5.7 gen2 to 5.3 gen3 swap?

**lowlow62** · 08-18-2010, 07:07 PM

i have a friend who wants to swap out engines in his boat i have no idea what brand of boat this is its some kinda deck the hull id# is USPA98DBB696 any info would help . what i want to know is has anybody done this type of swap and what is all involved it has a mercruiser 300 ouit drive if this helps..... thanks

**BDMarine** · 08-19-2010, 09:09 AM

The only package Mercruiser ever had with a "300" is the 300 Tempest in '85 & '86. It would be an Alpha One.
I am not familiar with the 5.3 Vortec as afar as engine mounting. Items of concern would be the front mounting hole pattern and location, bellhousing matching up to the block, does it have a manual transmission type flywheel to allow the coupler to bolt to it, will the exhaust manifolds bolt up to the heads, etc.

**IMPATIENT 1** · 08-19-2010, 09:12 AM

the rear motor mount for the 5.7 will bolt up to the 5.3 with alil clearence work, no biggie, but the frt mounts are alot different. its not hard at all to build frt mounts for the motor

**Dave Strong** · 08-19-2010, 05:16 PM

I think you would be further ahead to do a 383 stroker kit to the 5.7 over putting a 5.3 in. When the 5.3 first came out I worked at GM dealer and most the customers that went to the 5.3 from a 5.7 said they liked the 5.3 better untill they hook their 5th wheel to the truck and said the 5.7 was better for pulling. Torque was better in the 5.7, torque is real important in a boat. JMO.

Dave

**lowlow62** · 08-19-2010, 08:55 PM

yeah i kinda figuered the torque could be a problem but this guy is hell bent on doing it so f&*k it his money ,the front mounts look really easy to make work the one thing i noticed was the 5.7 has a flywheel and the 5.3 has a flex plate how nuch is this going to affect it you think? i already sent the flex plate out to get drilled to fit the pto and we should have this all put together this weekend what about headers do they have to be water cooled from the bottom by the heads or can i just dump out by collecter? thanks i really appreciate all the help

**"Flat" foot'n** · 08-20-2010, 06:45 AM

Originally Posted by Dave Strong

I think you would be further ahead to do a 383 stroker kit to the 5.7 over putting a 5.3 in. When the 5.3 first came out I worked at GM dealer and most the customers that went to the 5.3 from a 5.7 said they liked the 5.3 better untill they hook their 5th wheel to the truck and said the 5.7 was better for pulling. Torque was better in the 5.7, torque is real important in a boat. JMO.

Dave

My wifes 04' Trailblazer 4x4, it has a 5.3 in it with the 3.73 rear end. Belowe 4000rpm it's a F'n pig. I would like to see a dyno sheet on this motor.
With how lazy this thing is at the lower rpm's I'd NEVER consider putting it in a boat. I don't know if it's a ECM MAPing issue or if it's just the mechanics built in. I bought a Diablo tuner and cold air intake, still a pig, but now it has lipstick on

Do you know any torque #'s?

**IMPATIENT 1** · 08-20-2010, 06:54 AM

u guys are a trip, hate to tell ya but the 5.3 with a carb and msd 6010 c.o.p. ignition we eat a 383 up in tq and hp, with nothing more than a cam change to the 5.3 lol. betr askkkk somebodyyyyyyyyy

**lowlow62** · 08-20-2010, 07:34 PM

the tunning part is not a problem I've got a buddy who has efi live and is a pretty good tuner . these ecms have a lot of torque managment built in thats why they suck in stock form when you put a carb on them they scream, a lot of guys here are doing engine swamps to ther jeeps and anything else they get there hands on , i was more worried about how to prep a truck engine for marine use if such a thing exsist or just bolt it in and run it

**"Flat" foot'n** · 08-22-2010, 10:58 AM

Originally Posted by IMPATIENT 1

u guys are a trip, hate to tell ya but the 5.3 with a carb and msd 6010 c.o.p. ignition we eat a 383 up in tq and hp, with nothing more than a cam change to the 5.3 lol. betr askkkk somebodyyyyyyyyy

I don't dought that a bit. Once the 5.3 hits 4,000rpm it's an ANIMAL. I really need to get this thing tuned. My buddy had his LS7 Z06 tuned. With out the torque managment...It walked away from my stock LS7 Z06.
I would like to put a LS7 in my Barron Sprint

**LSXINDUSTRIES** · 09-08-2010, 08:56 PM

Originally Posted by IMPATIENT 1

u guys are a trip, hate to tell ya but the 5.3 with a carb and msd 6010 c.o.p. ignition we eat a 383 up in tq and hp, with nothing more than a cam change to the 5.3 lol. betr askkkk somebodyyyyyyyyy

5.3 + small cam = certified 383 killer! Of course if the 383 has a set of AFR's on it.......we might be in trouble! Then again....the 5.3 with the cam swap cost's less than a set of AFR heads alone!

**lowlow62** · 09-09-2010, 06:16 PM

ok set the motor in today bolted it all up everything seem to line up just had to move the motor mounts back an inch . my question is does the alpha 1 drive have its own water pump to supply motor or does it need a seperate water pump ? and i route it in like a jet boat into block first then out the thermostat housing or in this case out of heads and into exhaust ?

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5.7 gen2 to 5.3 gen3 swap?

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