4.3 performance upgrades

deafwish · **Posted:** Wed Aug 15, 2012 3:19 am

ric wrote:

some do.

On a production marine engine?! Which one?

I'm only aware of an Autronic system where it uses a wideband O2 sensor for real time target AFR open loop tuning.
I'd hazard a guess that Volvo & Mercruiser wouldn't use this technology, but use a marinised, basic automotive ECU.

rpengr · **Posted:** Wed Aug 15, 2012 10:33 am

If 275 HP is realistic, then 365 HP is realistic from my 5.7GS with the same mods?
(Same engine + 2 more cylinders) I'll be watching.

Just for curiosity, what is the easiest (cheapest) way to bump my 5.7 up from stock 250 HP to around 300 HP without sacrificing fuel economy? Currently have 2bbl Holley 600cfm. It is running great on 87octane E10 with timing set advanced.

ric · **Posted:** Wed Aug 15, 2012 10:46 am

rpengr wrote:

If 275 HP is realistic, then 365 HP is realistic from my 5.7GS with the same mods?
(Same engine + 2 more cylinders) I'll be watching.

Just for curiosity, what is the easiest (cheapest) way to bump my 5.7 up from stock 250 HP to around 300 HP without sacrificing fuel economy? Currently have 2bbl Holley 600cfm. It is running great on 87octane E10 with timing set advanced.

GM's Vortec 350 (what you have) is rated for 330hp out of GM's factory doors. VP tuned it down to 250 for sales as a lower hp engine. Going to a good 4bbl intake and carb (holley 600cfm vac sec) will get you started good, but you'll have to swap cams as VP took out the good one and put a crap one in. The GM Performance Ramjet 350/HT383 crate engine's cam is also Mercruiser's hot marine cam for their bigger hp 5.7's (300+hp). You can pick em up for under $200. Easy swap if you ever messed with engines.
http://paceperformance.com/i-6255412-14 ... t-350.html

You won't notice a fuel difference at normal cruise...

mark '87 930 · **Joined:** Wed Sep 05, 2012 7:40 pm **Posts:** 1

Any updates on this? I have a 4.3GL also and am VERY familiar with engines and a 350... this doesnt' seem any different..

ric · **Posted:** Wed Sep 05, 2012 8:01 pm

Im up to 56 mph with the 2bbl and 23p alum and getting redline 5900. My next upgrade is a ballistic 23p.

TX H210SS · **Joined:** Thu May 27, 2010 9:10 am **Posts:** 1488

If you can get that cuddy up to 60 nmph you may get to do the Crash Dummy Tango like in the other post.

ric · **Posted:** Wed Sep 05, 2012 9:35 pm

TX H210SS wrote:

If you can get that cuddy up to 60 nmph you may get to do the Crash Dummy Tango like in the other post.

Feels better at 50 in the stingray then 35 in the h180. Totally different hulls. It doesn't even get stable til around 30 it might be a cuddy on the outside but underneath is their latest design speed hull. Takes corners like on rails as Richard Gere would say. When I can break the 60 mark I'll give it a rest and according to Stingray's performance data it's a prop and a good day away.

TX H210SS · **Joined:** Thu May 27, 2010 9:10 am **Posts:** 1488

That sounds like what the El Capitan racer boat driver of the Formula said, before he road the beast.

Sounds like you are sure winding that 4.3 up a little tight...keep doing that and something is going to sling apart. I have rebuilt a few engines and helped others do same on drag racers....common theory is to build it fast and run it at around 80%...that is theory of those who return to race again and again anyway.

Just throw some go juice bottles on there and you will hit your speed....once anyway.

ric · **Posted:** Wed Sep 05, 2012 10:14 pm

I've considered a 50 shot under the carb kit that could be removed if a warranty claim needed to happen, but rpm wise I'm already hitting the border of iffy so adding that won't help. Need more bite but I'm working with a 1.7 lower. It's going to take a big dia. 23p speed prop to reach my goal.

According to stingray's official radar speed tests they were able to get the fastest speeds.. almost 65mph.. out of a Mercury VenSura Offshore outboard 4 blade prop modified to fit the VP outdrive... but it's rare, discontinued, and expensive. The Ballistic 3 blade is the fastest one that can be purchased and fit out of the box.. around 61mph.

www.iFourWinns.com

4.3 performance upgrades

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