bobhoffmann

I own a 1988 formula 242 ls. with a bravo 1 drive. The engine flame arrester is the old round type wth the mercruiser sticker that says 454 magnum and bravo on it. The intake is not aluminum and the serial # is b960359. Is this a magnum motor with forged internals or not? I looked up the # and it says 7.4L bravo 88-91, but no magnum

dandercam1

iTrader: (1)

Wouldn't be the first time I have seen a 454 MAG flame arrestor on a 7.4. Look at the Max rpm range shown on the sticker on the valve cover. A 7.4 has a upper limit of 4500rpm and the MAG will be 5000rpm. The 7.4 has a ignition rev limiter at 4750rpm and the MAG is 5250rpm. But even so being a 88 there could be a mismatch of parts being it the valve covers or ignition system so at the end of the day the best tell may be the boats performance. What rpm are you running with what prop? What GPS speed?

bobhoffmann

Just bought the boat. Previous owner said 4800-4900 got 53 -54 gps. More trim and the rpms went up but not the speed. Will have to look for any stickers on the valve covers don't remember any. running a mirage 21. Ignition says thunderbolt.

lakematdude

0B960359 comes up as a MERCRUISER MAGNUM W/ PS 454 BRAVO (454) (1988) Serial No: 0B960359 Model No: 4454110AS

Parts catalog for this serial number,
http://www.mercruiserparts.com/selec...D8+1988%2D1992

You may also want to try and confirm if the serial numbers are the same by checking to see if the Mercruiser engine serial number is stamped into a small metal plate (1" wide X 2" tall) that is usually pinned/riveted to the starboard side of the engine block just above the engine starter towards the rear of the block.
http://www.justanswer.com/view_image...rialNumber.jpg
http://www.google.com/search?q=Locat...ml%3B480%3B640

Griff

1988 engines or any black Mercruiser engines with TB IV ignitions do not have rev limiters.

bobhoffmann

The serial # did come off the tag above starter. Thanks for everyones help, feel better being able to confirm what I was hoping.

dandercam1

iTrader: (1)

What years where the TB IV ignitions used?...I had a 96 7.4 that was rev limited to 4750

mcollinstn

No aluminum high rise dual plane intake = no magnum. Period.
If a magnet sticks to the intake, you have a 330hp cast 454. End of story.

1988 TB IV = no rev limiter.
1996 = rev limiter.

MC

ext2gtx

I believe my 87 said mag, but is really a 330 hp but they still called it a mag.

Pliant

http://www.4shared.com/document/TcRI..._SN_range.html

http://boatinfo.no/lib/library.html

Manual 9 page 221