First Run of the season

[CnV & Family]

Yes... The Donzi is back in action!

We got our first run in this past weekend. Man was I glad to get it fired up again. I've new info and a few more questions!

We got a 126 x 26 prop on her... I found the stamp. It was smaller than I expected. All the family was in and with 3/4 tank we hit 55 MPH solid. 52 before trim adjustments. Guage stops at 55... :) The bad news is the tach is bouncing between 20-30 like it has a bad connection somewhere. So I have no idea where I stood in regards to RPMs. I traced the wires as best I could and found nothing loose or disconnected. Time for a new tach and speedo? I'd like to keep original so maybe I'll just look at replacing tach and use a GPS...

Here's my wish list so far...
GPS
Upgrade to 4bbl carb
Add K&N Filtration / Arrestor System

In theory, what kind of speed increase should a carb and air intake make?

-C

[CnV & Family]

I see that CFM = ci * MaxRPM / 3456

According to Mercruiser's specs I don't see the 4.3LX, so I'll go with 190HP 4.3L rather than the 205HP 4.3LH.

It seems to be a given that nothing should exceed 4900 RPM unless you really know what you are doing.

So that's approx 270 CFM. Looks like a 4bbl would be way overkill at 600CFM.

Given this, what is it that requires the CFM to increase? Is it ci only? Would I just be throwing money at nothing if I were to look into a carb and filter? Seems like the math says I would be...

Would anyone want to take a shot at telling me a general rule of thumb on how to spec everything together in general? I'm nowhere near adept in mechanical or engines... Given that my setup is basic and very common, I don't want to be told the best setup. I want to learn all about how this stuff goes together. I'll gladly do the research if someone could point me in the right direction!

[RPD]

if you put on bigger carb, higher FLOW rate, the air/fuel VELOCITY goes down... if you go too big the velocity will drop too low and you might not like the way it performs.... open the throttle too quickly from idle and it will just bog, or even stall....600 cpm is probably way too big for the 4.3L