I feel your best fuel economy would be achieved by using a Quadrajet and keeping out of the secondaries over the 2bbl.

Good thinking...but in real life this doesn't work. The boat won't have enough power to plane with using just the primaries.

I know this, because of I have done this live more than a dozen times. IE: People that tell me secondaries don't open until a higher rpm. I disconnect the secondaries and the boat won't plane. Yup, even 20ft and under boats with very little weight.

The primaries are just to small.

Also, as i referred to...the secondaries do open at planing rpm. Again, if they don't, the boat will not plane.

The load - boat/gear/fuel/etc,etc - is responsible for how much hp you need for X mph. HP used determines how much fuel you use.

For what it's worth, Volvo sells a 5.7 rated at 250HP. It has a 4bbl intake with an adapter and 2bbl holley carb. That same engine with TBI on the same intake is rated at 320 HP. I have converted several from the 2bbl carb to a 4bbl carb. They all picked up a noticeable amount of performance and every owner said the economy improved.

The reason Volvo and Merc offer these packages is strictly price point, not performance or economy. Basically they are detuning the 350 Mag, because the engines are identical other than the fuel system.

Heh Bob, it's CFM.

The Volvo package was good...to up the HP over the Merc set-up.

It used a bigger 2bbl than merc does, but more importantly, as you said, it used an adapter on a 4bbl intake. The adapter and intake both increase airflow a good amt.

I've done a bunch of 2bbl to 4bbl too.........and it's a crazy good upgrade.

The 2bbl stuff, just like when Chevy and other companies did it on V8's, is exactly what you said ....was strictly price point.

Want more power ? Give us extra money.

So SB what do you think about that motor?? The 383 in the link.

Chris

The flat tappet setup, hypeuretic pistons, stamped rockers, and valve springs good for .530 lift, with .462 lift cam, aren't my idea of a great setup, but not surprised with the price of it. 420HP they say, I'd tell them let me bring it to MY dyno, and see if it makes 420HP and 430ft lbs.

Stay the phuck away from that company!!!!!! THey have a LONG history of changing names and royally screwing anyone that does buisness with them, Your better off taking the briggs and straton off the lawnmower and running that in your boat than one of theirs. dead giveaway to the company is the tacoma and or kent address and 7 year warrenty.

Phragle, lay it out brother, tell us how you really feel. LOL.

Sounds like a pass to this company, Time to find another.

Well I could have cheered him on and waited for the inevitable 320 page "I got phucked in the azz by an engine builder without so much as a reach around" thread..... But despite what my Ex says, Im really not a sadistic azzhole... (I just play one on tv)

Don't let us stop you.

I'm going with my Phragle feeling - lol - and say it's a hunk of schit.

For your needs, why not go with a brand new GM marine vortec 350 longblock, around 2700 bucks I think.

This seems an appropriate place to share my latest experience with one of these rebuilders(not the one mentioned). Had a customer buy 2 of the 400 HP 383's to replace his tired 6.2s. They came with a 7 year warranty. He brought them to me to dyno and tune. On the dyno they smoked and only made 350 HP. He put them in the boat and ran it for a couple of hours. He called me back and said they were using oil like crazy and brought them in for me to fix. Here's what I found when I pulled them apart. Scat 3.75 cast crank, KB Hyper pistons. Those are the only parts that were as represented. The rods were the old style 350 with stock bolts. The cams were hydraulic rollers that were reground stock cams with .530 lift. The heads were stock vortec, so the retainers smashed the valve seals. Additionally they replaced the valves with the older style that have 2 grooves, one for the keeper and one for an O ring. The second groove would drop into the valve seal, further breaking it. There was tons of debris in the engines, pistons and bearings seriously scored.

I built him new engines and all is well, but he lost a ton of money. He asks me on our test run what kind of warranty they had. My reply was, "well you know what good a 7 year warranty did you, if these screw up
we'll fix em" That's our reputation on the line and custom builders don't stay in business screwing people.

Bob Lloyd
Full Throttle Marine

7 year warranty, probably same guy different name....

Not surprised whatsoever Bob!

Wow guys.. Thanks for the info.. Including you SB.. I sort of figured the deal was too good.. So now I will prob look at a mercruiser 350 mag reman or something else.. Great to have sharing of info like this.

Chris

some people just dont get it,YOU GET WHAT YOU PAY FOR,and sometimes you get less.the 7 year warranty should have been the tip off,no body gives a 7 year warranty on an engine!