.

    With an old 18' glass boat and a 140HP engine I wouldn't expect more than low-mid 30's. Not only is the modern 3.0L engine more powerful, your parents boat is probably a faster hull too.

    I agree with SS for a "shot in the dark" recommendation, 17P for hole shot and watersports, 19P for top end speed with slower hole shot.

    BTW, I'm running a 72' 140HP Mercruiser in my 18' boat and use a 19P prop, this gets 33-34mph on the dash speedo with the engine turning 4300-4400 RPM WOT. Your results will probably be different.
    2001 Crestliner SuperHawk 1800, Mercruiser 140HP
    2007 Tracker 1436 jon boat, 7.5HP Force

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