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Topic Review (Newest First)
02-23-2013 09:05 AM
bondo
Quote:
Originally Posted by F-BIRD'88 View Post
Quote:
Originally Posted by crussell85
Is this a bad out drive?
I'm not real up on this Penta drives. I am of the opinion they are light duty.
This hi perf 383 motor build recipe I laid out is no wimp.

Hot rodding a boat is not the same as hot rodding a car.
It is never cheap.

A Mercruiser Alpha drive (V8 {1.5:1 ratio} in good condition is the minimum.
Mercruiser will tell you you need a Bravo Drive for this engine.

Any all V6 engine drives will not work.
The stock default thru the drive exhaust routing will not work.
Ayuh,.... I believe you'll find that the SX drives are cone-clutch drives, which are miles ahead of the Merc Alpha drives, more like the Bravos, but not quite as heavy duty...

It's a dependable drive up to 300 hp, 'n still dependable over that, if the operator has self-control over his righthand...
in other words, skip the WOT jackrabbit starts, 'n yank back on the throttle if by chance ya clear the water, 'n catch air on a wave...

'n,... The thru-prop ain't so much the problem, but the open plenum exhaust manifods are the choke point in the exhaust flows...
The vortex created by the prop, actually helps pull the gases out...

Quote:
Originally Posted by F-BIRD'88 View Post
If the SX drive on your boat is not in excellent condition do not hot rod the engine.
A worn drive will not last behind a powerfull engine. A 4 cyl V6 drive or drive for a 305 is light duty and usually the wrong internal ratio.

If this is a light duty drive just enjoy your boat for what it is.
Or it will soon become a lawn/driveway ornament.
Only the Ratio changes, each drive is as strong as it's sisters....

'n, of course, a Worn out drive isn't dependable, regardless the amount of power applied...

There's No reason the OP shouldn't move forward with his Plan,...
383s are stuffed into boats, quite regularly...

If crussel would like a more Marine rated conversation 'bout this,...
Feel free to stop by iboats boatin' forums,...
There's many conversations there, 'bout this exact thing...
02-22-2013 05:43 PM
troutman2 We still build that 5.7 engine w/ the same intake as the mercruiser in which is a Bosch injection set-up.
02-22-2013 07:40 AM
lg1969 Hey BadBehavior, That boat is sexy like a good women.
02-21-2013 03:15 PM
BadBehavior
Quote:
Originally Posted by F-BIRD'88 View Post
If you wnt to go fast and have fun on the water find a good used Hydrostream.
Google it.
Been reading this Post. I agree with F-Bird on all, Except this, to each his own of course, GO fast, Get one of these, put 6 cyl in present boat, sell it put funds into safer boat than the above "chine walker" I know, I owned 2 before I wised up! Sorry had to say it
Larry
02-21-2013 11:44 AM
Hogg Here is the Ramjet intake for Vortec heads.


Merc marine intake for Vortec head use. Used on 305/350/383 marine engines, I run this in my 1997 Vortec 350 reg cab shortbox 2wd truck, runs much better than teh stock truck intake, and allows me to run any sized injector I wish(unlike teh stock truck intake)


Same marine intake next to Vortec truck intake manifold


Same intake in Mercruiser red



different angle


Here is the same marine intake with the upperplenum removed. You can see how the runner eopenings are across from the cylinder head intake port it feeeds. the cross ram runners are about 10" long from the opening inside teh plenum to the intake gasket flange.


Inside of Vortec 305/350 truck intake. Lots of injection debris impeding flow.


Scorpion 400 intake, it uses the same tunnel ram lower that is mentioned elsewhere in this thread.



peace
PAuly
02-19-2013 05:14 PM
Richiehd
Quote:
Originally Posted by crussell85 View Post
So... ... maybe just look into the 7395 cam and the stock vortec heads?
In my opinion that 7395 has too much duration for wet exhaust. You may end up with water reversion, and a no start in the water.you need to pick a marine performance cam or speak to someone that knows marine camshaft design. (Mike Jones Cam design, Denver NC)
02-19-2013 01:30 PM
F-BIRD'88 If you wnt to go fast and have fun on the water find a good used Hydrostream.
Google it.
02-19-2013 01:10 PM
crussell85 So... ... maybe just look into the 7395 cam and the stock vortec heads?
02-19-2013 01:03 PM
F-BIRD'88 Do you know how to make a boater into a Millionaire?

Find a Billionaire and give him a power boat, and wait...
02-19-2013 12:03 PM
TMF Lindbeck There are many calculators on the Internet to figure your hull speed and the hp required to go a given speed in knots I would google for a hull speed calculator. I've found on my 16 ton 42" dive boat the first 7 knots ill need 60 odd hp but if I would want to go a additional 4 knots at 10 kt ill need a additional 400 hp. My leingth at the waterline and tonnage Re holding me back. For your little 20 ft'er you can really get going with little hp but you'll find a point whare it takes more than 100 extra hp to just gain a knot or 2. Basically what I'm saying is you can build a 350 hp engine and get a max speed of 8.5 knots or a 900 engine and go 12 knots in my case. What would be the better bang for the buck? Easy choice for me was a cat 3208 as opposed to a MAN with triple he hp and only going marginally faster
02-19-2013 10:57 AM
F-BIRD'88 If the SX drive on your boat is not in excellent condition do not hot rod the engine.
A worn drive will not last behind a powerfull engine. A 4 cyl V6 drive or drive for a 305 is light duty and usually the wrong internal ratio.

If this is a light duty drive just enjoy your boat for what it is.
Or it will soon become a lawn/driveway ornament.
02-19-2013 10:37 AM
F-BIRD'88
Quote:
Originally Posted by crussell85 View Post
Is this a bad out drive?
I'm not real up on this Penta drives. I am of the opinion they are light duty.
This hi perf 383 motor build recipe I laid out is no wimp.

Hot rodding a boat is not the same as hot rodding a car.
It is never cheap.

A Mercruiser Alpha drive (V8 {1.5:1 ratio} in good condition is the minimum.
Mercruiser will tell you you need a Bravo Drive for this engine.

Any all V6 engine drives will not work.
The stock default thru the drive exhaust routing will not work.
02-19-2013 10:24 AM
crussell85 Is this a bad out drive?
02-19-2013 10:22 AM
F-BIRD'88
Quote:
Originally Posted by crussell85 View Post
Its a 2001 Volvo penta with the sx out drive.
sorry about your luck.
You need a 1.5:1 ratio drive that can take some power.
Not real sure how a SX drive will stand up. The thru the drive exhaust will kill the power any way.
This is a high perf motor. Needs a hi perf drive and exhaust system (thru the hull or silent choice or Marine water jacketed headers)
02-19-2013 10:18 AM
crussell85 Its a 2001 Volvo penta with the sx out drive.
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