Carb jetting ??
 

Got a new to me 572 cid all aluminum,nat asp. with cmi big tubes.Guy I bought it from claims 800 hp. but I'm not sure without a blower on top.The boat is a 22 Talon i/o with a 1.36 modded bravo swinging a 28 hydromotive apx 5800 easy.I sent the carb off to be cleaned and gone thru ,"Williams Carbs in miss " they are the ones who had set it up originaly and the boat had been sitting a while prior to me buying it. It has 92 jets all the way around and is real rich,darkened the plugs in about 5 trips to the lake.It is a 1150 dominator I just went down to 90's all the way around and about to put in a fresh set of plugs.Do most of you just read the plugs or watch the speedo and tach for correct jetting ? Is there a better way to select the correct jets ? What spark plugs are you running in a simular setup ? thanks ,I got lots to learn I been an outboard guy for long time and this is my first big block. hf...

O2 bungs and AFR's. The most accurate way to jet.
Innovate LM-1 or LM-2

There are several good articles on the internet on reading plugs. To put O2's in my headers would ruin them so I read plugs and change jets 2 sizes at a time until I'm close. When I make a jetting change, I let it warm up and make a couple of good hard passes and pull a couple plugs. I check it right after I make changes to make sure I'm not hurting anything.

the o2 bungs go in the tailpipes

fixx
 

i have another way of doing it with out welding bungs into the header and if your good you can do eacy cylinder:thankyouthankyou:

Yep. Also, FAST EFI makes a nice one. Mike Tkach and I have one. Dual channel.

As for the bungs, like Mike Said, install in the tailpipe, after the collector. It reads a average of all 4 cylinders on that bank. I prefer to read both banks, because sometimes the AFR can differ a bunch between banks. Although on mine, they were within .1-.2 of each other.

If you try to tune it like a race car, you just may end up with some pistons for paperweights. With todays fuels, I just dont trust plug readings for what we are doing. I'd rather take advantage of modern technology and put the meter on it, it wont lie. And if your fat in the midrange, or wot, or lean, etc, you can really dial it in. What you'll save in wasted fuel will pay for the meter in one season, and your engine will live a happier life.

Is the 1150 Dom a 2 or 3 circuit carb ?( how many air bleeds per barrel?) if it is a 3 circuit carb they have a problem with running extremely rich in cruise , people think they need to lower the jets but that only leans out the VERY top of Wide open throttle!!!!!

If it is a 3 circuit carb the intermediate calibration is way to rich for a marine engine ( fact not my opinion). Send carb to a shop what is capable of re calibrating the intermediate for marine cruise use.

A wide band 02 or a gas analyzer are the only ways to tune a carb these days. The oxygenated fuels don't read very quickly or accuritely

But if the carb is a 2 circuit you can lower main jets but as I said be careful reading plugs its old school very difficult to read today's fuel

OK, how do you do each cylinder?

O2 sensors don't work wet, I think most of us have wet exhaust so tailpipes are out. I talked to Lightning and they won't add O2 bungs to headers once they're built.

Here are 2 easy ways to install 02 bungs

If you have tail pipes install the bung close to the header flange (2"-3" back) use a 1" hole saw and drill through both outer and inner pipe. Weld bung on outside of pipe and then on inside of pipe.

If you cannot install the bung close enough to the flange so you cannot reach inside the pipe to weld here is another method ;
Get a 1" stainless steel fender washer measure to outside dia of the washer ( approx 2 1/4"). Drill outer pipe 1/16" smaller than fender washer. Drill inner pipe 1" dia( size of bung). Weld inner pipe through the space in the large outside hole, then place fender washer over outside of bung to cover big hole . Weld washer to bung and weld washer to pipe.