Motor upgrade??

[Stupid Fast]

Currently my boat has a 4.3LX mercruiser. I need(want really bad) more power. The boat is a 1995 starcraft 1810SS bowrider. A 350 will fit. I figure that I can build a junkyard 350 to around 300 turn key horse for fairly cheep. I cant aford a new boat right now, so for a few years this seems to be my only option. Do you think this hull can handle the horsepower or am I asking for broken stringers, cracked transom ect...?
From what I understand the castings are the same for marine and automotive 350s. The freeze plugs, gaskets, carb, cam, and electronic stuff is different. Would the starter, alternator, water pump, oil pump ect. transfer from my 4.3? I think the part #'s are the same. give me your thoughts.
Thanks Eric
http://mediaservice.photoisland.com/auction/Jan/20021163175906209537849.jpg
Here is a picture of the hull.

[crmax]

I would think your hull would be fine, I would look for a used marine small block chevy, the misc parts will add up real fast

[hack job]

well the marine motor isnt too inortant what is is that you dont put too much power to the out drive if you do you could damage it and that will cost a pretty penny. but as for the parts i really dont know if they are interchageable. good luck with that. the only thing i would say is be sure that you get a a set of marine gaskets and check the tollarnces on your out drive. good luck.

[superdave013]

Ok, by the end of the season I bet he'll have a big supercharger sticking out of the engine cover. http://free.***boat.net/ubb/smile.gif
Really I think your boat will hold up fine. The outdrive will last ok if you drive it with some brains. My buddy has a very stout small block in front of an OMC 800 and it has lasted for a long time. He turns a 4 blade 22 pitch prop @ 7,200 RPM. He just doesn't do hard hole shots and stuff like that.

[Slick]

Keep in mind I don't know shit from Shinola. I assume you have an Alpha drive. That should do you well as long as (like $$Dave said) you don't cram the throttle forward from a dead stop or get airborne.
Another option to look at is many people building new boats will order the smallest bravo package available, scrap the small block and install a big block, yet keep the outdrive. A friend of mine got a sweet deal on a brand new Mercruiser 350 by just calling a couple of builders. I hope that's an idea that may help you.

[Stupid Fast]

My outdrive is an Alpha 1 with a 1.84 right hand gear. I have heard that these are good for around 300 horse. Mine is pretty tight and only has about 150-200 hours on it. The drive is why I came up with a 300 horse small block. Plus that would be a very mild build.
Ok, by the end of the season I bet he'll have a big supercharger sticking out of the engine cover.
Unless money starts coming out of my butt(Hey it could happen), There won't be any blowers this season. I probably will not even have the motor done before fall.
Now Next season there is no telling what my end up under the engine hatch.
A friend of mine got a sweet deal on a brand new Mercruiser 350 by just calling a couple of builders.
How "sweet"? That sounds like a good idea.
Thanks Eric

[Slick]

If I remember correctly it was actually on a new 6.2L. The deal was not made with the Mfr., but with the person building the boat. It was to the tune of $3,500 or very close to it.

[Seth Livzz]

It's my understanding that the Chevy 4.3l is basically a Chevy small block with the front 2 cylinders chopped off. Same bolt pattern, water pump, accessory drive, ignition, etc.
For the price of building a small block and buying the needed extras (the exhaust alone will cost a pretty penny) you could buy a supercharger kit for it.

[LIBERATOR]

If your only looking for 300 HP I would bet there are after market parts available for your 4.3 that would get you there for less than building a 350, you know, cam, intake, carb etc. If you realy want a 350 e-mail me and I can guide you along. I've done 3 for my current boat. Also, your drive should be fine. I'm running about 400 HP through an Alpha 1 for three years with no problems.
Good Luck, Dave

[Bondo]

Just a thought,... Yes the alpha will take the power, NO problem..BUT, you have the wrong gear-ratio,you could compensate w/larger pitch prop (several $100.)or regear it to the 1.5 ratio(several$100.)..if your "95"LX is about the same as my "98"LX,you can see a major difference with a reasonably small investment..pull the intake,+ exhaust manifolds,port match them both, while cleaning up the ports a bit.. then loose the "Y" pipe + go out the transom, instead of thru the prop..Now with a full tune-up,(plugs,cap,rotor,filters,timing,etc.)take it to the pond,+ try it out.. you'l probaly need to retune the carb a bit.. i had to drop a size on the lo-speed jets(which didn't make sence, but cleaned up the plugs at idle), and a bit of adjustment on the hi-speed side..now you've spent a couple hundred instead of thousands,+ you maybe surprized..JUST moving the exhaust out of the drive will help alot..

[Stupid Fast]

Thank you for the idea Seth Livzz and Bondo.
I have considered building the 4.3LX But have reservations. The thought of a 300 horse V-6 is kinda cool. There is something to be said about a "sleeper" motor. My biggest fear is reliability and idol problems. I can sell the 4.3 block for a pretty good penny.(Some people just need to bite the bullet and pay someone to winterize their blocks). Dollar per horse leads me to the 350. If I reuse the waterpump, timing hardware, starter, alternator, and even the carb(Carter 4 barrel) I should be able to get 300-350 horse for pretty cheep. Plus if I get a newer boat 400- 450 shouldnt be to far away with new heads ect.
Bondo- What kind of improvements are you suggesting 3-5mph, planing, or what. I am looking for 65-67mph (currently runs 52-56 depending on weather and water conditions.) 300 horse should get me there with my drive and a 26-28in prop at 5500 rpm.
Seth Livzz
I have not seen any supercharger kits for the 4.3 carbed motors but if any of you know who has one I would also like to investigate that route.
Thanks everybody
Eric

[Bondo]

I guess my point is;
With a Super Tuning of your Whole boat system, I Think you should be able to easily break 60mph, Maybe more.....Points; the weber 4bbl. is a pretty easy, simple,tunable carb., getting the exhaust out of the water is esentcial, to let it breath..the port matching is a big bang for the price of gaskets..What about your Prop ?? NO Matter how Much Power you make, the PROP is the Most Important part of the whole equation...I'm running a land&sea shifting prop, i love it...it starts at 11" pitch... if you Slam the throttle, the LX roars to 4400,+ stays there....And What about the Boat ??? back it up to the garage,+ throw out ALL the sh-t you didn't use the Last time you're out... I think???

[Stupid Fast]

Bondo
What type of boat do you have? How fast does it go? I have a friend who has a variable shift prop. He likes it but it can be tempermental.(only boogers up when he is showing off to the girls though). I like to ski.
http://mediaservice.photoisland.com/auction/Jan/20021165836280786049914.jpg
19inch high five prop
I also have a 21 and 22 inch stainless
I know that the 4.3 has potential. Most of the small block tricks will work, but 262 cubes is not 350 or 383 cubes. Cams are hard to come by, I have yet to find a forged crank, and after market headers(marine) just don't seem to exsist.
Has anyone built one?
Like I said I like to ski and go fast.
my current motor is just not cutting it.
To me it is worth more to sell the long bolck and build a 350.

[Stupid Fast]

P.S. Does anyone know weather the 1995 4.3lx has roller lifters or not? Even the shop manuel says two different things? Who knows the real answer befor I start yanking shit apart just to find out?!?(it really has been killing me not to know)

[Bondo]

Stupid Fast, i'm playing with a halfa deck,...well really, a 1974 22' starcraft Islander,fully equiped for lake Ontario Salmon+ Walleye charter type fishing...close to 5000lbs of fun...36gals. fuel, 3 people aboard, in a perfect 6" chop, 53mphgps.. in the salt....back here in sweetwater, same load,+ conditions, 43-44mphgps....LX turning 4450rpm, thru an alpha 1 w/1.5-1s, L&S prop tuned to about 18" total advance...i didn't care for the 140hp/4cyl. when i bought the boat 5yrs ago...i went from 28mph to 43.i've pounded the rivits out of my tin boat for 300hrs. in the last 2 seasons.....your friends prop, a good long Blast of wd40 every time you go back on the trailer will do wonders..gives ya a chance to pick the boogers out while thier still Wet !!!
i don't know what you have in mind, But, if you want a 5000+rpm rocket, your right, the 4.3 won't do it..you already have the Best cam grind for making torque(a lopy idle cam is Not what you need in a boat,maybe long ratio rockers?) so if your not turning over 5000rs, you don't need a forged crank...you could go with high-comp pistons, but is it worth it?? the best way out i see is, find a 350cid mercuiser takeout, running, cracked block, whatever...now you have all the STUFF..nuts,bolts,brackets,carb?,manifolds?, wiring,etc....now you salvage what you can from this, add a 383 stroker kit, + a "Truck"cam...don't get crazy with the cam grind,+ the forged vs nodular cranks....keep you compression down to about 9:1..now you've doubled your hp,+ your Torque....And you still have the LX to sell as a low hrs. running engine....NOW add the L%S prop,+ by your 3rd deepwater slalom start, you'll be able to scratch your ankles without bending over.....
i think you'll find the roller cam motors are the motors with the 3rd, or counterbalancer shaft(mine)...look at the top of the timing cover, behind the waterpump.. the motors in question have a big hicky in the top of the timing cover...don't look nothing like the sbc covers...