Merc 7.4 LX (TBI) potential?
05-07-2022, 12:04 PM
#12
Platinum Member
Platinum Member
iTrader: (2)
Depends on the year. Can be a Gen V or VI. Gen 5 would be flat tappets; Gen VI, roller with the resulting hardware. My assumption was a Gen VI. The block itself was more a focus than anything because it would be a 4-bolt.
Your 96 I’m guessing is a Gen V, right? Stamped steel timing cover?
Your 96 I’m guessing is a Gen V, right? Stamped steel timing cover?
05-08-2022, 10:03 PM
#13
Charter Member # 55
Charter Member
Howdy folks, new guy here.
I'm looking at an older boat that was repowered recently (last 10 years) with a 7.4 LX and a Bravo One. The boat is nothing special, but the engine and drive are what I'm looking for to repower my current boat.
I know this Merc is rated at a measly 300 horsepower and I'd like to do a mild performance build, say 500 NA horsepower. It was suggested (by a member of Classic Offshore Boat Restoration on Facebook) that I ask here.
What are the drawbacks to the Gen VI block, regarding performance? I've read they're a slightly thin casting, boring 0.125" isn't possible, but I don't think I'd need an 1/8" bore to make decent power. How are the heads on these? Ample for 500 horsepower, or should I be looking for better heads? I've read some conflicting info, but it seems that these engines have a cast crank. Is throttle body injection sufficient?
Help me out, if you would please. I've built a few hot rods in my time and have had a handful of boats, but never really gone this far in the boating world.
I'm looking at an older boat that was repowered recently (last 10 years) with a 7.4 LX and a Bravo One. The boat is nothing special, but the engine and drive are what I'm looking for to repower my current boat.
I know this Merc is rated at a measly 300 horsepower and I'd like to do a mild performance build, say 500 NA horsepower. It was suggested (by a member of Classic Offshore Boat Restoration on Facebook) that I ask here.
What are the drawbacks to the Gen VI block, regarding performance? I've read they're a slightly thin casting, boring 0.125" isn't possible, but I don't think I'd need an 1/8" bore to make decent power. How are the heads on these? Ample for 500 horsepower, or should I be looking for better heads? I've read some conflicting info, but it seems that these engines have a cast crank. Is throttle body injection sufficient?
Help me out, if you would please. I've built a few hot rods in my time and have had a handful of boats, but never really gone this far in the boating world.
05-09-2022, 11:39 AM
#15
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iTrader: (1)
There’s potential in a 454 tbi engine ?
05-09-2022, 03:33 PM
#16
Registered
Someone please correct me if I'm mistaken, but I believe the 7.4LX used the same intake, throttle body and components and the 454MAG and 502MAG EFI's. With that being said, it certainly has way more potential than a typical 7.4 MPI?
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daddio211 (05-09-2022)
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daddio211 (05-09-2022)
05-09-2022, 04:40 PM
#19
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Thread Starter
So I think I'm going to buy the engine and drive. Before it goes into the Sleekcraft I'll pull the pan and heads and take inventory of what's there. If it's a 2-bolt main I'll plan to have my machine shop drill for a 4 bolt main, splayed if possible. I truly appreciate all of your help.
05-09-2022, 04:42 PM
#20
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Thread Starter
