Re: 4 - Blades on Older Formulas
 

I too spoke with the late great Mr. Cavanaugh (yes he was very nice guy to talk to), and he and his successor (forget his name) said to use Mirage Plus as well.
However, here's the deal, been discussed here before. Mirage is a STERN lifting prop. Bravo 1 is a BOW lifting prop. Bow lifting props work best on stepped hulls with twins, and some singles. Our old twin boats typically need STERN lift. Now Merc does not make a STERN lifting 4 blade, they only make the Bravo BOW lifting, and Merc is never going to recommend you go use someone else's props.

Hydromotive for example makes two versions of their 4 blade, the Quad IV, and the Quad IV-X. The Quad IV is a STERN lifting prop aimed at older, non stepped hull designs. The Quad IV-X is a BOW lifting prop aimed at newer stepped hull designs, basically their copy of a Bravo 1 prop. There are other manufactures who do the same thing, just not Merc - they basically turned their backs on the older boats and did not spend any R&D on making a 4/5 blade design for them.

Re: 4 - Blades on Older Formulas
 

OK, so who has all stock 311 w/454 mags and Quad IV's? how much if any more mph? Don't really care about hole and mid range. Tanx

Re: 4 - Blades on Older Formulas
 

Hey Jaybird, thanks for the advice on the winter cover, its working great and I keep the rear open to moving fresh air - no mold!

Re: 4 - Blades on Older Formulas
 

OK Outlaw,,,,,,,,,,, that's your que. Cut and paste your boiler-plate 500 word essay on the results of your Quad IV installation :D :D

But seriously, Outlaw claims huge gains with Quad IV. I'll be following his lead soon.

By the way Outlaw, got the ladder. Thanks for the deal buddy. :drink: :drink:

Re: 4 - Blades on Older Formulas
 

Glad to hear it's working out! The best part is that once you spend the time the 1st time to get it set up right, next year is a snap, and no annual $$ invested on stupid shrink wrap.

BTW - my winter cover is working out great too - it's called the regular canvas cover :p !

Re: 4 - Blades on Older Formulas
 

Glad the ladder finally arrived, hope it passed the "Third" inspection of quality....:D Put some white rubber caps available at any hardward store over the ends of the tubing and it'll look brand new from four feet away. (don't forget to polish the mounting nuts, I forgot to do those....:D

Reader's Digest condensed version:

My boat is an 89' 311 with, according to original build sheet, with 454 mags. It came with Mirage 23" props. Ran the boat for about four months with the Mirage. Had a very long conversation with Hydromotive, they told me what I could expect in changing over to the Quad IV's. They were very patient with me and answered all my dumb questions. They hit the results EXACTLY and the Quad IV's did exactly what they said they would do. It increased my cruising speed by 6/7 mph (gps) at 3,300 rpms or thereabouts. It increased my top end by 3 mph and the boat at speed felt it was running "easier" if that makes any sense. With the Quad IV's getting up on plane was effortless compared to the Mirage props. Midrange punch was noticeably stronger. The first time out with the Quad IV's even my wife immediately noticed the difference. Note: this was all with the Silent Thunder box still on the boat.

I've since removed the silent thunder box, changed the exhaust from the stock junk Merc units, to EMI Thunder aluminum tuned exhaust. The stock Merc units just dump the exhaust gases into one big "cavern" and eventually the gases find their way out, extremely inefficient. The new EMI's have seperate tuned runners, much MORE efficient. There is no engine made that would not see some type of performance increase with that change. Rule #1 in motors: you can never pump more fuel into a motor than what you can exhaust out.
So off comes the silent thunder system and installed the new exhaust from EMI and new tips from Stainless Marine with the Superflapper courtesey of our very own Too Old at Trick Marine, THE BEST guy in the world to deal with. BAR NONE... :drink:

With the new exhaust in place here is what I've noticed so far two times out: One, it does not jump up on plane quite as easily and it was I believe Thirdbird who came up with the reason. The silent thunder box actually acts as an additional trim tab because the back of the box is DEFINITELY hitting the water coming up on plane. With the box gone, that "tab" is gone. Once up on plane though, it's a whole different story. The boat feels stronger throughout the entire speed range. And as a side note, under 38/4,000 rpms it isn't much louder in the cockpit. You can easily carry on a normal conversation or listen to tunes. Over 4 grand it starts to get loud and over 5 grand it is very loud. Top speed runs last time out: just me in the boat and half a tank of gas or so, no extra crap on board, going north in Sarasota Bay with a 2 ft. chop head sea I saw 72 mph on GPS. Going south in Sarasota Bay three hours later, running in a 1 ft. following sea, I saw 74 on GPS. This difference could have been tide, wind, whatever.
Also, the drive trim reacts much quicker than before. In losing the silent thunder box, and the difference in weight between the EMI aluminum exhaust and the stock Merc "anchors", I lost at least 500 lbs sitting right over the props. My boat when docked now sits at least two inches or more higher out of the water. Next time your guys boats are docked, get two 250 guys to stand on the swim platform at the same time and notice how much lower the stern is. That's how much higher mine is now.

When I first bought the boat 64/65 was the best I could get out of her with the Mirage props and the silent thunder and stock Merc exhaust in place. So between the prop change and the exhaust change, I gained damned close to 10 mph all by GPS.

Now if I can just swing some new motors.....:D



Sorry Dave, I know this is probably close to 500 words. :D

Re: 4 - Blades on Older Formulas
 

Quick follow up:

One thing I've learned on my own and then reinforced by watching and listening to the racers. A boat seems to run faster if it is running higher out of the water YET flatter. A boat that is running "bow high" means the stern is lower in the water which is going to increase drag and slow you down. I used to run my 242 with twin small blocks as bow high as I could get it thinking it would run faster with less boat in the water, them somene suggested I try running it flatter, and whoa, I picked up 3 mph. Talking about feeling stupid......:eek:

After that I really watched and listened to the commentators on any of the boat racing programs to study how racers trimmed and drove their boats. Figured they knew a hell of a lot more than I did. :drink:

Re: 4 - Blades on Older Formulas
 

Thanks for the "condensed" version :rolleyes: :D
before I call Hydromotive with my dumb q's, did you replace with 23p?
Anyone have a used set??? This isn't starting out to be a year with a lot of discretionary funds.

Silent Thunder - when mine inevitably goes to crap and the inside starts to flap and vibrate I'll trash mine too. at the least its less to trip on.

Tanx

Re: 4 - Blades on Older Formulas
 

Doh!!!!!!!!!

There it is, the "quick follow up" just sent it over 500 words. :D

Outlaw is not a man of few words :p

Re: 4 - Blades on Older Formulas
 

I will admit, that at times, I have been accused of having a big mouth. :eek:

I want to respond that is only "viscious rumor"....:D :D