Ok, 496 Merc Mechanics : Fuel pressure?

[Beer-30]

I just put a gauge on my HO, fired it up. It won't really idle anymore with the stick all the way back. I have to push to stick about 3/4" forward to maintain 700-800 idle. Smells real rich, and I have been having a nasty soot problem.
So, I fired it up and the gauge reads 36psi at idle. Romp on it, and it goes up a few pounds, so it looks like the regulator is adjusting somewhat.
The question is, what should the idle FP be? The book says 6psi running?

[Dave_N]

Book says 43PSI, key on, engine off, pump running. 36 is low, but that should not cause a rich condition, unless it was due to a leaking injector. Rich condition could also be due to a bad sensor.
Since you did not mention it, I guess you are not getting any engine alarms? Do you have a smartcraft display or scan tool?
Dave

[Beer-30]

I don't have the SmartCraft display.
I have scanned it twice, when I took it to the mechanic. 1st time I had an unplugged exh sensor that was giving the beeps. No codes or beeps as of right now.
Fire it off and it just starts surging. FP is stable at 36. Constant surge. No beeps. Push the stick forward about 3/4" off of the idle stop and it smooths out to 7-800.
So, we ask what is the engine wanting? Giving it some throttle blade opening, I am thinking it is wanting more air. My next idea is finding out what the Idle Air Control readings are / are supposed to be.
For surging, the Mercruiser ECM book (#50, I think) says to change spark plugs. I have never had plugs cause surging, but hey....it's worth a shot.
Engine runs great at cruise as well as WOT.
Back on the trailer after a day at the lake, the transom is covered in soot.
Those are my symptoms.

[Beer-30]

Anyone else? Opinions? Ideas?

[steelcomp]

Where did you tap in for the new guage? Was it in the main fuel line, anywhere after the filter, but before the fuel rails? Is there a possibility that you got some teflon tape, or some other kind of debris in the fuel line causing stuck injector(s)??? Just a thought...it wouldn't take much.

[Beer-30]

Where did you tap in for the new guage? Was it in the main fuel line, anywhere after the filter, but before the fuel rails? Is there a possibility that you got some teflon tape, or some other kind of debris in the fuel line causing stuck injector(s)??? Just a thought...it wouldn't take much.
I am beginning to think that.
I put the gauge on the schrader on the fuel rail for the injectors.
A leaking / stuck injector or two would cause rich condition. It is, however, holding fuel pressure. Shut it off, and it stays at last setting. The gauge does not have a check valve, so it is reading real-time residual pressure.
I suppose pulling the plugs would tell alot. Are some dirtier than others type of thing.

[paradigm shift]

I do know that on the 502 EFI if the idle air motor setting or counts are off it will cause this. I am not up to speed on the 496 and how to set though sorry. Check out the link it has more info. Problems are with a procharged 500 EFI but you could pick up something.
http://www.offshoreonly.com/forums/showthread.php?t=52601&highlight=setting+IAC

[shadow]

Anyone else? Opinions? Ideas?
Beer-30,Did you disconnect the vaccum line to the fuel pressure regulator while checking the fuel pressure?Make sure you disconnect the vaccum line to the fuel pressure regulator,this is a must to get proper fuel pressure reading.

[Dave_N]

It does not sound like an IAC issue. A bad IAC valve will usually cause an alarm. Sounds more like a sensor or leaking injector. But your probably going to need a scan tool to figure it out.
In any event, from what I have seen, the following graph is typical of how an IAC (on a 496HO) will function at startup (note that engine RPM is divided by 10). It will go to 99.98% right away and then drop after a couple of minutes of running and become very active around 20% to 30%. Keep in mind that other problems will affect how the IAC operates.
Dave
http://www.hometown.aol.com/newprtdave/496iac

[Beer-30]

Beer-30,Did you disconnect the vaccum line to the fuel pressure regulator while checking the fuel pressure?Make sure you disconnect the vaccum line to the fuel pressure regulator,this is a must to get proper fuel pressure reading.
No, I didn't. I mainly wanted to see if it was fluctuating or not. I have heard of plugged fuel systems causing the FP to "search" and have erratic readings all over the scale. It was rock steady. It jumped up each time I romped on it, showing the regulator was responding to vacuum readings.
I will try that next. I disconnected the fuel gauge, as I was going to take it to the lake tomorrow. Looks like my plans may change, due to some illnesses in the family members that were supposed to go. Anyway, next plan is to change plugs, read the old ones, and put the FP gauge on again. After all that, I will disconnect the vac line and go from there.

[bigkatboat]

The ECM puts out the information, and this is what the DDT sees. The ECM may be putting out the correct signal but if the IAC motor is not operational, the motor won't idle. Put the DDT back on the motor in a static test mode. Run the IAC jog test and put your hand on it while doing so. You will 'feel' it moving (or not), and this will lead you to replace the IAC motor. The "new style" (remote) IAC motors don't have great track record. When the ECM puts out the correct signal, but the IAC motor does not respond, you will NOT get a failure code. The DDT sees the signal, not the actual actions or results. Good luck, and let us know what happens.

[shadow]

No, I didn't. I mainly wanted to see if it was fluctuating or not. I have heard of plugged fuel systems causing the FP to "search" and have erratic readings all over the scale. It was rock steady. It jumped up each time I romped on it, showing the regulator was responding to vacuum readings.
I will try that next. I disconnected the fuel gauge, as I was going to take it to the lake tomorrow. Looks like my plans may change, due to some illnesses in the family members that were supposed to go. Anyway, next plan is to change plugs, read the old ones, and put the FP gauge on again. After all that, I will disconnect the vac line and go from there. I would
hook up a gauge,disconnect the vaccum line and get a good reading before chasing or guessing.May be a simple fact of the pressure is too high.It happened on mine.only mine would load up after long idle,but did get the soot,Turned the pressure down and problem was gone.good luck.

[Beer-30]

I do know that on the 502 EFI if the idle air motor setting or counts are off it will cause this. I am not up to speed on the 496 and how to set though sorry. Check out the link it has more info. Problems are with a procharged 500 EFI but you could pick up something.
http://www.offshoreonly.com/forums/showthread.php?t=52601&highlight=setting+IAC
Thanks Paradigm. All the readings will probably be similar, but the IAC motor is on the back of the intake on 496s. It only has a clean air tube (hose) running from the TB back to the motor itself.
I should, however, probably look at the TB blade set screws. If it or them has or have come loose, this would cause similar situation. Just one more thing to check. I really like trying to trouble shoot these things myself as it get one in depth with their motor.
TPS volts were .53 at idle when I scanned it last.

[Beer-30]

I would
hook up a gauge,disconnect the vaccum line and get a good reading before chasing or guessing.May be a simple fact of the pressure is too high.It happened on mine.only mine would load up after long idle,but did get the soot,Turned the pressure down and problem was gone.good luck.
Will do. I saw the adj screw we were talking about at the river. It actually looks like it has been tampered with, as the paint is boogared already.
I assume one would disconnect BOTH vac lines? the one on the upper (factory) reg and also the Merc one down below?

[Beer-30]

The ECM puts out the information, and this is what the DDT sees. The ECM may be putting out the correct signal but if the IAC motor is not operational, the motor won't idle. Put the DDT back on the motor in a static test mode. Run the IAC jog test and put your hand on it while doing so. You will 'feel' it moving (or not), and this will lead you to replace the IAC motor. The "new style" (remote) IAC motors don't have great track record. When the ECM puts out the correct signal, but the IAC motor does not respond, you will NOT get a failure code. The DDT sees the signal, not the actual actions or results. Good luck, and let us know what happens.
Cool, thanks. That sounds real promising. This surging has come on slowly and is pretty constant now. I was waiting for whatever was causing it to fail, so it would set a code. So far, it has not done that. It has gone from doing it every now and then, usually after running at cruise - coming down to idle. To pretty much every time out of cruise, but would stabilize at idle. To now, not stabilizing at idle at all. That led me to believe that some moving part was not moving anymore - like the IAC motor - since it is idle specific.

[shadow]

Will do. I saw the adj screw we were talking about at the river. It actually looks like it has been tampered with, as the paint is boogared already.
I assume one would disconnect BOTH vac lines? the one on the upper (factory) reg and also the Merc one down below?
you just need to disconnect the one at the upper regulator.to adjust it it is a small tamper proof torx bit.I think it's a t15.I've got the bit at work i'll look at it tomorrow to be sure.sonds like maybe when you had it in the shop before maybe someone has been in there messing with it.if they made an adjustment with the vaccum line connected,the setting will be wrong.Hopefully it's that simple,very well could be!with the line connected it can make as much as a 10lb difference which would load up yor plugs and cause runability concerns.You might want to pull one plug and see if it looks fuel fouled.

[Beer-30]

you just need to disconnect the one at the upper regulator.to adjust it it is a small tamper proof torx bit.I think it's a t15.I've got the bit at work i'll look at it tomorrow to be sure.sonds like maybe when you had it in the shop before maybe someone has been in there messing with it.if they made an adjustment with the vaccum line connected,the setting will be wrong.Hopefully it's that simple,very well could be!with the line connected it can make as much as a 10lb difference which would load up yor plugs and cause runability concerns.You might want to pull one plug and see if it looks fuel fouled.
If it was tampered with, it was before I owned it. But that has only been since Jan / this year. And I am with ya on the adj. Every time an adjustment is made, it has to be done w/o vacuum signal. I left the cover off, so it is easy to continue my shooting. If we don't end up at the lake tomorrow, I will slap the gauge back on it and put the water to it. I'll let ya know.
I checked one plug shortly after I got it, when I started looking at the soot issue. It was black around the outer thread area and on the ground "hook". The electrode itself was clean and white - as was the initial area of the porcelein around it. The rest of the porc toward the "inside" of the plug was black. I'll pullem all and look, keeping them in order incase one or two look worse than others.
If it was a Ford, you would probably have more options for me, eh? :D

[Beer-30]

Ok, changed all plugs to Denso Irridium. All looked pretty good. Still white on the porcelain, dk brown or black on rest of areas. All were firing. None were wet. Doesn't appear any injectors are stuck open.
Taking the vacuum line off of the top reg while running put FP from 36 to 40. Finger over the unplugged line puts it back to 36 - obviously the lower reg is working also.
Going to change fuel filter and check screen at inlet of boost pump next. After that, if still not right, it goes to dealer. :)

[shadow]

Won't help with your soot problem but you might want to check this for your throttle position concern/idle.Take off your air filter,look in the throttle body and check to make sure it is just not a matter of adjustment of the cable.Check both ends of the cable all the way open and closed.

[Beer-30]

Ok. Fuel pressure good.
Cable, throttle assembly good. Full open, full closed.
Changed fuel filter.
Cleaned inlet screen at inlet to boost pump. Some small metal shavings from the tanks, but nowhere near blocked. No other contaminants found.
Irridium plugs smoothed things out a little bit. During the surge at idle, it doesn't die anymore. It used to die on the down side after a few up/down cycles. Now, it just keeps cycling a little smoother. 4-500 RPM instead of 7-800. Still, crack the throttle forward about 3/4 and it smoothes out to steady 800 or so. Just weird. I still suspect IAC. I am at the limits of home tinkering - off to Merc dealer.
Will keep updating.

[James'SS-24]

Check your tps sensor. Both the pulse counts and the output voltage. Mine has done that almost exact thing and that is all it turned out to be. You have to have a scan tool to do the counts but you can do the output voltage with a voltmeter. Should be between .65 and .70 volts @ idle. Mine was also starting really hard and when it did start it was flooded. But any where off of idle it ran fine! Also if this sensor is out of adjustment it won't register a code. :boxed:

[Beer-30]

Check your tps sensor. Both the pulse counts and the output voltage. Mine has done that almost exact thing and that is all it turned out to be. You have to have a scan tool to do the counts but you can do the output voltage with a voltmeter. Should be between .65 and .70 volts @ idle. Mine was also starting really hard and when it did start it was flooded. But any where off of idle it ran fine! Also if this sensor is out of adjustment it won't register a code. :boxed:
The last time I scanned it, it was .57V, which looked normal. Not sure exactly what the range is for idle.

[James'SS-24]

Hey Beer 30! So what was the problem? Always curious about this kind of stuff in case it happens to me! :rollside:

[bigkatboat]

Did you replace the IAC motor yet? Don't forget to use a new base gasket!

[Beer-30]

Did you replace the IAC motor yet? Don't forget to use a new base gasket!
Nope, haven't touched it yet. The plugs smoothed things out a little, but didn't cure it. I figure I will take it in after the first of the year and let them know what I had done so far and that I suspect the IAC. I figure that will be better than just starting to blindly replace parts. I'll keep all posted.

[Beer-30]

Ok, ordered a new IAC motor, since I found the same part number at Marine Power for $62 instead of $90 from Mercruiser. And, yes, I ordered a gasket too. Should be here Thursday. I figure a $62 dollar shot is cheap enough to gamble on saving $2-300 for dealer troubleshooting. Once I get it, I will update.

[purrfecttremor]

This is very interesting but I gotta ask whats a IAC motor? Sounds like one of thoes shity problems that only happen to Me.
Good luck Beer 30.

[Beer-30]

Idle Air Control motor. The computer tells it how much air to let in for proper idle speed.

[Beer-30]

That was it!
I just came in from changing out the IAC motor. Fired it up with the stick all the way back and it just started idling like it was supposed to. It had been consistantly doing the surging thing right off the bat - every start.
I had always tried letting it warm up and trying it again, still surged.
I let it come to full temp and then dropped the stick back to the stop. Nice idle. No surge.
$62 for the IAC motor.
$.79 for the gasket.
I had been waiting for a day when I knew I would have plenty of time to complete it. I had a free evening tonight, so I decided to try it - even if it turned out to be a lengthy process. Two TORX screws, and it came right off. Gasket came off clean. Popped the new one on and cinched it down evenly. Noticed that the clean air feed tube had come off of the IAC base again (it had still surged with or without it - so that wasn't it), so I cinched it to the base with a pair of zip ties.
On a scale of required Coors Lights; one being the easiest - ten being the hardest::
It only took 2.
:D

[purrfecttremor]

Good info for all to remember.Cogratulations now if it was only summer!

[kevnmcd]

Glad to hear it. Wish my fix would have been that easy! :)

[Beer-30]

Glad to hear it. Wish my fix would have been that easy! :)
Hey, ya never know. I may find a loose nut flying around in my motor later on. I've heard this has happend before :)

[kevnmcd]

Hey, ya never know. I may find a loose nut flying around in my motor later on. I've heard this has happend before :)
I have one of those nuts....want to borrow it? :D

[Beer-30]

:crossx:

[kevnmcd]

Beer-30 - Where did you get your fuel pressure guage that attached to the schrader valve? I need to get one....or borrow yours! :idea:

[Beer-30]

Well, you're welcome to borrow mine, but you would have to make a trip here. Or, wait 'till Memorial Day weekend at Havasu. I could bring it then :D
I got this kit, as I have needed a gauge for other cars and am adding more injected vehicles to my collection all the time.
http://www.toolking.com/productinfo.aspx?cid=728&productid=8506
It has an extension hose that would get it down to the back seat or so. If I get into heavy duty WFO testing, I would have my local Aeroquip vendor make me a nice long extension hose to make it reach the helm.

[kevnmcd]

That is a little pricey for what I need. I think I will just buy another small gauge and some fittings. :rollside: Thanks for the link though.
P.S. What rpm does your motor idle at?

[Marty Gras]

Mr Beer 30, you are welcome. This is my "new name", but I will still try to help anyone with 'factory' or 'aftermarket' EFI systems. Just ask. Boats that run that "remote style" IAC will be having the same problem. (sooner or later) They have been known to stick or just go dead. Please post the part numbers and where you purchased the parts, for those who will need them.

[Beer-30]

Mr Beer 30, you are welcome. This is my "new name", but I will still try to help anyone with 'factory' or 'aftermarket' EFI systems. Just ask. Boats that run that "remote style" IAC will be having the same problem. (sooner or later) They have been known to stick or just go dead. Please post the part numbers and where you purchased the parts, for those who will need them.
Um. Ok. Thanks. Will post part numbers in a bit.
First of all, what was your old name.

[Beer-30]

That is a little pricey for what I need. I think I will just buy another small gauge and some fittings. :rollside: Thanks for the link though.
P.S. What rpm does your motor idle at?
Yeah, that is a whole kit. To answer your first question, get the FP from the schrader valve.
800 Rpm.

[kevnmcd]

I didn't need all the bells and whistles that you got so I bought this one. (http://www.toolking.com/productinfo.aspx?cid=728&productid=12887) :) Thanks for the link.

[Beer-30]

Perfect.

[Marty Gras]

It was BigKatBoat, and I told you a few times that it was the IAC. I work on all kinds of EFI, turbo and blown motors every day. That IAC problem is regular deal for guys who work with EFI every day. Since most guys don't work with it everyday, I just threw my .02 in and let it fly. I'm happy that you picked it up and fixed your problem. Hope you can help me when I need your expertise.

[Beer-30]

It was BigKatBoat, and I told you a few times that it was the IAC. I work on all kinds of EFI, turbo and blown motors every day. That IAC problem is regular deal for guys who work with EFI every day. Since most guys don't work with it everyday, I just threw my .02 in and let it fly. I'm happy that you picked it up and fixed your problem. Hope you can help me when I need your expertise.
Ah. Yeah, I was figuring IAC all the time. Especially after checking the fuel system/pressure and not finding any up/down. I was just hoping it was only the IAC and not the IAC controller in the ECM.
I had to ask myself what it was wanting. 3/4" forward off of idle with the throttle was giving it the AIR that it needed. Therefore, it had to be what was controlling the idle air into the motor.
I forgot about your input, because I think you and I were the only ones focussing on that. Some others said they didn't think it was the IAC. That's what worried me about the ECM.
Another thing cool about the parts is; I found them at Marine Power for 1/4 less than Merc wanted. Good idea on listing them.
I may be running other stuff by you, since you work with EFIs. I am getting ready to setup 3 EFIs. All Holley Commander 950s - but;
1- 700 throttle body on a 312 Ford Y-block stroked to 346.
1- StealthRam MPI on a worked 339 (327 = .060) with TrickFlow heads.
And, possibly a 2X4 TBI setup on a stroked 409 W-motor.

[Marty Gras]

How late of an 'updated version' are you using? The Holley stuff that I have seen, we quickly replaced with Digital, Haltech, or Electromotive. The Holley stuff just didn't stay "set" and needed constant 'tweeking'. I do know that Edelbrock and a few others are using Merc/GM stuff from Motron and it is really nice.

[Beer-30]

How late of an 'updated version' are you using? The Holley stuff that I have seen, we quickly replaced with Digital, Haltech, or Electromotive. The Holley stuff just didn't stay "set" and needed constant 'tweeking'. I do know that Edelbrock and a few others are using Merc/GM stuff from Motron and it is really nice.
Well, this is the latest stuff. Just got the first two units, and they are their latest digital ECMs. The first "ProJection"s were trash. These are said to be as good as the Accel DFIs. They are laptop programmable instead of their analog "dial box" of the past. We'll see.

[Marty Gras]

PS, "IAC counts" is the signal the ECM is sending to the IAC motor to keep the engine in it's proper idle speed range. If you have "high counts" you would be above 10, "low counts" 4 to 9, "normal counts" under 3. If the IAC is being told to move "high counts" or "low counts" it means that there is some other problem (mechanical/ electrical) being compensated for by the IAC motor. The mechanical operation of the IAC will not produce any codes. The idle speed being wrong, (too high, too low) the engine stalling, or the ECM not sending a signal to the ECM will 'throw a code'. Merc has followed the basic GM thought process and improved on it for the marine environment. That being said, it's not fool-proof, and what you see is not always what you get. The "first idle speed control" on the Merc 555 system is the 'spark timing', not the IAC. The IAC comes into play AFTER the spark timing has made a number of adjustments for idle speed/ runability.

[Dave_N]

The PCM555 system does not display IAC position as "counts". It uses a Ford Pulse Width Modulated IAC motor, and is displayed as a percentage (duty cycle). 0 percent being closed and 100% being fully open. Every IAC failure I have seen on any ECM/PCM555 system has generated a fault code.
The earlier MEFI controllers use counts, counts being the number of steps (determined by a precise rotation of the armeture) the IAC motor (GM stepper motor) has lifted the pintle off the seat. Also, the GM stepper motor system will display counts of 0 to 150, not 0 to 10.
Dave

[Beer-30]

Well, I can tell you that it didn't set a code. I never saw what the percentage was, as the last time I had it scanned, it was idling fine. It had done the hi/lo idle thing a few random times, but not consistantly. There was never a beep from ECM during all of this crap.
I know there are several peeps out there that don't care for ECM stuff and still dig carburetors. Personally, I would work on an ECM/EFI every week if I had to just to have the precision of its delivery. The few carbed classics I have just don't run near as efficiently. But that will be remedied.
Thanks for the input, guys.

[Marty Gras]

"Dave" on the Merc DDT (chip#1.31) and computer that I use the 555 system 'Data Monitor', shows IAC % (or position), and IAC 'counts'. Two separate lines of data. The counts are/do change, and they indicate the IAC's activity range. When the 'counts' (IAC range) is doing a lot of traveling while idling out of gear (no load) Mercury Marine and I have found that this indicates an electrical or mechanical problem and the IAC/ECM are trying to compensate a rough or unstable idle by continuous corrections that are out of the normal idle 'range/%' for the IAC and the signal sent to it. Also, if the ECM sends a signal to the IAC, and the IAC does not phyiscally respond to the signal, there will BE NO CODE. The ECM will just keep sending a higher 'range/%' signal, the IAC will still be unresponsive and the motor will idle slowly and often stall,(or the converse and the motor idles way too high and the IAC won't slow it down) NO CODE IS SET BY THE IAC. (the stalled motor may set a code, but not IAC) The DDT or any other compatable test equipment are reporting the signal SENT TO THE IAC, not the actual IAC activity, nor the function of the IAC, just the signal sent to it. As far as the "0 to 100" deal, GM calls it 'counts' and Ford calls each 'position of movement' a % of duty cycle. It's all a measure of movement and the precise way each measures it. BUT the Merc test equipment that I use calls it 'position/%' for it's normal operating area, and 'counts' while measuring instant activity durring testing.

[Marty Gras]

Oh, I get your question about the "0 to 10 thing". What I was trying to say is that a normal IAC 'reading' at idle (no load) would stay within 0 to 3 increments of change. (Example; a 5.7 idles around 30%(counts), (if the throttle plate setting is as from the factory) and it would be idling (no load) at normal temp between 27 and 33. If the numbers got out to the 26- to 34+, you would be feeling the motor idle going up and down, and read the spark timing going all over the place. If the numbers went way out to 20- to 40+, you would have a very unstable idle speed. (surging like a too rich blown motor). Yes, no IAC motors have such a small (ten count) range, 100 (of whatever measurement) is a normal starting point for travel increments. PS most all of the "old style GM" stepper- motor IAC's are still working fine, however, the "new and improved Ford" triple-throw down IAC motors have been nothing but problems!

[Dave_N]

Marty/BigKat,
Thanks for the clarification. I too work with (OEM marine) EFI every day. I understand what you are saying about normal IAC position/duty cyle being pretty stable at idle, and it may be true on the small block (ECM555) applications, but not on PCM555/496 engines.
Normal IAC activity on a 496 at idle will be very different. It will rapidly change up and down by ten or more percent each way (20% swing). Maybe Beer30 can tell us what his new IAC is doing at idle.
I use Diacom software, not the Merc DDT, and I don't have a seperate "counts" data field, just the one called "IAC Duty Cycle". Maybe I am missing something.
The last thing I will still disagree on is that a stuck IAC will not trigger a fault code. Personal expierience and the Merc service manual say otherwise. Maybe not in all cases, but in every one I have seen.
Dave

[kevnmcd]

Dave N - I see you are from NB, where do you work? I just did a rebuild on my 502 EFI and need someone to help me with reducing my idle down a little. Currently it idles at 800 and I would like to get it down to around 600 or so but I can't do it without getting into the ECU. Just wondering if you could help me out or know who could. Thanks.

[Dave_N]

Kevin,
I work for myself. I would be more than happy to help you figure out what to do about your problem. Where is the boat located?
Dave

[kevnmcd]

Kevin,
I work for myself. I would be more than happy to help you figure out what to do about your problem. Where is the boat located?
Dave
Dave - The boat is stored down south but I can bring it up here (Mission Viejo area) anytime. I will be bringing up this way in a couple of weeks to get it ready for a lake trip.
Do you have a shop or work out of your house? I believe all I need to do is hook it up to a computer and reset the idle rpm setting. Can I do this any other way?

[Beer-30]

Ok, for anyone that experiences the surging idle or other idle problem related to the IAC valve, here are the part numbers that I used:
I looked the parts up on Mercury Marine, but after a Google search of the part number(s), I found Marine Power. They had the items at a significant discount.
Idle Air Valve: 862998
Gasket for same: 27-863112
Merc listed them for $88.25 and $1.10 - respectively.
Marine Power had them for $62.88 and $0.68. I see, however, that the prices have gone up on Marine Power. They are now similar to Merc's.
http://www.marinepowerservice.com/

[Beer-30]

Ok, scratch that last post.
After a few outings, in started surging again. Still sooty on the transom. Decided to take it to pro's.
Dropped it off yesterday AM. Told service writer what it was doing and what I had replaced. He said it sounded like TPS. I told him I had checked that BEFORE it had started surging and it was showing perfect voltage ranges.
The service writer calls me today, and said his thought was confirmed. TPS has gotten "sticky", probably a broken internal spring. At idle, it was showing in the high 3 volt range. So, the ECM was sending fuel and spark for 60-70% throttle. I had told him it was fine after I had changed the IAC, but started again. We figure it was because I had removed the clean air hose to the IAC from the throttle body - all the commotion had shaken it to return to idle position. After a few more runs, it stuck again. New one ordered. Now it's on them if it happens again.
Had them service the sea-pump while waiting for the part.
We'll see if new TPS / adjustment lowers the soot output.
If I had bought an ECM reader at $350, I would have found it. New TPS is about $90. The writer told me the TPS portion - including labor was $320. PLUS, I put the new IAC on at $65. I would have been money ahead by now.