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Limshady88

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Posts: 81
Reply with quote  #16 
Quote:
Originally Posted by PhilH12
++ to Olypopper!  Just a thought that "many" analog tach's will read low (that might be why he asked [wink]).  Not saying yours are, but they may both be reading 200 - 300 low at WOT?

Best to use a tach that's reading from the EMM (via NMEA 2K or EV Diag), at least for your prop/rpm testing.

Phil


Yes, my analog gauge shows about 150 less RPM than my Garmin which is NMEA connected to the motors

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The Reel Limshady 
FlyingTexan

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Posts: 33
Reply with quote  #17 
Putting all the stuff about the gauges on the back burner for a second. Would I really see any difference going from a 21p to a 19p that’s a bigger prop RPM wise? I’d like about 500 more.
PhilH12

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Reply with quote  #18 
There's a whole host of variables here.  The "general" rule is about 200 rpm's per inch of pitch, but as you've noted, you've got a bigger blade, too.

My best guess is that you'll pick up at least 250 - 300 or so(?), and the rest may well be in your analog gauge readings to hit Optimum.

See if you can find Loaner/Test props that you can return if needed.  A good prop shop should be able to help, especially when you'll be getting two of them when you hit the sweet spot.  [wink]

Phil

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20' Weeres fishing pontoon
90 HP E-Tec E90DPLSUM  05184332
Lake Tawakoni, TX - Catfish Capital of Texas
steelhead

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Posts: 3,598
Reply with quote  #19 
Post up some clear high res video of lower units on plane above 4500 rpms so we can tell if antiventilation plate is above solid green water and not causing extra drag, loss of mpg and speed.  Height of AV plate in relationship to keel is ONLY a starting point on deep V hulls.
Waste of money propping expensive SS until motor height is correct.

Old motors, need to make sure they're at top performance, get the E. Diagnostics software and cable, best place Joe at the place that keeps this site on the air, Barnacle Bills top of page.  Post up an Engine Profile history report in .pdf format.  The software will give exact motor rpms needed for propping correctly.  2 strokes that are overpropped carbon badly and destroys engine life from lugging.  Overpropped 4 strokes "make oil" suffer from rich gas running into crankcase burning out bearings and taking out rings.
Those old 175 V6 small blocks don't even make max HP until they hit 5400 rpms.  Why give away HP and use extra fuel?

Have boat fuel system vacuum and air leak bubble tests been performed at above 4000 rpms on water under prop load?  Critical on old boat fuel system and old motors.  Motor not running up to max performance will result in wrong expensive props pitch.

That deep V light bow hull requires a stern lifter prop, where most of the weight is at, to reduce stern hydrodynamic drag and increase ride qualities, get the bow down just skimming the water.  Increases controllability and ride smoothness.
Lots of prop trailing edge cupping, NO tip cupping, little to no blade rake.

Get the injectors cleaned this winter off season at one of the injector cleaning service businesses listed in forum posts.  No use burning out a cylinder from 12 year old plugged dirty gummed up injectors

What Oly said, Rebels or my suggestion pair of the new RX3 stern lifter props.  Both are great on deep Vs offshore for handling, lots of stern lift, tops for mpg, 3 blade fast props.
Merc props are way overpriced for what one gets, they make few stern lifter props.  30% more than BRP Evinrude SS props.  Slow season now in US, lots of dealers are willing to make deals on parts.

FlyingTexan

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Posts: 33
Reply with quote  #20 
Quote:
Originally Posted by steelhead
Post up some clear high res video of lower units on plane above 4500 rpms so we can tell if antiventilation plate is above solid green water and not causing extra drag, loss of mpg and speed.  Height of AV plate in relationship to keel is ONLY a starting point on deep V hulls.
Waste of money propping expensive SS until motor height is correct.

Old motors, need to make sure they're at top performance, get the E. Diagnostics software and cable, best place Joe at the place that keeps this site on the air, Barnacle Bills top of page.  Post up an Engine Profile history report in .pdf format.  The software will give exact motor rpms needed for propping correctly.  2 strokes that are overpropped carbon badly and destroys engine life from lugging.  Overpropped 4 strokes "make oil" suffer from rich gas running into crankcase burning out bearings and taking out rings.
Those old 175 V6 small blocks don't even make max HP until they hit 5400 rpms.  Why give away HP and use extra fuel?

Have boat fuel system vacuum and air leak bubble tests been performed at above 4000 rpms on water under prop load?  Critical on old boat fuel system and old motors.  Motor not running up to max performance will result in wrong expensive props pitch.

That deep V light bow hull requires a stern lifter prop, where most of the weight is at, to reduce stern hydrodynamic drag and increase ride qualities, get the bow down just skimming the water.  Increases controllability and ride smoothness.
Lots of prop trailing edge cupping, NO tip cupping, little to no blade rake.

Get the injectors cleaned this winter off season at one of the injector cleaning service businesses listed in forum posts.  No use burning out a cylinder from 12 year old plugged dirty gummed up injectors

What Oly said, Rebels or my suggestion pair of the new RX3 stern lifter props.  Both are great on deep Vs offshore for handling, lots of stern lift, tops for mpg, 3 blade fast props.
Merc props are way overpriced for what one gets, they make few stern lifter props.  30% more than BRP Evinrude SS props.  Slow season now in US, lots of dealers are willing to make deals on parts.



Holy hell thats a post. Thank you! I did have my engines serviced, yesterday, where they checked compression and fire. I’ve already ordered my diagnostic cable/software so waiting on that to arrive. The engines are raised as high as they can go without some serious work. I think their height is right based on looking out the back when running. The motors came with, I bought it used, a hydrafoil on each one. I’ve seen real benefits from them in the past and figured they’d help this thing get on plane and be more effective with the trim. Am I right or should I pull them off? Sometimes we have several people and lots of cooler weight when booze cruising the river so figured they’d help me get on plane. What’s your thought on those?
steelhead

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Reply with quote  #21 
Some video would still help.  Especially at full max fishing load at plane speed and above.  Interested in seeing AV plate, spray off lower unit, prop rooster tail and spray off rear side/gunwales of boat

With strong stern lifter props like the BRPs mentioned or the PowerTech WBB4s, you won't need the mpg top speed stealing hydro-dynamically dragging wings of death.  HFs often cause chime walk on certain hull designs.  A cripple cheap solution to an easily fixed problem.  Nasty handling feel isn't it.
Take them off and test handling when you get the stern lifters on it.

Put trim tabs on, easy and much more control-ability of boat in different sea/wind conditions.
FlyingTexan

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Posts: 33
Reply with quote  #22 
Quote:
Originally Posted by steelhead
Some video would still help.  Especially at full max fishing load at plane speed and above.  Interested in seeing AV plate, spray off lower unit, prop rooster tail and spray off rear side/gunwales of boat

With strong stern lifter props like the BRPs mentioned or the PowerTech WBB4s, you won't need the mpg top speed stealing hydro-dynamically dragging wings of death.  HFs often cause chime walk on certain hull designs.  A cripple cheap solution to an easily fixed problem.  Nasty handling feel isn't it.
Take them off and test handling when you get the stern lifters on it.

Put trim tabs on, easy and much more control-ability of boat in different sea/wind conditions.
Excellent info. I’ll have to see when I can get it on the water next. It has tabs but inop at the moment so it’s on my list. The list is getting smaller though and I’ve actually enjoyed messing with it. Kind of “making her mine”. Really feel bad for the guy that had it rigged the way he did. Engines are running top notch however and I’ll get some data as soon as I can. Waiting on my cable to arrive in the mail before I drive back down.
FlyingTexan

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Posts: 33
Reply with quote  #23 
Well.... I’ve ordered a set of 19p Mirage plus props off eBay. I had forgotten I had ever made the offer and it was accepted today lol. But for $410 for the pair in pretty good condition I think I can make it work. Worst case I just put them back up for sale. Pretty soon I’ll be able to run my own prop shop! Hopefully I get my cable by Friday.


I do want to thank each of you for all the tips. I’ll be pulling the foils off, swapping these props on, plugging in the computer and going from there. It has really amazed me how many little tweaks there are. I also need to work on getting the trim tabs working but I know nothing about them so should be exciting.
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