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Mercruiser 5.7 260hp

C

cvx16cvx

Member
I have a 1987 enchnater with a Merc 260hp 5.7 I/O. Boat runs great up to 4800rpm with a 23' mirage I am at 65mph. With an Alpha 1.
I want to go 70 mph.. Was thinking of going with an Edelbrock RPM Performer set of aluminum heads with the macthing intake carb and cam .. All Edelbrock, also was going to upgrade the ignition to all MSD.
With a $2000 budget I plan on buying off Ebay used heads and intake. I will buy the carb new.
Has anyone done an upgrade to their 5.7 260hp motor.
I would love to turn 5500- 5800 rpm all day! Any suggestions???
Should I buy a complete 7.4. 454 set up?
I just bought a new NOS Alpha SS lower unit case. Thanks cvx16cvx
 
when you do your cam you should do the timing chain and rockers too. get a double roller timingchain, and get some roller rockers. as for the intake manifold i would suggest the edelbrock victor jr air gap with a edelbrock650. that should bive you a substantial gain and alot more torque at all rpms...especialy high rpms.
 
cvx, just an idea. you should try the land and sea set back kit. it's a bolt on kit that should put you where you want to be or maybe more without giving up you stock engine. my friend has a 22' baja with the same engine and runs 66mph gps. the land and sea kit gave 7mph and his fuel economy is great. boatman
 
i don't think that flat tappet engine is going to turn 5500 reliable. (all day long) it may if you convert it to a roller motor, but that can get expensive at the machine shop.. you may consider talking to your local merc dealer about a non current engine package.. you get the whole nine yards, engine , drive, shield , trim pump, and warranty to boot.. it'l be above your 2k limit.. but well worth it in the long run.
 
You don't have room for a big block in that thing.Also you mentioned that you bought an S/S lower unit.Not sure if that S/S lower will work with that upper. I had one and I believe the upper case was different too.An Alpha s/s would probably work great on that boat.All that engine work is great but without good exhaust you won't reap the full benifits of it.Your current exhaust(if it's stock) is only 3".Those risers are very restrictive.
 
I'm not to sure about them land n sea setback plates they look goofy and Mercury has a bulletin saying not to use these. I'm sure they work but what is the cost in the long run? Stick to old fashion Horsepower for top end results.
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The major components are there. When I built my 540, I took the exhaust, pulleys and accessories, p.s. and oil cooler, motor mounts and bellhousing from the 454. The rest is there including all the wiring. The motor has never been raw water cooled, always closed cooling. I am looking for about $4k for it.
 
whats that new merc package??? i think its a 383, and i think the hp #s are above 340.. i havn't read all the specs on it.. but our shop is getting one to install.. should be here this week.. its a stroked 350.. and when i see it, and install it.. i'll let you know.. its supposed to be one rocking lil engine..
 
nope its a 383.. says so right across the cowling.. the merc site has very little about it yet.. i'm not sure what the hp is.. its either 340 or 360.. we expect to recieve this engine early next week.. and it is a bravo package .. will keep you updated
 
okay I am going to stay with a small block! Also keep the alpha set up with adding the SS lower unit. I was thinking og today taking a LS1 motor and marine spec ing it out.
Should I just do up the 5.7 260hp I have.. Going with some headers and Aluminum heads intake and hot cam???
I want to keep it reasonably priced. Are the 496 engines big blocks?/ Thanks Chris
 
i would not go aluminum unless you are willing to go to fresh water cooling!!!


even lake water will ruin aluminum heads

i would go with better iron heads like dart

then 1.65 roller rockers you might make enough
horsepower to get over 70 without major work

maybe change cams while you have everything apart

you are already at 9.0 to one compression

good luck daren

i think you would be suprised at just the rocker arm change maybe try that before you spend the big bucks

daren
 
wow.. we went from a 2k budgett.. to way off the wall.. what do you want.. and how much you wanna spend..
 
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Okay so the budget has changed
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but I want to stay low$$ Small Block. Maybe I will go with some dart heads or rework mine. Will Aluminum heads really be ruined by pond water??
What about the intake??
I found a clean set of used Edelbrock Performer rpm heads 64cc with the same manifold. Should I go this route?? Should I buy a crat 383 450hp set up? I can get one under $5K.
Cmon give it to me straight plan on pulling the engine next month...Thanks Chris
 
chris..

the 383 is a small block.. same footprint.. and a nice package!!

daren... pm me if you'd like to see the pics..
 
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