Minnesota Classic Glastron Forum

General Category => General Discussion => Topic started by: pyro225 on September 07, 2017, 11:35:21 AM

Title: Prop question
Post by: pyro225 on September 07, 2017, 11:35:21 AM
Ok this is a little bit naughty as this isn't for my glastron it's for my regal but hoping you will let it slide and help me ;-) - so it's an 18ft bowrider with a 120 mercruiser diesel.

It came with a 14.25x21p prop and the alpha 1.

Problem:
 
3ppl plus gear or 4ppl no gear get to speed and on the plane no problem although it is a slow process takes me about 30 seconds to get up .

Now if I'm doing a big trip with gear and 6 ppl she just shoves the bow in the air and goes about 12mph flat out.

I bought a vengeance prop 13.75 x21p and still the same problem but it makes just below planing speed flat out now 15mph.

I am not interested in losing a couple of mph top end I just want to be able to cruise on plane.. FYI mechanically she's sound....

I also bought a 19p laser II but think she will over rev...

So now after some serious research I'm thinking of trading all 3 props for a high five but wondered if anyone has any experience with these and if there's a chance it will cure me? Also pitch wise do I stick at 21 or drop?

Thanks!!!


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Title: Re: Prop question
Post by: Plugcheck on September 07, 2017, 11:47:25 AM
      Certainly I'm  no expert on props, but just to clarify, its a Mercruiser 120hp DIESEL engine?   I would suggest a prop with more stern lift.
Title: Re: Prop question
Post by: Diamond Chad on September 07, 2017, 12:22:33 PM
If it cannot push the boat up on to plane with the 21p at that weight, try the 19p.  That is not such a big step that over rev should be a problem.  If you were saying that you were going to try a 13p, then yes, maybe. 
Title: Re: Prop question
Post by: pyro225 on September 07, 2017, 12:25:42 PM
It's is indeed a strange combo - take a look at the comparison for reference http://www.popularmechanics.com/adventure/outdoors/a207/1277216/




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Title: Re: Prop question
Post by: pyro225 on September 07, 2017, 12:26:35 PM
Ok diamond chad - would the high five bring much more to the table? If so which pitch?


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Title: Re: Prop question
Post by: dorelse on September 07, 2017, 01:07:49 PM
Ok diamond chad - would the high five bring much more to the table? If so which pitch?


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None of us have Diesel's...so you're going to have to figure it out, or ask the European guys.
Title: Re: Prop question
Post by: pyro225 on September 07, 2017, 01:08:58 PM
fair point - as it has more torque and only a little less power than the 3.0 gas - if we were talking about that would it make any difference ?


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Title: Re: Prop question
Post by: Diamond Chad on September 07, 2017, 01:12:18 PM
I think a high 5 slips less, and drags more (uses more energy to turn).  I have heard that you drop a step (2 ") in pitch when you go to a 5 blade.  I do not have first hand knowledge.  But if your 21" 3 blade was not spinning out or losing grip while trying to push it onto plane at 12 mph with the nose up, the 19 probably will not either so grip is not the problem, its pitch.
Title: Re: Prop question
Post by: fireman24mn on September 07, 2017, 01:22:22 PM
I would try something in a 4 blade 20p.
Title: Re: Prop question
Post by: pyro225 on September 07, 2017, 04:23:10 PM
Ok maybe I will try the laser - do i need to cover the vent holes on these boats ?


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Title: Re: Prop question
Post by: Diamond Chad on September 07, 2017, 04:52:02 PM
Since you already own it, it won't cost you anything to try.  Vent holes help 2 stokes get needed rpm.  I think you plug them on an I/O.
Title: Re: Prop question
Post by: Hyperacme on September 08, 2017, 09:26:02 AM
Mercury PVS plugs ...
https://www.youtube.com/watch?v=UvYz9iyfyYE (https://www.youtube.com/watch?v=UvYz9iyfyYE)

You can play with this ...
https://www.mercurymarine.com/en/us/propellers/selector/#/step-one (https://www.mercurymarine.com/en/us/propellers/selector/#/step-one)

There are so many variable with your boat / motor / weight / loads / weather / water conditions / etc. that the only way to know is testing some props. Even if you find one that works well for a light load, you might need another for heavy loads.
I have a Laser II 22P for speed and keep a spare Aluminum 19P to pull a tube / skier.

" I also bought a 19p laser II but think she will over rev... "

Try it ! 
You'll never know until you do.


 
Title: Re: Prop question
Post by: pyro225 on September 11, 2017, 01:58:25 PM
Ha thanks guys - sorry I know it sounds like I like the sound of my own voice on this but my local dealer rang (I left my number a while ago) and said he has brand new 4 blade alu props clearance event for £50 - if I were to try one they have a 20 or 18 pitch which would be safer to buy if mine was 21 stock? The diameter is slightly less than stock sat well stock 14.25 these are 13.75


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Title: Re: Prop question
Post by: Plugcheck on September 11, 2017, 02:04:42 PM
    New aluminum props for 50 quid?   I'd jump on that, smaller diameter than your 21p, I'd give the 19 a go.   Easy to get your money back at that price if it doesn't work out.
Title: Re: Prop question
Post by: pyro225 on September 11, 2017, 02:06:14 PM
Yep brand new but they are even sizes (which is odd ) maybe why they are cheap only have 20p or 18p which is either side of ideal what do you reckon would be best overall? 18 for less strain and easier plane?


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Title: Re: Prop question
Post by: Plugcheck on September 11, 2017, 02:23:52 PM
      Well, I'm not an expert, but most every boat has a target WOT(Wide open Throttle) RPM range printed on it, or it can be found somewhere in literature on the product.  Just a guess, maybe 3000 RPM for that Diesel?   Propping down in diameter without changing pitch will change the engine RPM's, how far are they off.   If only a few hundred then the 20 would be a good start, but if 600 rpms or more then I'd opt for the 18.     Someone correct me, but I seem to remember about 200-300 rpms per inch of pitch?  Considering the diameter remains the same.
Title: Re: Prop question
Post by: pyro225 on September 11, 2017, 03:10:21 PM
Not to sound like a massive loser but it's a performance turbo diesel :-) 120bhp 1.7 and 4400-4600rpm not far from the 3.0 loaded it's about 500 rpm off unloaded it hits full chat within 30 seconds of wot


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Title: Re: Prop question
Post by: Plugcheck on September 11, 2017, 03:30:04 PM
    Specs call for a 14.5 diameter in 19 pitch.   Try the 13.75 in a 20p, hard to go wrong for the price.     I still would try the Laser first with the PVS holes covered first and get an idea where your RPM's are.
Title: Re: Prop question
Post by: pyro225 on September 12, 2017, 08:01:56 AM
Hmm I rang back and I think I misunderstood its one of these not alu - any experience? http://comprop.com


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Title: Re: Prop question
Post by: dorelse on September 12, 2017, 09:39:58 AM
Hmm I rang back and I think I misunderstood its one of these not alu - any experience? http://comprop.com (http://comprop.com)


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Yep, that's a composite (Plastic) prop.  I have a couple Piranha props, also composite, and a Gil Six Gun prop as well.

I like the Piranha because they help protect the outdrive by their ability to flex and absorb any hits, while breaking more easily if I hit something serious.  Blades are $19 each to replace and slide into the hub.  I have a 4 blade & 3 blade hub, and run a 23p 3 blade, or a 21p 4 blade.

My Gil Six Gun has 6 smaller blades and I run a 21p on it as well.  I think that prop was $79 and also has individually replaceable blades, though they're out of business now, so blades are hard to find.  My Metric likes this prop a lot more than my CVZ did.

Comprops are essentially molded props that, like it says, are temporary spares to get you home.  I've used the Piranha as my primary prop for years now and have been really happy.  I think I lose about 1-2 mph on the top end over a SS but am on par with a Aluminum prop.

I like them b/c I don't have a lot money in props...and if they break...$19...no big deal.
Title: Re: Prop question
Post by: pyro225 on September 12, 2017, 06:32:54 PM
So you are saying I shouldn't get this as a main prop? On their website it says they were designed as a spare but now they are a lot better and new boats come with the like regals crown lines etc


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Title: Re: Prop question
Post by: dorelse on September 12, 2017, 11:54:44 PM
I have never seen another composite prop in the wild besides mine.  It also says that the manufacturer offers a Quicksilver 19P Aluminium blade as well.  I would guess that 95%+ are sold with the AL prop on them.  Not sure about Europe.
Title: Re: Prop question
Post by: pyro225 on September 18, 2017, 12:14:10 PM
Back... just bought it... probably should have asked on here or the shop prior to purchase but it’s just dawned on me... i normally put a block of wood between the cav plate and the prop to tighten the prop... will these fins break off on the comp one if I do the same?


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Title: Re: Prop question
Post by: pyro225 on September 20, 2017, 01:45:07 PM
wow what a difference much smoother and more balanced gets on the plane in 5 seconds now... just need to try her loaded up!


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Title: Re: Prop question
Post by: pyro225 on October 28, 2017, 01:17:21 PM
 Rising this from the dead - took her out for the penultimate trip of the season- cruising at 30mph hits some reeds - and got a dirty vibration stopped her and guess what..? Missing blade! Two trips grrr POS - lucky I was only two miles from home so cruised back at a massive 2mph!


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Title: Re: Prop question
Post by: Hyperacme on October 28, 2017, 02:58:34 PM
Most carry a spare prop with them, like a spare tire in your boot ..
You should carry some spare blades and wrench to repair ... In case it ever happens again.
Or just a cheap banged up spare aluminum prop to get you home.
Title: Re: Prop question
Post by: pyro225 on October 28, 2017, 06:01:12 PM
Yea good thinking - would it do any damage to the drive as out of balance? If I had an ally prop would it have ripped the reeds to you think? Now I need a new 4 blade


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