Wideband O2 sensor install

[nola mike]

Been talking about installing an A/F gauge since putting in the Edelbrock 1409. Since the boat is (for now...) running well, I did "fun" stuff a couple of days ago (shift cable repair wasn't fun I guess). Cleaned the boat for the first time since it was dunked more than a year ago. Polished, waxed, cleaned/oiled teak, vacuumed out all the residual sand, etc.

Got A/F gauge/wideband O2 kit and Hardin spacer to fit between elbow and manifold. @Scott06 did this previously and gave me some tips. Figured I'd document the install and tuning. Fairly straight forward with a couple of caveats.

Was able to separate the elbow from the manifold without completely removing it, the shift plate, or hoses. I did remove the canon plug. Gasket was pretty intact and only stuck to the manifold side, so wasn't too bad to scrape off.

Hardin calls for using 2 open gaskets. I have the partial restrictors on there, and decided to keep it that way. Only issue was that the bypass holes didn't line up with the passages on the spacer. I drilled a hole in each gasket to line up with the spacer holes. Don't know how necessary this was or what the purpose of the holes are (just to bleed air I'm guessing). Spacer with holes on top, gaskets with drilled holes (2nd holes from left) beneath:


Second big tip from scott was that the pipe plug on the manifold interferes with the O2 sensor. You wouldn't notice this until you put everything together. I ground the plug down with the elbow out of the way. This would be extremely difficult with it installed.



Other thing is that you need new bolts 1" longer to account for the spacer. 3/8-16 x 6.75". Turns out that these are difficult to find locally. 8" are available, but partially threaded. Cutting them down and you'd lose your threads. Not proud of it, but temporary solution is to use 18(!) washers on each bolt. Trying to find some 7" grade 8 bolts, but the usual online sources have them end up at $30 or so for 4, which hurts. I don't know that I need grade 8 for this application, I did find some 7" grade 5s that I might use.



Lastly, what should have been some straight forward wiring of the gauge into the ridiculous daisy-chained rat's nest of wiring at the helm. I should install a couple of proper busses. But didn't. Can anyone guess the useless gauge that I replaced?

 

[nola mike]

Now on to the tuning! Unfortunately, the gauge is kind of wonky. It will read steady at times, but then just cycle like crazy and peg full lean. Seems like it happens over 3500 rpms mostly. It will occasionally settle down enough for me to get an idea where it's at, but not enough for my liking. So far:

Idle is around 12. I can't lean out the carb enough to change much as far as A/F or idle/vacuum, although it does make it leaner coming off idle (15-16), enough to get it surging at 12-1500 rpm.

Hitting the gas from idle also caused it to run rich, 10-11. Moving the accelerator pump to its lowest setting changed it to around 12. Not sure if this is expected behavior or not. No hesitation on acceleration.

Cruising: 3k-3500 rpm reading 14.5-15.2. Mostly on the lower end of that. Might be slightly lean, but I'm not sure that I'd want to change it?

WOT: Unfortunately, this is where I'd like most to measure it, and that place that the meter flaked the most. A couple of times I thought it wanted to be at 11-12, but I can't be sure.

I'm going to have to get some more reliable numbers out of this thing. Going to double check the connections. Otherwise not sure why it would fluctuate so much. Sensor more likely to fail than the gauge I'd think...

But this is fun.

 

[Scott06]

Mike nice write up interested to see the results.

The 7" bolts are availble from mcmaster carr pk of 5 $16 plus shipping but they need cutting a hair too

The cup holder in my helm worked nicely for a temporary mounting..

 

[nola mike]

Mike nice write up interested to see the results.

The 7" bolts are availble from mcmaster carr pk of 5 $16 plus shipping but they need cutting a hair too

View attachment 384415 The cup holder in my helm worked nicely for a temporary mounting..

Yeah, shipping is $15

 

[Scott06]

Yeah, shipping is $15

that's barely a bar tab in this sport....

You can use grade 5 as thats is what barr supplied me with their manifolds and elbows

if you are fat at idle and mix screws do nothing would suspect your bowl level is too high or one of the floats/needle and seat is getting overcome. I wouldn't expect that to then give a lean wander at 1500-1600 rpm ...

Wouldn't worry about the really rich on acceleration at this time as long as there is no hesitation.

I would think on cruise you want to be a tad richer than where you are. At WOT I think you want to be around 12.5 to 13 I'll have to look it up again... I think Innovate Motorsports had a guide with what AFR to target in marine applications

if it is cutting out wonder if it isn't grounded (sensor) or sensor is bad would run that by tech support

here is a couple

This is the one I was thinking of https://www.innovatemotorsports.com/tuning-a-marine-carb/

Marine AFR

Taking this course will give you a solid understanding of how and where to set the air fuel ratio when tuning any engine.

www.hpacademy.com

 

[nola mike]

I'm wondering if this thing is real sensitive to power fluctuations. I tried direct wiring the positive and negative (individually, cause I'm lazy) with no change. Pt it back, and it works occasionally. Found that the ratio is 14.2-14.9 mid range, and then fattens it over 3500 rpm. Gets into the 13's over that, and then into the 11's at wot. So now the fun! What to change? All my rods jets and springs got dunked. Managed to clean up most, but can't find any secondary jets. I have a vacuum gauge on there but didn't compare it to the af readings. I'm guessing that over 3500 I'm getting into the fat part of the rods. Less than that I'm ideal. I think my options are to decrease my primary jets and use softer springs, or just stiffen the springs so I don't get into them until real late. Really having 2 stage rods in a boat never made much sense to me. Obviously secondary jets need to be smaller. I wonder if I'm leaving meaningful hp on the table running that rich at wot?

 

[Scott06]

I'm wondering if this thing is real sensitive to power fluctuations. I tried direct wiring the positive and negative (individually, cause I'm lazy) with no change. Pt it back, and it works occasionally. Found that the ratio is 14.2-14.9 mid range, and then fattens it over 3500 rpm. Gets into the 13's over that, and then into the 11's at wot. So now the fun! What to change? All my rods jets and springs got dunked. Managed to clean up most, but can't find any secondary jets. I have a vacuum gauge on there but didn't compare it to the af readings. I'm guessing that over 3500 I'm getting into the fat part of the rods. Less than that I'm ideal. I think my options are to decrease my primary jets and use softer springs, or just stiffen the springs so I don't get into them until real late. Really having 2 stage rods in a boat never made much sense to me. Obviously secondary jets need to be smaller. I wonder if I'm leaving meaningful hp on the table running that rich at wot?

Do you have this edelbrock tuning manual ? https://www.edelbrock.com/media/wysiwyg/documents/carb-owners-manual.pdf

the secondary uses the same jets as primary, just different orrafice size.
the reason you have two step rod in any application is so you can have a different fuel mixture at part throttle and wide open throttle. The spring used is the point at which the spring over comes the vacuum ( decreasing as throttle opens) holding the step up rod down in lean mode. When it pops up at lower vacuum setting it goes to rich or power mode.

a stronger spring will make it go rich sooner or at a lower throttle opening/ higher vaccum setpoint.
not sure what is in your carb now but since your part throttle is near ok would try a step up rod with a bigger diameter in the rich (up) position. if you have the stock rod (.068 x .047) ,

try position 22 on the eddlebrock chart page 14 in the manual which is an .065 x .052 step up rod. This would richen your cruise a hair and lean the wot . see what afr this gives u. You may also have to lean out the secondaries, but now sure how much the secondary air valve opens on a 4.3 as it doesnt need too many cfm. Maybe try an .095 jets as they are two steps lean.

the chart helps a bunch as you need to walk in both cruise and wot.
this thread is rick stephens 4.3 1409 tuning https://forums.iboats.com/threads/stumbling-edelbrock-1409-4-3l-v6.670697/

 

[nola mike]

Yeah I have the manual. I don't remember what I ended up with as far as combo. The secondaries do open, and then I see it really richen up. I know that my secondary jets are richer than stock, so need to go back down. The problem with a marine application vs auto is that there really isn't a part throttle condition. In a car, you lift off the throttle and have a high vacuum condition, and at that point you want to lean out your mix. There isn't really an analogous situation in a boat. When I put the carb in I had a vacuum gauge attached. The vacuum decreases pretty linearly until you're near 0 at wot. I'm going to test again, but I pretty much guarantee that I'm running 14.5 until I reach whatever vacuum my springs are, at which point I richen up. Really I want it to be linear I think throughout, so either riding the skinny or fat end of the rod throughout the rpm range. I'll confirm this next time out, and see what I have on there now vs what parts I have on hand.

 

[Scott06]

Yeah I have the manual. I don't remember what I ended up with as far as combo. The secondaries do open, and then I see it really richen up. I know that my secondary jets are richer than stock, so need to go back down. The problem with a marine application vs auto is that there really isn't a part throttle condition. In a car, you lift off the throttle and have a high vacuum condition, and at that point you want to lean out your mix. There isn't really an analogous situation in a boat. When I put the carb in I had a vacuum gauge attached. The vacuum decreases pretty linearly until you're near 0 at wot. I'm going to test again, but I pretty much guarantee that I'm running 14.5 until I reach whatever vacuum my springs are, at which point I richen up. Really I want it to be linear I think throughout, so either riding the skinny or fat end of the rod throughout the rpm range. I'll confirm this next time out, and see what I have on there now vs what parts I have on hand.

When you are cruising along 3200-4000 rpm that is part throttle, not highway cruise which can go leaner than 14.7, but it it not WOT acceleration.
if your cruise is basically ok you just need a leaner rod on the rich/ power end and leaner secondary jets. probably want to get the afr tweaked in then play with the springs to work on how much throttle it takes to go rich.

be interesting to see if you can see how much the secondary air valve opens as not sure how much influence over wot mixture is the primary rod and jet and how much is secondary jets

 

[nola mike]

Took it out today and had my first mate check vacuum readings at different rpms. Af gauge working fairly consistently now except for occasional hiccups. As stated, I think it's sensitive to the 1v or so voltage fluctuations that I sometimes get at the helm.
So most vacuum is 20 at idle. It never gets lower than that. From there it increases fairly linearly until wot. Here's what I get, more or less:

Rpm. Vacuum. A/F
1k-2500. 18-12. 13-14
25-3300. 12-10. 14.2
33-3600. 10-8. 14.5-15.0
36-4100. 8-6. 12's
4100+/wot 5-2. Low 11s

So my cruise mix is good until about 3300, then leans a bit before getting too rich. It gets rich right at around 8 in, which is cool. I assume that it's getting into the fat part of the rod and I have 8" springs in there. Another dramatic drop when secondaries open.

I need to lean out the power mode, and would like to have it come on a bit earlier (10"), but it looks like the softest spring is 8". I was hoping to have everything available before breaking into the carb, but since I don't remember what's in there now I guess I need to find out and go from there. This is as much fun as I hoped btw.