On May 22, 8:55 pm, "jamesgangnc" wrote:
Your carbs will probably be fine. Your mods will increase the overall flow
at higher rpms but that will probably not require a jet change.

I hate to burst your bubble but there really is very few tuned marine
manifolds. To really tune an exhaust you need the individual pipes to be
longer than is practical in a water cooled marine manifold. That's why
automotive headers look like they do. Tuned headers also have the
individual lengths adjusted so that the exhaust charges line up in
succession as they are combined at the collector. That enhances the
scavenging effect of the exhaust. Which is also compromised in near-stock
marine engines because of the reduced cam overlap to prevent water ingestion
at idle in a wet exhaust. It's tough in the marine world :-) One thing
aftermarket manifolds do well though is get rid of 80lbs or so of cast iron
at the back of the boat.

"Rainmann" wrote in message

ups.com...

Greetings,

I am in the process of rebuilding both of the Merc 350's in my boat.
I have added some performance mods, so I know I will most likely need
to re-jet my Qjet carbs. I am seeking some advice for a good starting
point on the jets. Below is a list of the high performance add-ons.
Thanks!

Qjet 17059280
Edelbrock performer intakes
MSD everything
Comp roller rockers (1.52)
Comp Extreme Marine cam 262/268, .462/.477
Tuned GLM manifolds, open exhaust
K&N flame arrestors

Not real screamers, but should have significantly more performance
over stock. Any advice will be greatly appreciated! thanks

--Ray



Thanks everyone for the information. Your input is appreciated.

As far as the noise goes, yes the sound of twin small blocks is
awesome, albeit extremely loud. But, I have Captain's Call exhaust so
it can be turned off with the flip of a switch.

The exhaust manifolds have short runners cast into them. Not quite
shorty headers, but light years better than stock. Not to mention
jacketed headers start off around $2500 per set. The problem with a
twin engine boat is, you have to buy two of everything. Gets
expensive fast!

I also forgot to mention that I have purchased Vortec heads with some
mild port work. The combination of all this should produce
significant more HP and torque over stock.

--Ray