Bravo I XS pro finish - Propman

[greenberet24]

Originally Posted by REW

Big Game,
I am curious as to why you have any interest at all in throwing a rooster tail behind your boat.

If you have water going up in the air, your prop is not pushing your boat ahead. i.e. you are losing push for any water that you are pushing up in the air.

Be safe
REW

I agree with you, REW. They say any spray over the height of your motor is a waste of gas.

Regards,
Gabe

[staylor]

If you find this prop- cherish it, protect it, and cover it with a prop blanket on the trailer so now one else can see it- because you've found the holy grail. On my SF 176 Starcraft w/150 Opti I run a 21 Tempest with added tip cup for rough water and best top end speed on a chop. But most of the time I use a Trophy Plus 21, also with added tip cup- for handling, smooth trolling for 'Lunge, and great hole shot. For top end in smooth water I run a 23 Trophy Plus with added tip cup and a leading edge cut- to what the guys running chopper props call an "Allison Cut". I throw a tail with all of these props, but not above the top of the motor for best top end. I do recall several race boats I set up in past years that ran very small props at very high rpm with lower units running 1:1 gear ratios. When set up for top speed all of these rigs would shoot a tail several feet above the motor height- but these race boats are an exception to the rule, since a fully surfaced prop is running in a water/air mix and this less dense medium tends to build up a good sized tail.

So many props- so little time.
Doug

[Edgewalter]

Doug, what do you mean by added tip cup? how does this effect performance?
Ed

[Skeeter20]

In most cases a prop that is a perfect set up at top speed will have a rooster tail no higher then the motor. If you not able to trim that high you arent getting all the potential bow lift out of the boat. Here is a pic of me running last weekend a buddy took as I passed him

[BigGameBalls]

Originally Posted by Skeeter20

In most cases a prop that is a perfect set up at top speed will have a rooster tail no higher then the motor. If you not able to trim that high you arent getting all the potential bow lift out of the boat. Here is a pic of me running last weekend a buddy took as I passed him

Exactly. A huge rooster 20 feet in the air is not good but a boat set up for optimal performance should shoot a rooster about the heigth of the top of the motor. My current set up starts to slip badly and start loosing speed 300-400 RPM before I even get to a rooster.

It also controls the bow like crap in rough water. Instead of holding the bow steadily up letting you glide over and slice through it lets it drop down after every wave causing you to pound into the next one.

[staylor]

An old trick for modding an SS prop involves altering the cup at the tips of the blades only- being carefull not to come too far around into the leading edge. If you go into the leading edge the typical definition is that you've started to "roll the leading edge"- but this is an entirely different modification.

Adding tip cup does two things- the biggest being that you are actually altering the overall rake angle of the prop slightly- giving you a bit more bow lift and in many cases, the ability to run the engine a bit higher on the transom before the prop starts to vent when running on a straight line- especially when in a chop. The second change that comes from added tip cup is a slight change in rpm- added tip cup will drop the rpm slightly since you are slightly changing the pitch of a part of the blade.

The Merc Tempest Plus is a very nice prop design for prop "tuners"- in that at the very tip of each blade Merc has left a small section that is thin enough so it can be bent by a prop shop to add or subtract tip cup. If you look at a Tempest Plus from the prop nut end you can easily see this little section which is essentially left as a sort of "tab".

A typical blueprint of a Tempest Plus for running high on the transom involves adding some tip cup to make the prop bite better. Usually the abiliity to raise the engine another half inch or so before venting comes in will negate the slight drop in rpm from the added effective pitch. The extra bow lift is also a plus, since most bass and walley boats run heavy in the bow.

When a prop shop blueprints a prop they also will regrind the cup on the entire back side of the blade- making a dead square cut at the blade edge- perpendicular to the blade form at the cup- and the grinding is done such that they leave a razor edge on the pressure side of the blade. The now retired Rich Boger at Boger Props down South was a master at this- and even altered the shiny finish near the cup on the pressure side of the blade to try and make the water "stick" a bit and be dragged a bit into the cup. it looked a bit weird with the finish change near the cup- but it sure worked well.

Boger did my Tempest Plus, and I have gotten into the habit of re-dressing the entire cup edge each season- using the old racer's trick of "scraping" the cup with a very hard and very sharp steel knife. There are lots of tricks in the prop rework trade which I've picked up over the past 50 years by simply looking at props by the various shops- or by learning by my own mistakes as a racer. In the days of bronze props I used to add cup by using a trailer ball as a form and a body hammer......works with bronze and heated aluminum- but not stainless!
Doug

[BigGameBalls]

Anyone know a shop in the Twin Cities that demo's Merc props? I'd like to demo this prop and it is what I think it is will be purchasing it.