LSx into Jet Boat??
You bring up a good question, how do you turbo a setup that's flowing water through the exhaust? Being heat will be an issue I'm thinking about using the procharger and a water to air intercooler. Don't think I want all the turbo heat in mine. Thinking about putting ac on it too for the cabin 
Mercs new hi performance motors are turbocharged. Years ago there were a few carbed turbo big blocks available too, they had reliability issues though.
They use a water cooled dry manifold and water cooled turbos. It's a stainless housing welded around the turbo hot side, you can find these on ebay sometimes.
As for cams, marine and turbo cams have some things in common. Wide LSA to prevent reversion with marine and prevent the boost from blowing through with a turbo. I'm not much of an expert with turbos, but for a 5.3 I would think an LS1 or LS6 cam would be a economical solution.
They use a water cooled dry manifold and water cooled turbos. It's a stainless housing welded around the turbo hot side, you can find these on ebay sometimes.
As for cams, marine and turbo cams have some things in common. Wide LSA to prevent reversion with marine and prevent the boost from blowing through with a turbo. I'm not much of an expert with turbos, but for a 5.3 I would think an LS1 or LS6 cam would be a economical solution.
You bring up a good question, how do you turbo a setup that's flowing water through the exhaust? Being heat will be an issue I'm thinking about using the procharger and a water to air intercooler. Don't think I want all the turbo heat in mine. Thinking about putting ac on it too for the cabin
Teching In
Joined: Dec 2010
Posts: 42
Likes: 0
From: Way North in CALI
You bring up a good question, how do you turbo a setup that's flowing water through the exhaust? Being heat will be an issue I'm thinking about using the procharger and a water to air intercooler. Don't think I want all the turbo heat in mine. Thinking about putting ac on it too for the cabin
a water line runs from the manifolds to the riser and water flows out the riserinto the exhaust
The way i have it planned is to take away the riser, and make new non cooled risers (leaving the water jacketed manifolds) that would merge into the turbo flange,.. Then from the turbo, i might just run a pipe over transom, or split it back into two and exit through transom, if i do the later i would want to re add water down stream after the turbo
So the cooled manifold would lower exhaust temps, but i wouldnt have water flowing through the turbo.
At least thats my plan.
lol
So you think i would be good with just a LS6 cam,
can those springs handle somthing like this
or would either of these be better over the ls6 or would the ls6
do better ?
Duration at 050 inch Lift 224 int./228 exh.
Advertised Duration 273 int./278 exh.
Valve Lift with Factory Rocker Arm Ratio 0.591 int./0.600 exh.
Lobe Separation (degrees) 113
or
Duration at 050 inch Lift 226 int./232 exh.
Advertised Duration 281 int./284 exh.
Valve Lift with Factory Rocker Arm Ratio 0.578 int./0.587 exh.
Lobe Separation (degrees) 115
THanks
Teching In
Joined: Dec 2010
Posts: 42
Likes: 0
From: Way North in CALI
Also looking at this Cam kinda Close to the LS6 cam with some differences
Duration at 050 inch Lift 216 int./220 exh.
Advertised Duration 283 int./286 exh.
Valve Lift with Factory Rocker Arm Ratio 0.560 int./0.560 exh.
Lobe Separation (degrees) 114
Duration at 050 inch Lift 216 int./220 exh.
Advertised Duration 283 int./286 exh.
Valve Lift with Factory Rocker Arm Ratio 0.560 int./0.560 exh.
Lobe Separation (degrees) 114
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Registered User
Joined: Apr 2014
Posts: 1
Likes: 0
Ls1 in scarab jet I have a complete Ls1 minus ECM an wiring. Wanting to put in my scarab jet boat. I found exhaust manifolds I think will work ( read that coils might be in way )
Just about everyone tells me to just do the edelbrock carb conversion and be done with it. I would like to get a aftermarket or used ECM an wires if possible. Nobody local knows how to program this setup for marine
QUESTION:
1) Is it feasible to go ECM route? If so what are my parts and how much?
2) What are steps to take?
3) Is there anyone that will flash / / sell comp for me and make a simple harness. I am using wet exhaust so I don't think I will have O2's ( is this right?)
4) what cam would be good for this marine setup?
5) what fuel pump? Got existing that came off my old vortec setup. Will this work?
Just about everyone tells me to just do the edelbrock carb conversion and be done with it. I would like to get a aftermarket or used ECM an wires if possible. Nobody local knows how to program this setup for marine
QUESTION:
1) Is it feasible to go ECM route? If so what are my parts and how much?
2) What are steps to take?
3) Is there anyone that will flash / / sell comp for me and make a simple harness. I am using wet exhaust so I don't think I will have O2's ( is this right?)
4) what cam would be good for this marine setup?
5) what fuel pump? Got existing that came off my old vortec setup. Will this work?
Registered User
Joined: Feb 2019
Posts: 1
Likes: 0
From: Alberta
Exhaust manifolds. 
Not sure if anyone in the US is making a log manifold for LS motors, but could be this:
https://www.tawcomarineproducts.com.au/ls1-manifolds/
Alternatively, Ford 351 Cleveland marine log manifolds are adaptable to LS heads.
https://www.tawcomarineproducts.com.au/ls1-manifolds/
Alternatively, Ford 351 Cleveland marine log manifolds are adaptable to LS heads.
Registered User
Joined: Feb 2019
Posts: 1
Likes: 0
LS swapped Jet boat guys Im trying to figure out the water plumbing on an LS 5.3 engine that Im swapping into the Jet boat. Anybody have any detailed pictures of your raw sea water cooling system with wet headers?
On The Tree
Joined: Sep 2011
Posts: 179
Likes: 0
From: fredericksburg va
it has no way to change the impeller since its a jet boat, you might want to have the pump checked out i have a buddy that just got his jet boat done but they are ford people its got a like a stroked 460 and they had there pump build and his boat will run in the 90s
