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New member with a 57 question

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flightmate

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"Hi, I have a 1996 5.7 with a

"Hi, I have a 1996 5.7 with a 2 barrel carb that puts out 210 h.p. I am thinking about putting on a 4 barrel and intake to help bump up the output a little. Looking for suggestions as to whether I should go with a stock 4 barrel and intake, or go aftermarket with one of the edelbrock units, or just leave it alone. Also what gains I could expect? Thanks in advance for the help. I have done some reasearch but have been unable to find anyone who has modified one of these engines to see how it responds."
 
"You'll spend about $1,500

"You'll spend about $1,500 for a Rochester carb, manifold and linkage bracket from Mercruiser. A number of members have recommended the Edelbrock carb and alumnimum manifold. A boat graveyard or eBay will have used parts if money is tight."
 
"You should gain about 20-25hp

"You should gain about 20-25hp with intake and 4 barrel. What size/type boat? I suspect you will gain 1-3 mph at wot. To give you an idea of how much power is required to move a boat thru the water: I recently repowered from a 1994 5.7 4 barrel rated at 235hp to a 300hp Mercruiser 350 magnum. I am now able to spin more prop and my 3400rpm speed went from 24mph to 32mph (65hp gained me 8mph). It does plane much more quickly and is not sluggish in choppy seas anymore. My economy improved from 2.25mpg to 3.4mpg also, so it will eventually pay for itself. I have a heavy 23' w/a 20 deg deep V."
 
"One more point: as long as yo

"One more point: as long as you are in the engine it would not be that difficult to take it up to about 300hp but would require engine removal. Camshaft, vortec heads, aluminum intake, and 4 barrel should get a very noticable performance increase."
 
"Thanks for the information.

"Thanks for the information. From what I have read it seems the only difference between your old engine and mine is the carb/intake, so 25 hp is probably a good guess. The boat is a 19 foot Sylvan open bow runabout. Maybe 2600 lbs full of fuel but without people. I haven't had it out on a smooth lake yet, but on the river the GPS showed 51 mph. The previous owner said it would do 55 before he put a hyrofoil on, and now does 52 or so. I was hoping to pick up maybe 5 mph, but that sounds like it might not be possible without the engine mods like you suggest. I am not very mechnaically inclined, so I was trying to stick to the easier mods out there. Congratulations on the new engine. Sounds like a gem. It is amazing that your mpg went up so significantly, along with the increased speed."
 
"I suspect the 1994 hp was sig

"I suspect the 1994 hp was significantly down from 235hp. The engine did not seem to burn oil but did have blowby (smoked from valve cover vents). Using the same prop economy went from 2.25mpg to 3mpg so the new engine is definately putting the fuel to better use. The biggest gain I believe comes from the added torque the vortec engine produces and thus being able to go from a 15" pitch prop to a 18". I would remove that hydrofoil, it must be dragging. Your size/weight boat with a 350 V-8 should have no problem getting on plane which is what the fin is supposed to help."
 
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