4 BBl Carb and Intake for 5.0 Mercruiser

[Riley]

Hey Guys, I recently purchased a new 1999 18' Classic. I love the boat, but have quickly tired of the sick little 305 2 bbl. Any suggestions for an intake manifold and carb? I believe this engine has the Vortec heads, which limits my choices. I'm looking to pick up a few mph this summer, with the intention of throwing in a hot crate motor over the winter.

One other question: I've been told the Alpha outdrive is only good for 300 h.p. and 5000 rpm. Is there any way to beef this unit up to withstand more horsepower? I'd like to get the boat to run in the 65+ mph range, which I'm sure is gonna require more than 300 hp! Any suggestions or ideas would be greatly appreciated!

Thanks,

Chris

[PaulO]

Riley,
I don't know how much help a 4bbl conversion will do with the 305 but, I believe Edelbrock makes a performer manifold for the vortech motors. That along with the edelbrock marine carb would probably work well out of the box. If you are going to do a crate motor over the winter and plan on utilizing a vortech motor, you may be looking for an Edelbrock performer RPM manifold instead depending on what the build will be on the crate motor. You may want to buy now and then swap the manifold/carb onto the new motor when ready.

As far as the Alpha drive goes, I am in the same boat ( literally as well as figuratively). My crate motor will be making somehwere between 380 and 400 HP and that will be pushing the poor Alpha. I have not seen any upgrade parts available for strenghening the Alpha. I have noted that most of the Aplha failures I have heard about are of the upper gearcase. To help prevent this, I have installed a multiport drive shower. I am fairly easy on outdrives since I always apply power gradually rather than mash the trottle. I will continue to do this with even more care and, if the Alpah goes, do either an Alpha SS or a Bravo upgrade.

PaulO

[RickSE]

Riley,
I went through this early this summer, but with a 350. Check out these posts, they may help.
http://www.donzi.net/ubb/Forum1/HTML/000160.html
http://www.donzi.net/ubb/Forum1/HTML/000319.html

I finaly decided the carb and intake were not worth it unless I changed the cam, so I'm in the middle of a cam change right now. Also, I agree with PaulO, you need to install a drive shower.

[AVickers]

They do make a "heavy duty" Alpha.

It's the 1.32:1 unit that came w/ Big Blocks in the late 80s. I don't really know that it's heavier duty, but I've heard that the shafts and gears are supposed to be metallurgically tougher. It might be that with the taller ratio, there's less strain and end pressure on things so they last longer...

The props spin faster on these drives so you may have to change pitch with your setup...

Also, Konrad makes an Alpha replacement called the Omega (get it?). It also has "limitations" and isn't garanteed with engines over 300HP. I don't know anyone who has an Omega and can't find out too much specific on the drives.

[EricG]

I'm realatively new to the world of Outdrives, and I'm a little unclear as the what a drive shower is. I found a couple on the CP performance site, but can they really be that simple?

I've got a stock 88 350 magnum (270hp), and an alpha with about 480 hours on it, would a shower help prolong it's life, or is it not really worth it for the "light" HP load? Thanks.

EG

[rayjay]

If I remember correctly, someone either makes or modifies gears and shafts for Alpha's that are heat treated. I don't remember if it is BAM or one of the other off-shore hi-po parts houses. But if you look in the Marine Links in offshoreonly.com you should be able to find these parts. There are many more upgrades for Bravo's, but there are some for Alpha's.

Speaking of drive mods and up-grades, has any one had experience with the drive extender / sternjack from Land & Sea? See http://www.LAND-AND-SEA.COM/public/marine/stern-jack/sternjack.htm .

I was told that if you see white edged spots on the drive, then a drive shower would help extend the life of the unit. The white edged spots were supposed to be caused by the water vaporizing on the drive from the heat inside. Check HOT BOAT for their drive shower test as they found considerable differences in how well the shower worked because of the shape and style of the water pickup.

Does any one know what is the HP design limit on Alpha's? The SS version? rj

[This message has been edited by rayjay (edited 07-14-2000).]

[Emmo]

A drive shower is actually what it sounds like, it picks up water and sprays it on top of the drive.

http://www.driveshowers.com/images/summit.jpg

There is a good explanation of drive showers at http://www.driveshowers.com/reviews.htm

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Emmo mailto:emmette@emmette.comemmette@emmette.com</A>

[PaulO]

I did some reading and finally settled on this one: http://www.driveshowers.com/faq.htm

[Riley]

Wow! Hey guys, thanks for all of the quality info. I'll be ordering a drive shower on Monday!

Regarding the intake manifold, does anyone have experience putting the Performer RPM in an 18' Classic? I'm especially concerned about any clearance problems you might have encountered. I'm not expecting any miracles by going to the 4bbl, but an additional 1-2 mph would be welcome.

I'm going to be testing 3 different props this weekend, if I find any useful info I'll run another post.

Thanks for your help.

Chris

[PaulO]

Riley,
I have the Performer RPM on my Mercruiser in my '73 18. It's close but, it makes it. By the way, there is some controversy surrounding installation of aluminum manifolds on raw water (especially salt water) cooled motors. I decided that the manifold was cheap enough and I would keep an eye on it. Before installing, I coated the inside water passage with lots of rustoleum paint and installed a pencil zinc into the passage.
PaulO

[Riley]

PaulO,

Thanks for the clearance info. I just hope the hatch on my 1999 has the same clearance as your 73! I'm not too concerned about using the aluminum manifold, I ran an Edelbrock Torker on a 350 Chevy my dad and I installed in a 1956 18' Chris-Craft. Manifold seemed to hold up fine (it's still in the family). I'll tell you, that old Woody would fly with the hot small block! I think it would probably out-run my Donzi with the 305.

Thanks again,

Chris

[Forrest]

If the the Edelbrock Performer RPM intake is a little too high, check out the Weiand Stealth intake. At $99 ( Summit Racing Equipment (http://www.summitracing.com))it's cheap, it's a little lower than the Edelbrock, and it's good - especially with a little more cam and other breathing improvments.

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Forrest

[Riley]

Forrest,

Thanks for the tip on the Weiand Intake. I'm familiar with the Stealth, and it is a quality piece. The problem is, my little 305 is equipped with the Vortec heads. I'm led to believe they are great heads for the small block chevy, but aftermarket intakes are limited. I think Edelbrock is the only company making manifolds for the Vortec heads at this time, so I'm stuck with either the Performer or Performer RPM. The Performer would probably be adequate for what I'm doing right now, but I'd like to upgrade to a 350 this winter, and if possible use as many of the pieces from the 305 as can.

Thanks again for your ideas.

Chris Riley

[Hotboat]

The Edelbrock Performer and the Performer RPM for the Vortech heads are basically the same height (.03 difference). So the height of the either intake should work. However, the height on the Performer RPM for the standard heads is .70 taller than the Performer. 3/4" can be critical in some situations. Especially us guys without the molded in scoop.

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Hotboat

[PaulO]

Riley,
I have a small factory scoop on my decklid but, the flame arrestor does not go up into it. Your dedklid should have the raised center portion and therefore, have more clearance than mine.
PaulO