3.0 to 5.7 repower

[tumatuma]

Hello everybody.<br /><br />I just bought an old 76 16 ft lund for $500.<br />drove by it yesterday and it had a sign for $700.<br />The guy didn't know anything about it, he bought it last year. HE was gonna fix it but didnt. Did some DD and found out that the motor is not the iron duke (thought to myself when buying it, cause I have one in a junk fiero)<br /><br />Well got it home and first thing I did was put a battery in it to try turn it over. Spark plugs were already out. Starter ingages but it dosent turn over.<br /><br />Long story short, I pulled the head And found water in #3 and #4 cyl filled to top. Pistons in all cyl about half way up (or down).Very rusty. I'm sure the motor is frozen by rust. I dont see any cracks.<br /><br />Now heres the question. <br />I'm a stock car driver. Been racing for 10 years.<br />I want to go fast with this boat. Probally mostly down the river. It looks like I should be able to drop in a 350 that I have laying around. I've been wanting to do somthing like this for some time.<br /><br />The problems looks like...<br /><br />1. Getting new exhaust manifolds. Or why couldn't i just flip some old headers upside down and run this off the back. <br /><br />2. getting a new flywheel. The 5.7 motor is a one piece rear main seal. But with all of the small blocks out there, there must be a flywheel that'll bolt up and go. Where?<br /><br />3. getting throttle linkage to work with carb. Probbally use a stock 4 bbl quadgajet. Again must be linkage somewhere?<br /><br />4. maybe a new thermostat housing? Or I could rig the stock one to work? (If I use headers) <br /><br />5. Front motor mount. There must be one out there that will work with all of the 5.0 and 5.7's out there. Where do I get one. If I have to, I will fabricate my own.<br /><br />Dont tell me it cant be done. If I just stopped doing what I was doing because someone said "thats too much work" or "it cant be done", I'd be "working for the man" ( I've been self employed since 94). <br /><br />I've always wanted a boat kind of like you see on TV where the two ppl are racing little 12 ft'ers going through a maze to get the best time.<br /><br />I think I have the start of a cool "custom" boat.<br /><br />Any advice please? where to get parts? <br /><br />P.S. I've never owned a boat before, and I consider myself a hell of a mechanic.

 

[vipzach]

Re: 3.0 to 5.7 repower

This will be one hell of a project, I won't say it can't be done...just alot of work. What brand of motor/drive is it? Chances are you will need a different outdrive and have to redo the transom. I am sure it can be done. You also need to use marine grade parts, not just the stuff you get for a car. Safety issues there.

 

[tommays]

Re: 3.0 to 5.7 repower

its going to be to need more MARINE things than you may want to buy<br /><br />problem is the 4 cylinder drive has the worng final gear ratio for a V-8 2 to 1 should be 1.5 to 1 <br /><br />it would be hard to believe theres not problems with the lund hull that need to corrected <br /><br />most people do it the cheepest buy finding and old boat that allready has a power package they like and working from there<br /><br />its much harder to get the bits and pieces of a boat drive to fit toghter and FIT in the boat than a car<br /><br />tommays

 

[Limited-Time]

Re: 3.0 to 5.7 repower

First off welcome to iboats. Regarding your need for speed....how fast is fast in your mind? Having built a legit 90+ MPH go faster I can tell you that hull design will play a huge part in your quest for speed. If that Lund is a deep V you will have your work cut out for you. Speed on the water is not nearly as cheep as speed on land.

 

[tumatuma]

Re: 3.0 to 5.7 repower

Thanks for the welcoming.<br /><br />I just pulled the motor out. not too hard. It started to rain so I'm taking a break. I was about to pull off the flywheel from the 4 cyl to see how much different the bolt pattern for the flywheel.<br /><br />I just want to be faster than most boats out there. I have friends that go boating, I'm usually racing on weekends. I just want to be faster and louder than them. <br /><br />I dont know the differance from a deep hull or shallow. Well I guess I know the differance, Just dont know what I have. It's a sporty looking boat. Maybe shallow?<br /><br />I have to belive that the drive will bolt right up, with the proper flywheel. The bolt pattern for the bellhousing is identicle. <br /><br />4500 engine rpm with 1.5 ratio is 6750 prop speed<br />4500 engine rpm with 2.0 ratio is 9000 prop speed<br />If I'm doing it right, the 4 cyl ratio will be faster?<br /><br />Please tell me what marine grade parts I will need. Are you talking about the exhaust manifolds?<br /><br />I'm just playing and learning. Have alot of race car stuff lying around.<br /><br />Anybody done this before?

 

[RubberFrog]

Re: 3.0 to 5.7 repower

You'll blow apart the outdrive with the wrong ratio. Boats aren't as simple as cars. I'm sure you can find a flywheel somewhere, but you're going to need to replace/regear that outdrive. Imagine installing a v8 with the transmission out of a ford focus. How long do you think the tranny will hold up? Same difference.

 

[tommays]

Re: 3.0 to 5.7 repower

thery are all reductions 2:1 meaning the prop is running at hafe the motor speed<br /><br />there is no standard outdrive that can run above 5000 rpm at the input shaft<br /><br />pretty much everything is built around the 5000 rpm limit<br /><br />marine motors go fast by makeing a lot of torque BELOWE 5000 rpm to spin a BIG prop <br /><br />you have to forget things that work in cars <br /><br />and if you race cars boats also have a pretty tight set of saftey rules that keep you from becomeing a fire ball<br /><br />tommays

 

[mikebc]

Re: 3.0 to 5.7 repower

Tumatuma,<br /> I think most of the marine issues have to do with fire safety. Most of those are specific to ventilation. I too am mechanicaly incluned automotivly, not marine! I think a really good solution would be to connect one blower directly to the ignition, this would eliminate 1/2 the need for such concerns. The other remaining issues are with heat, like a plastic fuel filter just can't be a good idea in a enclosed cab that has a motor in it! Most important is common sense, I think too many members here have seen the "fireball" because someone was just stupid. Not all problems are from stupidity, but I'm willing to bet 90% or more are! Listen to the folks here and think twice about heat, venting, and fire safety and that with some common sense should keep you from a flamming fireball! Good luck on the retrofit, something I considered, but ended up just buying a faster boat! It was much easier!!

 

[Bondo]

Re: 3.0 to 5.7 repower

I can relate to your desires,.........<br />But You're starting with the Wrong boat,.. With the Wrong Driveline................<br /><br />That old stringer drive will Never take the loads You're talking about.......And it's Not Up-gradeable.............<br /><br />You've got the outdrive Ratios Backwards,...... It's a gear Reduction ,.......2.0/1 is 2250 Prop rpms to 4500 Engine rpms............<br /><br />There's ALOT more to Hull Design than Deep "V"s,+ Flat Bottoms,....... That old Lund is Never going to be a "Fast Boat",..... Except when compared to Other Old Lunds................<br /><br />Converting the Flywheel is a Minor Issue that can usually be gotten around,............<br />Except when dealing with "Old Stringer Drives"................<br /><br />And,.......<br />Lastly,.......<br />Dry Stacks are Only for Raceboats,+ Even Then,... Dry Stacks are Not Used............<br />You'll Have to use Wet Exhaust pipes/manifolds................<br /><br />I'm Not saying it Can't be Done,..........<br />But,<br />I Am saying it Could be ALOT Easier............<br /><br />Good Luck...