When using those Cast Iron Bowtie Intakes (awesome btw - as good as Eddy Performer RPM intakes) on stock Merc 350 Mag engines I used DA secondary rods. Cheap, and good tune. Nothing different on primaries.

SB, wish I could remember the exact metering rods... seemed to me there was a "C" somewhere in the sizing. It was the same secondary metering rods from the 350 Magnum which was rated at 270 h.p.
If I remember correctly the Magnum came with the high rise intake, taller flame arrestor and 4" risers instead of the 3" risers from the Merc 260. Those were 10 of the STRONGEST horsepower in
upgrade history! I'm guessing it was at least 30 h.p. stronger. Either the 270 was underrated or the 260 was overrated. Another inexpensive upgrade (if the engine is out) was adding a windage tray in the
oil pan. I don't remember the exact price but I think it was under $50 including the new maincap bolts (4) and the tray fasteners.

if you were to go to performer RPM air gaps, you might see 2 mph increase...hope that answers your question

Wes, maybe CY rods ? In the following chart they look identical to DA's ?
http://www.thirdgen.org/rods

I installed many of these intakes to small lightweight single outdrive Alpha outdrive'd boats.
I would also use Felpro #1204 intake gaskets that blocked off the heat riser / exhaust crossover passages. If carb had typical choke (ie:not electric) I would remove choke plate from carb. If person just had to have choke, I'd drill 1/2" hole in block off plate on the side of the heated choke mechanism. Around here in the summer, you do not need a choke. Merc no longer sells the required longer choke rod for use of these intakes. GM no longer sells these intakes anyway. Bummer ! Probably sold 50+ of them.

Anyway, performance from these small boats would indicate near 15hp and with Felpro#1204 gasket around 18-20hp.

Great mod for small lighterweight boats that respond to most everything.

And the nicest thing about changing secondary jetting in Q-jets is it is literally a 5 minute operation, if that. Single screw to undo the metering rod hanger, pull them out, and change them. Done. You can literally do while the engine is running.

SB, I am remembering using "CP" metering rods in the secondaries when I switched to the Hi rise iron intake manifolds on my CC Stinger. Once I got the taller flame arrestors and the jetting correct I felt it was the best bang for the buck I did on that boat. I went on to try different heads, cams, and roller rockers.
Bottom line for my Stinger was stock it would turn (1:50 Alpha drives) 21" 3 blade clevers to 4200 r.p.m.s. I could then trim it out to reach 4600 r.p.m.s. With the hi rise setup it would hit 4600 r.p.m.s with the drives tucked all the way in. It would trim out to 5,000.

I didn't block the heat risers as I boated year-around in the Pacific Northwest. I had a full top and a Red Dot heater (after I went to fresh water cooling). We even took the Stinger out when it was snowing!

Wish it was as easy to make "mini mods" on the 6.2 MPI s! I'll probably just settle for blueprinting the props! BTW I enjoy your posts.

I would go along with this and add a set of holleys or Barry grants on top. Yrs ago I read an article where they took a stock motor and swapped the intake and carb and gained 22 hp. But I don't know if it would gain u much in speed. I had a 88 260 that I swapped out the junk iron intake and q-jet for a air gap and holley and gained 5 mph on the junk stock speedo!!

Might be, however leaner than what I ended up with. Again, many of the high rise cast iron bowtie intakes I used on stock 260hp motors - and modded of course - had Felpro 1204 intake gaskets, closing off exhaust passage that heated the intakes, choke removed, and many also got a lifter valley tray that kept the hot oil off the intake. So...can't answer for your deal...just mine.

Here's a Merc tidbit i found:

http://www.boatfix.com/merc/bullet/93/93_15.pdf