1987 242ls 454 magnum prop performance
 

I currentlyhave a 1987 242 ls with the 454 magnum with a mirage 23p prop. Any suggestions/ comments about this prop and pitch. I believe the max rpm for that motor is 4800 rpms. Right now the highest is 4300 reps. I’ve read other post on off shore and some owners believe a 17 pitch would be better but my concern is over reving. Also does anyone have any comment/ suggestions about Four blade versus three blade. I’m very new at this I/O and big block boating. The motor appears to run well.

As always any help is appreciated.
Regards,
Tony S

The 21p mirage plus would be what came on that setup to get 4800 rpm.

Personally I would put a 21p mercury revolution on it. The revo (4 blade) planes, turns, and all around handles the boat much better than the m+ will. I've ran quite a few wheels on my 242 and in my experience the revo is the best all around prop. The mirage is a touch faster on the top end, but the handling at all other rpm makes the revo a better option in my experience.

i agree with this. I had a 1988 242ss 454 bravo. And the 23 is too much.

2 important unique things to keep in mind here. 1987 454 Mag is 330 hp peanut port NOT a Mag. 1987 has an ALPHA drive NOT a Bravo 1.
May want to check with MASI 242 he ended up with a 19 REV 4 prop for his.

The 454 330 hp mag/alpha had/has 1.36 gears, instead of the 1.50, too, right ?

Yes sit that is correct.
Hence even a smaller pitch is in order. i.e. 19 Rev 4-4 blade and easy out of the hole, please.

Both great points above! Tony, do you have an alpha or has someone swapped it to a bravo? What is your gear?

When i had my 242 it did have the Alpha 1.5 ratio some will come with 1.32 gears, Gary i can`t remember what size the rev was never got to try it, but i would try one four blade is the way to go in my opion. Good luck

Max RPM for the 87 454 Mag (330 HP) is 4600. The 88 and above is 5k.

You do not want to run the 330 over 4600 for too long. The rods and especially the rod bolts are the weak link and do not tolerate high RPM.

In my opinion you’re probably propped about right. Are you trimming it out? Dropping to a 21P Mirage Plus will probably put you right at 4600.

My 89 242 454 Mag came with a 23P Mirage per the factory invoice... the drive and prop had been stolen when I got it... I went with the same prop and ran 56-58 4700-4800 depending on the weather.

** I would verify the RPM with a digital tach. The old VDO could be off.

All 454 mags in 87 to 90 where rated at 365 hp at the prop.
the 1988 bravo 1.5 330 hp 242 would do 54 mph on the speedo mirage plus 21p. 50 ish radar Per factory.
the mag would do 52 radar factory. Mirage plus 23p. Alpha 1.5

An Unusual mistake by Oconnor.
Look at this thread, especially post #8 from a VERY knowledgeable, BANNED, member.
https://www.offshoreonly.com/forums/...do-i-have.html
Also from a thread in SpeedWake:
In 1987 ONLY. The 454 Magnum was just a 330.

In 1988 The '87 Magnum was now the 7.4L (330) and the new Magnum was the old 370TRS motor now rated at 365 hp.

All of the 454 Magnums in 1987 had an Alpha drive. It did not hold up to the big block and the Bravo was born in 1988

To answer Red Hots question, In 1987, to get a motor with more than 330 hp (370 was the next step) it was packaged with the TRS drive and a Borg Warner tranny. When they introduced the 454 Magnum/Alpha in '87, big block power was now available in many smaller boats that did not have the room for the engine and tranny.

So, in '87 only, if it did NOT have a TRS drive all big blocks were just a 330.

I and MASI242 both had 1987 454 MAG motors, we both know what they were. I tore mine down and verified.
Peanut port, small rods, cast everything, 2 bolt mains.
Good luck. 330 at the flywheel, maybe less.

What i wrote is correct.
Sierra Marine Parts Catalog

That catalog is wrong.

whats wrong with it?

It has no listing for the ‘88-up 454 Mag Bravo (MK-IV). The ‘87-88 454 Mag Alpha is not the same as the ‘88-up 454 Mag Bravo. Is it lumped under the 7.4L Bravo?

Side by side the ‘87 454 Mag Alpha is a dead ringer to the 7.4L 330.

Just saying is all.

ive never seen a 88 mag bravo.

🤔🤔

Did you click on intake manifolds ?

1,000 words.
I Ain't seeing any Hi-Rise Intake Manifold.
https://cimg3.ibsrv.net/gimg/www.off...f71d87c147.jpg
https://cimg7.ibsrv.net/gimg/www.off...f66bdc89c6.jpg
https://cimg0.ibsrv.net/gimg/www.off...9ca9f329b9.jpg

I can’t remember right now but there where a yr or two on some low hp 454 engines rect intakes where found on oval heads. I’ll see if my brain starts working sometime today.

Maybe Conner is speaking of those.

Engine Merc did this (rect port intake small oval heads) to was fuel injected. 1995/96 Gen V (pre-L29) 310HP 7.4 .

I did clean my bilge up a little.
https://cimg0.ibsrv.net/gimg/www.off...cf397353c7.jpg
https://cimg1.ibsrv.net/gimg/www.off...751a566247.jpg
https://cimg4.ibsrv.net/gimg/www.off...e0dfd50ea8.jpg

??🤔

Have you been paying attention to this thread ? LOL.

??🤔

A family member has A Scarab II also with these 454 330 Mag Alpha original engines in my cove. Should I go take a pic later and post ??? Or ????

[QUOTE=SB;4746850]A family member has A Scarab II also with these 454 330 Mag Alpha original engines in my cove. Should I go take a pic later and post ???



330 hp mag?
never heard of or saw a "330 " mag.
Never heard of or saw a 1988 mag bravo either.
Must be special ones

Officially it is labeled as 454 Mag / Alpha.
Click:
https://www.mercruiserparts.com/454-...8-1986-1988-0a

The 454 is the 330 hp version.

You said the mag was 330 hp?
I never heard or saw a magnum 330 hp.
365 hp 454 magnum is what i have seen with alpha

This is like arguing with a 12 year old girl.
If I haven't seen it it must not exist. RIGHT

On the original subject line, Mr. Tony have you tried any other wheels yet?

https://www.perfprotech.com/mercury-...-8%201988-1992

And ....He was adamant a little boat I work on / tune doesn't go over 70mph with the engine it has. Lolololol.

??🤔

??🤔

thanks.
I cant find where is says the magnum was 330 hp. Like someone claims.
My understanding was they were 365 hp

Mercruiser most definitely built a 330HP Alpha Magnum. It quite literally was nothing more then a small head cast internal 330hp 454. Totally weird deal they did only in i think 87 and maybe 88 but it did exist and they were only coupled to an Alpha . . . not sure what Merc was thinking with that move but it did not last long. the Merc Bravo/Mag starting in 88/89 was a 365hp big port forged internal 454 that was actually a hellofa motor :D . . .my 88 Scarab III had Mags and were 365's on Bravos (first year)

Now Dave’s in trouble too.

ooooo

:)

And you want to report everyone's posts to the Mods because people are saying mean things to you and are harassing you???

Maybe you should accept the fact that you are WRONG and stop arguing.