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  #31 (permalink)  
Old 08-29-2013, 10:19 AM
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Quote:
Originally Posted by OLNOLAN View Post
I have given thought to a small blower, it would make some nice power right where you need it.

However, I've tryed to remain conservative with my lil Alpha 1.

I spent boatloads of money(pun intended)on an old piece of junk OMC 800, blew it up countless times. I finally did a total transom rebuild and converted mine to the Mercruiser Alpha 1.

A little history on the Alpha drive; Mercruiser ran this drive with different power plants up to a 365 hp 454. When the warranty work started costing them alot of money they realized they had pretty much found the HP/Torque limitations of the Alpha with the BBC. Thats when the Bravo was born, built to take the brutal torque of the BBC.

I wish I could have afforded a Bravo drive for my boat, but at the time a complete Bravo was more than double the cost of an Alpha. I've got a 502 Mercruiser I could drop in it now but it would likely twist the Alpha into a pretzel.

Without giving away all my secrets, the best way to build a high performance engine for a stern drive is too; 1)realize the torque limitations of the outdrive. 2) Try to utilize engine components around achieving the most torque and horsepower you can get on the chart @ 5250 where the two cross. If you have to make a compromise between the two, always go with the package that makes the most torque in that 5000 rpm window. Nolan
This is essentially real good advice for the most part.
The engines I built for this all had a ton of torque. Actually more torque than
the prop could use all at once. (prop cavitation)
If you tried to rug it wide open from a stop.
But if you found the sweet spot that allows you to give it just the right rate of throttle it would literally jump right out of the water, up on plane.
Cams in the 218 to 226@.050" range work real well.
What works the best overall on these builds is well known.
The single 355 w the 142 blower was a Alpha 1 in a Scorpion.

The twin full race methanol fuel 6700+ rpm 500hp 355's boat had the Alpha II drives.
The race engines (w big Isky flat tappet race cams) were suprisingly reliable.
Was definally pushing the Alpha Drive to the max. And then some.
Thats why Merc Racing has a whole line of Racing Drives.

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Last edited by F-BIRD'88; 08-29-2013 at 10:29 AM.
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Old 08-29-2013, 12:42 PM
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sorry guys I'm still here. for some reason I'm not getting emails telling me sometime has replied. I'm at work right now but will definitely reply tonight. you guys are amazing,I am very happy to have all the help.
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  #33 (permalink)  
Old 08-29-2013, 01:40 PM
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Here is another thng you can consider doing.
Build a low cr supercharged 305 with the 142 weiand blower.
Get the cr down to 7.5:1 on the 305, get the head flow up (home ported 350 vortec heads or something good liek that0 The low cr allows you to run a good bit of Boost yet not have to retard the timing so much under boost. This keeps the exhaust valves cool. The 142 blower does not need to run so hard ot make the boost on a small 305 cid engine. SO its running efficiently. (read that cooler blower discharge air temps)
cooler is better.
The blown 305 will go like no 305 you ever seen.
There are other heads you can use besides vortecs on the 305.
If you are stuck with a 1.65:1 drive this is a good way to go fast with that drive ratio.
Its different. The 305 build is straight forward simple. dished 305 replacement pistons.
larger chamber heads the larger the chamber the better. But the ports got to flow air.
( stock 305 heads won;t make any power. and the chamber is too small)
Avoid crappy heads like the 882's or 462624's.
A S/R head with 1.94x 1.50 vales and large 76cc chambers that you have ported yourself
will work very good. A 441 or a 920 head is goood for this.
Uses pretty much the same blower friendly camshaft ( hyd flat tappet or hyd roller)
The blown 305 will make very good power in your boat. The 142 blower is very efficient on a 300+/- CID high perf engine.
Use a 750+cfm carb and magnum manifold/thru the hull exhaust just like the 350 combos.

I have a solid lifter cam version of this supercharged motor too.. It will rev like you never seen.
But the cam is "streetable" and "marine friendly". good with the 1.65 drive ratio.
Can you see running flat out at near 7000 rpm with a blown 305 from hell..
Your wifeey will be cussing and cursing my name all the way across the lake till you get off the throttle.
She will not believe that its a "305".

it will also cruise at 5000 rpm real nice. It just that when you open it up the lil blown solid lifter 305 is going to rev.
You can build this motor yourself. It is not a hard motor to build at all.

you dial the horsepower up and down with the blower boost/pulley swap and the prop choice and fuel octane choice just like my blown 355 combo.

you will have no problem pulling multiple tubers with this supercharged 305. It makes great torque and power.

At least if you do happen to smoke your Alpha drive you will have had a ton of fun and gone ripping fast,, doing it.

Last edited by F-BIRD'88; 08-29-2013 at 02:04 PM.
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  #34 (permalink)  
Old 08-29-2013, 02:17 PM
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Add water methanol injection will allow you to crank the boost and timing up and run "Flat out"
Without killing it. you will slay your fair share of Big blocks out on the lake with this lil blown 305.

So can your wife hold a radar gun , read the tach and scream my name at the same time ?

Last edited by F-BIRD'88; 08-29-2013 at 02:22 PM.
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  #35 (permalink)  
Old 08-29-2013, 03:10 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
Add water methanol injection will allow you to crank the boost and timing up and run "Flat out"
Without killing it. you will slay your fair share of Big blocks out on the lake with this lil blown 305.

So can your wife hold a radar gun , read the tach and scream my name at the same time ?
how much would a build like this cost?
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  #36 (permalink)  
Old 08-29-2013, 03:34 PM
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can you rebuild a SBC your self.
Basic 305 rebuild kit, dished pistons. rings bearings gaskets
The build is very straight forward.
You need to get the block bored and honed and the crank turned and the rods resized.
The 350 Vortec heads need a bit of home prep.
All engine parts are off the shelf items for this motor.
marine friendly brass frost plugs are nice.
you want to build it a little loose. its a marine motor and it will rev.
+.001 .002" piston to wall
add 40% to the piston ring end gap. you want Generous piston ring end gaps.
straight forward bearing clearances .002 rod .0025 mains.
There is nothing fancy about this build. There are no fancy parts

its up to you if you want to build the hyd cam sissy version or the "premimum" take no prisoners street solid lifter version
The cost is exactly the same. This version can just rev higher and will.
You get as machinist to machine the block,crank and rods and take it home wash it and assemble it and paint it.
You can even get the mahine shop to assemble the short block for you.
They just got to understand the required build clearances for running boost on this motor.

The fuel system on your boat will need a upgrade for more fuel flow capacity. This ain't no wimp motor.
You want to keep the fuel system marine safe thou. Its a matter of parts selection.
All are off the shelf stuff.

Do you have the Merc Magnum ex manifolds and thru the hull exhaust?
Often its a good idea to replace the exhaust manifolds when you rebuild the motor.
some times they are cracked or rusted out inside . They don;t last foreever
New ones are not expensive.
You want to service the water pump in your drive too. Make sure the gimble bearing and the coupler is good to.
Check the drive for gear back lash. basic stuff that needs to be checked anyway.

You need a marine 750+ cfm carb Double pumper is best. Edelbrock is ok.
The Mercruser Qjet will work with modes and upgrades.
The 142 blower kit is about $2500
new GM 062 vortec heads with a few up grades. and home tweeks to get them ready.
valve springs.

Last edited by F-BIRD'88; 08-29-2013 at 04:01 PM.
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  #37 (permalink)  
Old 08-29-2013, 04:06 PM
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what other SBC 350 cylinder heads do you got there to work with? 1.94 valves is prefered for this 305 build.
casting numbers.

Vortec heads is just one (good) way among others to skin this cat.
The New small port BOWTIE Vortecs are bolt on ready and will build a SERIOUS Blown 305
with the weiand 142 blower kit (vortec)

Last edited by F-BIRD'88; 08-29-2013 at 04:12 PM.
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  #38 (permalink)  
Old 08-29-2013, 04:53 PM
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The stock Merc Thunderbolt ignition won;t work for this.
It won;t let the 305 rev up high enough.
Most people ditch it and go to a high quaility marine ready HEI distributor.
You want to add a boost retard box to it. The mechanical advance curve needs to be modifed
but its simple to do.

You must use Marine cert marine comparable parts on the ignition and fuel system.
Pretty much any 750 800 850 carb will work with a few mods but a holley 750++ DP is best.
Must be marine comparable too.
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Old 08-29-2013, 08:45 PM
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the blower build definitely is interesting. maybe I'll make my way to Canada after retirement and hire your for a consultant during the build . but for now I think we are going to go with a regular engine. I did some looking at the drive today and I seen it has 1.65 stamped on it. I hope this won't be a lost cause or a deal breaker. I am interested in some advice about building the engine to use this drive. but also, Is it expensive to change the gear ratio to a preferred/ better ratio?
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Old 08-30-2013, 04:45 AM
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When you find out the real price of a new Merc Alpha II 1.50:1 Outdrive the beauti of this will become more apparant.
If your boat does not have thru the hull exhaust don't expect much from a high performance engine.
You will need power drive trim too.
When you get it wide open and all trimmed up only about 6" of the back of the boat's hull will be in the water at all
@ speed.
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  #41 (permalink)  
Old 08-30-2013, 06:15 AM
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Quote:
Originally Posted by F-BIRD'88 View Post

When you get it wide open and all trimmed up only about 6" of the back of the boat's hull will be in the water at all
@ speed.

And if you are lucky, you wont encounter the "fun" (terror?) of chine walking at 60 mph with many You Tube vids showing that experience.
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  #42 (permalink)  
Old 08-30-2013, 10:13 AM
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Originally Posted by Richiehd View Post
Bob, Give Mike Jones a call at Jones Cam Design. He is very knowledgable and familiar with boat engines. He does cams for many different applications including Jersey Skiffs, Cracker boxes and Hot Rods. He knows what "water reversion" is unlike the tech guy I spoke with at Comp Cams.
He will hook you up.
Richie
watch what cam you have or put in there. seems reversion is only a factor to the boat owner not the cam company. i mean that. reversion could hydrolock the engine, worst case blow a rod through the block or light case scenario it will rust your exhaust valve and seats and compression will be down after a couple seasons. also chine walking is very dangerous and overpowering a boat is the one way to get you ejected from your boat. usually whene you get ejected, unless you have a tether cord your boat will turn hard around and go in tight circles at whatever speed you were at at the time of ejection, around where your floating in the water. that would be some pretty scary stuff. i see your wife is leaning tward a new engine but you cant buy a "good" choice built 305 engine in a crate. just stockers. but a 305 can make good torque if you build it with flattops .040 over pistons and vortec l31 heads. or even 081's would work well and you wouldnt have to buy an intake to match the heads. your q-jet would need a little tuning but your ignition will work great and drive ratio would be fine. that will save you some money and get you going a good bit better than the old power plant. i love a 305 and have relied on em for years glad to hear you wouldnt mind keeping a 305. i recomend you go .040 over and make it a 311 but either way a 305 is good. wont set the world on fire but there small displacement and high torque is a appreciated at the pump and they are super super reliable probably because they dont run as "hard" as other engines. if you have the old log style exhast then throw them in the scrap pile and get some newer header style upright manifolds from the late 80's early 90's alphas. they work very well on a 305 even through the prop. the prop while spinning, actually pulls exhaust from the engine like a vacume so once rpms are established thru-hull exhaust doesnt do anything for a 305 compared to thru-prop. its those crappy log manifolds holding the exhaust back. loose em.

Last edited by s-10again!; 08-30-2013 at 10:33 AM.
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  #43 (permalink)  
Old 08-30-2013, 08:57 PM
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Originally Posted by BobBoat View Post
the blower build definitely is interesting. maybe I'll make my way to Canada after retirement and hire your for a consultant during the build . but for now I think we are going to go with a regular engine. I did some looking at the drive today and I seen it has 1.65 stamped on it. I hope this won't be a lost cause or a deal breaker. I am interested in some advice about building the engine to use this drive. but also, Is it expensive to change the gear ratio to a preferred/ better ratio?
I can agree with everybody about how much fun a blown boat can be,, but they can and WILL be very expensive if you think you have to have that throttle on the floor too much
I had a 18 Ft Pantera jet with a Blown 383 small block chev, and 2 other motors , (all 3 were blown latterly),,,,all within a 3 year period,, pretty expensive boating,, but on the other hand,, you don't have to run them full bore all the time,, its just so much fun to go fast,
I no longer have a boat,,,

Bill
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  #44 (permalink)  
Old 09-01-2013, 06:26 AM
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Here is a example of a 305 that has been hot rodded with vortec heads
and a hi perf camshaft. You can see that when hot rodded even with this relatively modrate duration 224/230 cam a 305 engine wants to rev up to make power.
Could you imagine this motor with a 142 blower?
The hyd cam as already starting to give up the ghost at just over 6000 rpm
Thus the need for a mechanical cam to extract the max power from these motors
They like to rev up. Especially with a blower.
305 Chevy Engine Blocks - Engine Masters Magazine

While you would want to cruise at between 3000 and 5000rpm in a boat.
Short WOT blasts to 6000+ rpm to obtain maximum horsepower and top boat speed are fine.
The 1.65:1 drive ratio should not be a problem. proper prop selection is critical.
A slightly different wider 112 to 114 LSA version of this cam will be more marine wet exhaust friendly.
Such as Crane H278-2 (HMV-278-2) 113801
Hot rodded 305's like to and need to rev up to go fast.

Last edited by F-BIRD'88; 09-01-2013 at 06:32 AM.
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Old 09-02-2013, 09:37 PM
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I just happened to be talking to a co worker Friday and I was talking to him about my boat. When I told him that I'd really like to get a Vortec engine and rebuild it he said his brother was talking about scrapping his 98 Chevy 1500. So he called his brother and just so happens he still had the truck. His brother told him it is a vortec 350 with 250,000 miles. After work I went over to his brothers house and looked at everything. Didn't hear the engine run but he said it ran fine when he parked it but it's been sitting for a few years. So for two hundred bucks,I pull the engine then haul the truck to the scrap yard for him the engine is mine.

I plan on a total engine rebuild. So I am building a vortec 350 for the boat. Would still like suggestions on building this engine now that we know for sure of the size.
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