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Discussion Starter · #1 ·
ok i am kinda new to both the board and to boating...i purchased a 88 242 formula at the end of last year and i damaged the prop 1st time out this year...i have gotten the prop repaired but in doing so i think something has changed...the rpms are higher now after the prop has been reworked when i am running w.o.t. and they are going above engine recomended specs...i would like to purchase a new one and keep this as a spare...can anyone point me in the right direction to where i can buy one at a reasonable price...and i guess what would be a reasonable price??? prop that is on it now is a mirage plus 21p
 

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Couple questions first. What do you have for power? What rpm's are your spinning with the 21?

If you are looking for another Mirage Plus you should pay around $430 - $450 for one. Most marine stores will carry them. If their prices are bad you can get them online for those prices from multple different sites.
 

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Discussion Starter · #3 ·
engine has 330 hp...at the end of last year i was turning 4600 - 4800 rpms and this year it wants to turn 4800 and up after i had the prop fixed after i get the boat all trimmed out...now i also put new plugs, wires and dist cap on before i put it back in the water this year...
 

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Sounds about right, actually. Remember that the boat prop is determined by a number of factors, and a big one is weight. When you ran this year, how many people were on the the boat? How much gas? MSD hooked up? H20 tank filled? Cooler on board? 300 - 440 lbs makes a difference. You'd also be suprised in the difference in performance you can get between a hot humid day in the summer, and a cool, dry spring day.

I have a '89 223 Formula with the same motor (330 hp 454). Don't recall the pitch. All by myself, running on fumes on a cool spring/fall day, I'll top out at 5000rpm and 55mph(don't do that too often!). But in the summer, with 3 - 4 peeps on board, fully fueled, with cooler(s), I run WOT @ 4500rpm and 50mph.

Hopefully you got the same prop back as you sent, 21 pitch sounds right for your boat. You may want to contact Formula and confirm the proper pitch.
 

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I think spinning it 5000 is a little too high. I'm not positive on that engine as I have a pair of 350's in mine. I spin 21 Mirage Plus's as well and get about 4600 rpm's out of them all trimmed out. You might want to borrow a 23' Mirage Plus from someone or maybe try a 21 4 blade Hydromotive and see how your boat handles. If you check out the forum at www.offshoreonly.com there should be someone that would let you try some props out if you can't find anyone from here that has some laying around.

By the way, Damn Yankee is right. Weight, water and air temp all will make a much bigger difference than you think.
 

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Discussion Starter · #6 ·
i was out friday by myself with 1/2 - 3/4 tank of gas, no water and no other equip...turning 4800 rpms, 47-48 mph (gps), and 1/4 - 1-8 throttle left...did not want to get the rpms any higher cause the tag on the engine states that rpm operating range is only 4600-4800...dont need to break anything...last year i was turning 4800 rpms with 1/4-1/8 tank fuel with 2-3 peeps, equip and getting 51-52 mph (gps)...also to get those rpms last year i needed to raise the out drive up a little bit...this year it was fully down and of course when i raised it the rpms would go up too...what is MSD?...and i contacted formula and they told me that 21p is the prop that came with the boat and that they recomended...could my prop possibly be out of pitch or possible diameter change when they fixed it? i hit something 1st time out this year when i was coming back in to take the boat out...bent two of the blades and took a little bit out of one of them...and thank you for the help...
 

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Try Henry Smith's in Algonac. They have almost everything in stock and I think they can help answer alot of your questions, especially since all they do is prop work.
 

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i agree with everything that has been stated above. but i think it also depends on how badly you damaged the prop before you it was repaired. if the place you took it just filed the edges and added materiall they may have messed up the pitch. Especially if you hit the ground or whatever hard. i did the same thing you did on my first time ever out with this boat last year, and i wound up sending the prop to Hydromotive in Ohio for repair b/c they have some sort of electronic machine that allows them to get the prop to the original pitch during/after repair. i have the same motor in my liberator and i spin a 20, but it is an OMC. i usually run about 4800 rpm wideopen and trimmed out.
 

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mcdougal34,

Just how new are you to boating? I ask because from what you've said about trimming your boat, sounds like you could use some tips. I don't mean to offend, just wanna help if I can!

Also, 1988 is the 1st year that Mercruiser offered the 454 Magnum rated at 4800rpm and 365hp. Are sure it's not? I ask because your numbers for that boat are around what I get, and you got 2 feet and at least 500lbs on me! Sounds like you got more hp, or maybe I got issues that I didn't know I had... Is your drive a Bravo or Alpha? Some of the early Magnums were mated with Alphas...

One more thing, MSD = Marine Sanitation Device otherwise known as a porta-potti.
 

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Discussion Starter · #10 ·
this is my first boat...dad has always had a boat though...i dont know...my uncle had the same boat except for he had the LS and i have the SS...he ran almost the same as i am 4800 rpms and around 53-54 mph...in 1 ft chop...and i dont know if this is the most correct way to get the most out of my boat on a calm day but trim tabs all the way up and i have found the best speed for me is raising the outdrive up just a little bit to try and get the bow up...and i am sure that i have 330 hp...i wish i had the 365hp...and i have a bravo outdrive...i think i am going to try and find someone who has a new 21p or a store that will let me try it out...are there any shops around lsc that will do this...
 

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I checked my Mercruiser manual and the 7.4 liter max rpm is 4200 - 4600rpm. The Magnum 4400 - 5000. I really think that you should wait until it gets warmer out. You're gonna want every bit of rpm this summer, and I'd bet that you lose 400rpm or more at WOT in July with a full load!

Sounds like you got the trim figured out, sure is a great feeling to play with it and get it trimmed way up out the water, isn't it?

How much does your boat weigh?
 

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Okay, branch of the topic tree here.

I have a 1988 270 Sundancer with twin 350's (5.7 Merc's) with alpha drives. How do I figure out what I should be running at WOT verses what I am actually running when I cant run it any harder (both rpm and mph)?
Also, besides telling from the seat of my speedo's, how do I find the best cruising speed for the distance hauls across the lake or over to Lake Erie? (again in both rpm's and mpg)

Thanks,
Jim
 

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Discussion Starter · #13 ·
yeah its nice when it finally gets out of the hole and on plane...its a dog getting out of the hole...lol...i think it weighs around 5200 lbs loaded...at least that is what the guy told me when i bought it...i think i am going to have to call formula again to get those numbers too...hey damn yankee what color scheme do you have on your boat and where do you guys usually hang out at? i have large teal strip with thin black and grey strips along water line...
 

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Mine's got Red/Gray/Black hull, black swim platform. My boat tips the scales at 4000lbs, either your boat don't weigh 5200lbs or I got a performance issue with my boat. Same engine and 25% lighter should = more speed.

Lots of places on the Lake to hang, depends on what you wanna do. This is my 3rd year on the lake, and the 1st 2 years I didn't get out hardly at all. So, to answer your question as to where I go to hang, I only been to a few. There's Strawberry island, Gull island, and Muscamoot bay. There' s usually a $h!t load of boats there. But, like you being new to the lake, I don't really know any people who have a boat, so I haven't really been to those places when it gets crazy. Not that I'm antisocial, tying up with a few boats and partying is great, if you know someone to raft with! With all the peeps that I've met on this board so far, I'm sure that won't be an issue this year.

I'll be out this weekend, there's a thread on the 'Boathhouse' forum about partying at Gull island Saturday, weather permitting. Gonna make a serious attempt at participating.

Then there's the restaurants: Jack's, Tin Fish, Browns, Decker's, Beach club, The Raft, and I'm sure ther's more!
 

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Discussion Starter · #15 ·
damn yankee...just called formula and they told me dry weight for my 242 is 4150 lbs and it has 107 gal gas tank...he also told me 89 223 dry weight is 3750 lbs with 85 gal gas...also when i have 3/4 to full tank with 2 peeps i get 47-48 mph (gps) in 1ft chop...and thanks for the info on the lake...
 

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QUOTE(PyrateJim @ Jun 4 2003, 01:10 AM)Okay, branch of the topic tree here.

I have a 1988 270 Sundancer with twin 350's (5.7 Merc's) with alpha drives. How do I figure out what I should be running at WOT verses what I am actually running when I cant run it any harder (both rpm and mph)?
Also, besides telling from the seat of my speedo's, how do I find the best cruising speed for the distance hauls across the lake or over to Lake Erie? (again in both rpm's and mpg)

Thanks,
Jim
Jim, I don't know about twins, but on both of my boats with single 350's cruising RPM was between 3300 and 3500. That was keeping it out of the four barrel. It also depends on water conditions. But generally thats where I keep it for steady cruising. Not sure but I'd guess it will be pretty close for yours too. That will give you the best fuel economy and best cruising speed for long hauls. You have to get used to the sound and feel of your boat to really tell. Only way to realistically do that is time on the lake. Thats the fun part.
 

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mcdougal,

Personally, I wouldn't lose any sleep over running a non-mag 454 at 5000 rpm's. I've seen many modified non-mag 454's run at 5500 for many, many seasons. I personally run a significantly modified 454 MAG EFI at 5400 rpms, even though the manufacturer recommends much less. Sure, the non mag motors don't have the forged crank and piston that its big brother has, but I wouldn't think this makes too much of a big difference in stock applications. I would try spinning the motor to 5000 rpm, the motor probably wont make much more power beyond that.

As for why the RPM is so different, I would have to think that the prop "repairman" might have had a bit to do with that. If the edges of a blade are nicked, most repair shops will simply grind down the edge until the nick is gone. This reduces the surface area of the blade. To properly balance the prop, all other blades would most likely be "trimmed" down to the same size. This also would most likely reduce the overall diameter of the prop.

Reducing the diameter of a prop is a very simple technique many racers use to pick up a few extra RPM's out of their motors. The smallest diameter decreases will yield noticeable RPM increases. If I was a betting man, I'd put money on the idea that your diameter has decreased slightly.

Another good point that has also been brought up, is operating condition. If you've noticed the RPM increase just this year only, I would once again bet that the air temp was most likely 60 degrees... tops! Cool air makes good horsepower. A 30 degree temperature difference will account for 300 RPM's in my engines alone! Also, load up the boat with gas (110 gallons for me) people, beer and gear... I will easily lose another 100 - 200 RPM's.

Ask around some of the local marina's for demo props. Some of the nicer establishments will let you take a wheel for a test spin. Some may require a deposit, some may not.

Good Luck

-Bayley
 

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Discussion Starter · #18 ·
thanks for the help every one...bayley...do you know of any specific marinas in the area (st clair shores - algonac) that will let you take a wheel for a test spin?
 

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I agree with Bayley. The most likely situation is the repair shop reduced the diameter as an easy fix and you have more rpm. Cooler weather also helped.

I thought MSD was multiple spark discharge?
 
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