Need advice on replacement 5.7 Merc

[Streffpilot]

So.....I got a 88 Glastron 19CSS Carlson, (full project) and just tore the motor down today.....the heads were all rusted as were the cylinder bores.

So I need a new motor. This is where the questions come in. Can I buy a used one out of the same vintage chevy truck? I have the exhaust risers and such are all in excellent condition on my motor, so I can swap those over. What about cam, heads, intake, and carb?

I have no carb....so I definitely need one of those......but as far as the rest of the parts what would I need. I think if I got a 5.7 from a 97 or 98 chevy truck they have the good vortec heads right?

Thank you for your guidance!

 

[thumpar]

A truck cam will be close enough that it is fine for boating. The heads are the same for boats. Most intakes, especially later, will not work because they are not for carbs. You will need a marine carb. Other things to change are core plugs, water pump and all "externals". Head gaskets are usually recommended to change also.

 

[Scott Danforth]

Since you need a new motor, find a '96 or later vortec truck motor and pick up a bit more power.

As Thumpar stated, change the head gaskets and core plugs. Cam only if you want

 

[alldodge]

Can I buy a used one out of the same vintage chevy truck?

If you get a pre-vortec motor then all your stuff will bolt back up.

I think if I got a 5.7 from a 97 or 98 chevy truck they have the good vortec heads right?

If you get a vortec motor then will need some bracket changes. Any truck motor will work

The other parts needed have been discussed

 

[Streffpilot]

Now another question.....What about the new LM series GM truck engines? I know the exhaust manifolds are different.....what else would need replacing? or is that not worth the effort. I can find 6.0L in my area fairly easily.

 

[thumpar]

The 6.2 was marinized but not the 6.0. I don't know if they used the LM block or the LS block. Either way you would need closed cooling, fuel injection and LOTs of other parts from the marine version that would get very expensive very fast.

 

[Scott Danforth]

Both the 6.0 and 6.2 LS motors have been marinized along with the 5.7 and 5.3

 

[Streffpilot]

ok....so I will look for a 96-99 chevy truck with a 5.7.....I dont mind making new brackets, but I dont want to deal with the problems you point out in the LS......

How much power could be expected from the 96 and newer vortec 5.7?

Thank you for the help by the way!

 

[achris]

Carbureted, around 280. Multi point injected, 300...

 

[Scott Danforth]

Carbureted, around 280. Multi point injected, 300...

and that is prop HP

even a bit more if you change the cam and add a carb spacer (or change the cam and re-tune the MPI)

 

[Streffpilot]

Tell me more about cams and carb spacers..... please?

 

[Scott Danforth]

stock cam is a bit anemic. plenty of cams out there from either Crane, Crower or Comp as an off the shelf cam that will keep you on the good side of reversion (too much cam in a boat is bad). any time you change cams, you need to know the limits of your other hardware. stock vortec heads need to be modified for any lift over .420"

for a comp camp, I would run an XM264HR with stamped 1.52:1 roller tipped rockers on a set of vortec heads that have been converted to screw-in studs and have the valve spring pockets cut appropriately http://www.compperformancegroupstor...CC&Product_Code=12-416-8&Category_Code=RFHRXM

as for a carb spacer, any time you increase the intake plenum volume, you increase low/mid range torque. a 2" spacer helps the motor from 1500-3500 RPM and gives you a few extra ponies in this range. a phenolic spacer also isolates the carb from the heat of the motor.

a good quality high-rise marine manifold would have a similar effect such as the edelbrock RPM performer marine (dual alloy casting)

 

[FreeBeeTony]

as for a carb spacer, any time you increase the intake plenum volume, you increase low/mid range torque. a 2" spacer helps the motor from 1500-3500 RPM and gives you a few extra ponies in this range. a phenolic spacer also isolates the carb from the heat of the motor.

a good quality high-rise marine manifold would have a similar effect such as the edelbrock RPM performer marine (dual alloy casting)

So would a carb spacer make any difference if a high rise dual manifold is already in place?

 

[porscheguy]

What drive do you have? Built motors attached to alpha 1 drives are kind of pointless IMO, because what’s the point in having a high performance engine if you’ve always got to baby it along so you don’t trash your outdrive?

 

[Scott Danforth]

So would a carb spacer make any difference if a high rise dual manifold is already in place?

yes, it will help, however you may run into clearance issues with your hatch. I ran a 1" spacer on my small block with a high-rise