Repowering a 242LS

[chewymalone]

My offseason project is going to be a repower of my 1990 242LS. I currently have a stock 454mag with Stainless Marine exhaust and EM flame arrestor which spins a 23 Mirage at 4600 RPM and 55-56 MPH.

I'm thinking of rebuilding and hopping up my 454 and/or adding a Procharger. My other option is to sale the current motor and drop in a 500HP.

Anyone have experience or opinions on this? What top speed would you expect from these set-ups? I want the boat to remain reliable, but I'd like to see 70+ MPH. If someone is running a 500HP or a Procharged 454 in a 242 or a 271, it might give me a reference point.

Thanks!

[mopower]

I have some exact figures from my buddys spring time repower of his 91 242LS. Had a 502 Mag/23 Mirage wot 61. Changed to labbed 24" Bravo picked up6 mph at 3000 rpm and 5 mph at 4000. 1 mph at wot or 62 mph at 4800/4900 rpms. Rebuilt an HP500 to 535 hp(dyno) and tops out at 70ish GPS. 71/72 speedo
He's still running the labbed 24" Bravo but at 5500 rpm. Tried a stock 26" and lost speed and rpms .
This should give you a first hand idea of what to expect.
Long story , short , you'll need 525 to 550 to break the 70 mark

[R-Don]

I was thinking about repowering my 242 & changing the BBC for a pair of smallblocks.

Has anyone done this conversion?

Is it possible?

And what structural work would be necessary?

Anyone have any pics of the bilge of a 242 with its two motors removed?

[R-Don]

Hey Mopower,

How reliable is your mates engine likely to be?

What other options of engine would make a reliable 550hp?

[mopower]

Originally Posted by R-Don

Hey Mopower,

How reliable is your mates engine likely to be?

What other options of engine would make a reliable 550hp?

Should be every bit reliable as a Merc HP500. All HP500 parts except the cam. It's one step up from the original and 1.8 intake rockers and 1.7 exhaust rockers. Gil exhaust and FWC

[mopower]

Originally Posted by R-Don

I was thinking about repowering my 242 & changing the BBC for a pair of smallblocks.

Has anyone done this conversion?

Is it possible?

And what structural work would be necessary?

Anyone have any pics of the bilge of a 242 with its two motors removed?

Anythings possible but is it worth it? Alot of work and major expense. Yes structural work is necessary.
It would be cheaper to trade up.
I considered it when I had my 211 Liberator. Removing the BB and bracket mount two big outboards. Nixxed the idea

[R-Don]

Thanks for that Mopower,

I think ill look at the HP500 route then.

[chewymalone]

mopower-

Who built your friend's motor and what was the approximate cost?

[cuposterchild]

If you are really serious about a 242 SR-1 with twins then there is one on ebay that looks really clean. I have some picks of a 242 setup for twins with the engines out...I will look for them. Here is the link to the 242 on ebay....looks pretty good

http://cgi.ebay.com/ebaymotors/Formu...QQcmdZViewItem

For 16,900 even without trailer is seems more reasonable than what some are asking for a single 242 with a 454 mag

[mopower]

Chewy,

It's a long story. My buddys brother GAVE him a cannibalized HP500. Most all the major stuff was there. Added new pistons , cam , lifters , springs , valves , push rods , bearings and oil pump. Was missing intake , carb and flame arrestor.. Another mutual friend has an engine shop and he did the machine work and balanced the rotating assy.
My buddy and I assembled it and took it back to the machine shop for a few dyno pulls. Not to make you sick , but he probably has less than $4000 in it including new Gil Marine exhaust manifolds and found nice used risers