575 Sci Experts
 

Need some help with my 575 sci.Last year the blower went bye bye.Had the blower shop rebuild it (new shafts.rotors and bearings).I also installed (2) new regulators in the throttle bodies.Mercury does not sell the regulators anymore and can not give me a GM part #.I matched them up at my GM parts store.I took the boat out for a text run and it is running a little rich.When i start it i get black smoke.It ran good but,every once and awhile it pops and surges.then cleans up.Iam running a super chiller w/3 1/2" pulley,areomotive fuel pump.Fuel pressure set at 28lbs at idle.The boat never ran rich before the blower went away.Iam thinking maybe the regulators are not the right ones or maybe the iac might be bad.There was a little bit of fine shaving's from the blower around the bottom of the t.b.s and i cleaned them before install.Were do i start?Does anyone have the right GM part # for these regulators?.Thanks

Anyone?

Ask SteveZ over in the Nordic forum. He has a warmed over 575 with an innercooler that runs really strong. He is quite knowledgable, and a nice guy.

Chris

I can tell you this. Fuel pressure in the 575SCi is not
regulated in the throttle body. The fuel pressure regulator is in the housing with the high pressure fuel pump under the front of the engine. I know, I've changed the pumps before.

Mercruiserparts.com drawing at (item 15):
http://www.mercruiserparts.com/Show_...nd+Fuel+Cooler

In the normal GM TBI car systems the regulator is in the throttle body and the throttle body has a fuel inlet and outlet. They plug the outlet on the 575SCi, so I don't know whats inside or the function of what would have been the pressure regulator in the throttle body. Hope I never have to find out.

Pesky Varmint

If it's early in the season (it is) and you are running cold water through your intercooler at idle or just above idle, your motor will act very cold natured and go rich. This can be eliminated by putting an adjustable water pressure valve on the intake side of the intercooler, so that it shuts off flow at idle. Other problems are as you mentioned a bad IAC.
Re FP regulator, it is near the high pressure pump. Is your fuel pressure OK (idle and WOT?)? Maybe you installed new injectors?? You may also have a bad map sensor. They are sensitive to backfires and popping.
The throttle bodies are not very strong, just cast aluminum and therefore they are prone to leaks and breakage. Take the flame arrestor off and check them out at idle to see if you see any fuel leaks.
For spare parts and modifications, I recommend CFM TECH.
They can rebuild these for you, and they have a few performance mods too. I'll see if I can find their website for you. Here you go www.cfm-tech.com
Your avatar doesn't say where you live. If we knew maybe could recommend a good technician.
Regards,
Steve

Thanks for the info.The boat is located in lake havasu,az.I found out that i had the wrong spark plugs in the boat (thanks to my service guy).Also when i did my first test run 3 weeks ago the thermostate stuck open.It was pretty corroaded.Talking with a merc tech he told me to change out the thermostate sensor.It might be telling the computer that the motor is cool and it needs more fuel.Iam going to change out the iac's and tps.Maybe the map sensor.I still need to know if i installed the right fuel regulator in the throttle bodies.There is one on each throttle body next to the injectors.It looks like a power valve on a carb.It comes with the top housing.I called Mercury racing today and they are trying to find a GM PART # for the regulator.My intercooler is plumbed with a force fed pickup on the bottom of the boat.It does not get much water pressure at idle.I will call cfm tomarrow and see what they say.

If your thermostat was stuck, you would be rich. The way a EFI works compared to a carb is simple. When the motor starts, it reads water temperture. It adds fuel to act like a choke. When the water temperture comes up, it cuts the idle fuel back. Dont change all that stuff you have stated, fix the thermostat. See how it runs. Probally will come back to you. Those sensors dont go bad that often.

The regulator is down on the fuel pump with the cool fuel

I changed the thermostat and plugs.It cleaned up pretty good.My merc guy said to also change the thermostat sensor.It still is rich on warm start up.There are also regulators in the throttle bodies part #852955.I have aftermarket fuel pumps,no cool fuel.

I looked up what you are talking about.[imo] that part never goes out but you never know things happen.well I went to bam marine and i believe they still have one in stock, part # 852955 at $ 185.80. that is what there web site said.give it a try good luck.

I found that also.The regulator has a rubber diafram with a spring.With the great fuel we have on the west coast it ate up the rubber.Bam has one ,i need two.Mercury parts express has them online,I just need to check if they are in stock.I need to find out if the ones i picked up at my local gm parts store are the same regulator.They bolt right on.After i installed them the boat ran alittle rich.

It should be the same

If you do find out the GM part number please let us know.... It could come in handy down the road for some of us.....Thanks and good luck with the engine, hope the problem gets solved...........

These throttle bodies are off a 7.4/454 GM truck motor. Most internals are identical.
Steve

Yup, you guys are correct.

Normal 454 t-body parts will work.

The regulator in the TBI unit is deadheaded by Merc with a solid screw in plug to the return line port on the TBI. Thus, it does not control psi.

Merc uses a different regulator down near the pump, before the TBI. It does have a vacuum line that hooks up to the rear vacuum port on the tbi unit.

Pic #1 - see part#14 - this is the regulator Merc uses to regulate the fuel psi.

http://www.mercruiserparts.com/images/COMMON/26655.png

And in this pic, see part#4 which is the plug used to plug off the tbi's return line which renders it's built in regulator to be useless other than sealing off fuel of course.

http://www.mercruiserparts.com/images/COMMON/26657.png

From the pic below, it looks like these 575SC's t-bodies use the base gaskets from the 87-90 454's. So, if looking for gaskets, o-rings, regulator diaphragms, etc,etc I'd get them from local parts store for 87-90 454 truck. Say, K3500 to make parts look-up easier. Or hell, a 90 454SS pick-up truck should be know easily too. LOL.

Note: Don't assume your injectors themselves are the same as these trucks, if you are ever going to replace them. Look at the #'s stamped on the top of the injector in between the injector electrical posts, and I or anyone could probably find out for you how to get outside of $$$$Merc. LOL.

http://www.mercruiserparts.com/images/COMMON/26656.png

Myself and the local injector shop couldn't make heads
or tails out of the numbers on the injectors. I don't think
anyone can figure out what they are.

If I ever need a new injector I'll take a good one back to
him and have it flow tested at normal GM pressure (either
10 or 14 lbs I think) and then we'll know what they flow.

I don't know that number now because when he cleaned
them I had him flow them at the Merc 28 psi. For what its
worth, 6 year old injectors with 430 hours were on average
7% low on flow across the board (8 injectors).

There is going to come a day when any 575SCi owner is
just going to have to go to all new stuff from manifold up.

Pesky Varmint

Thanks for all the feed back.I talked with CFM and found out the same thing sb is saying.Mercury racing gave me a GM part # 17113192.That part has been gone for 6 years.The regulator i used is GM #17112399.It is for a 1992 5.3 and 7.4 GM motor.They made a 13lb and 30lb regulator.I guess it does not really matter because there is no return line and the fuel is regulated before the tpi.I would really like to find out a good # on the injectors.The # on my injector is 25170301.They are nla from merc.I did find a post from someone taht purchased some a few years back from merc and under mercs sticker on the box was a part #17113305.Still can not find out ant info on that #.I think it was a part # just for merc.Is it worth having my injectors cleaned.the motor has 250 hr on it.Iam going back out to the lake next week.Iam going to install a new thermo sensor,iac and tpi.I also found out they had the wrong spark plugs in the motor.Hopefully that will take care of my rich prob.Thanks.

merc dealers now have a way too clean injectors while on the engine I have not done it yet but I believe they could also do [TBI] engines also in the past we where always told not to clean the injectors only replace them but now they have changed there minds about that idea.FYI the shop that has the tool to do it in CA is Quality performance marine in corona 951-735-5503.If you had all those problems with the fuel system it looks like it might be worth trying to get them cleaned.wrong plugs and stuck thermostat will make it run rich,bad MAP sensor would be super rich and run real bad in many ways. [IAC] would surge up down, also you should change the IAC muffler in the T/B.I have had many boat oweners tell me the boat is more responsive on acceleration after cleaning T/B and IAC and new muffler. The [TPS] tells the [ECM] how much throttle you want by % and ECM tells other sensor how much fuel curve the engine needs.sorry if you already know about all this info I have a feeling you know a lot about your engine.good luck with it.

I'd do some more digging thru a local AC Delco dealer. 1711305 shows up on this 2008 'Emissions Control' Jobber Price Sheet.
http://66.0.3.26/Specials/AC%20Delco...ets/21A-20.pdf
Go to pg 15. Also, Price shown is near/at what TBI Injectors are sold at thru AC Delco dealers. So, maybe ???

The part#'s on the injectors is what many of us go by, but they are not the same part # on the box.

Again, so maybe you are on to something ????

BTW: I am CFM. LOL. I came to find this thread because you talked about OSO on the phone so I figured I'd check in on this thread. I'm not here much anymore. I can be found by phone during the week or at http://marineperformancetechtalk.com/forum/index.php a good amt of the time, but a little less now since it'm my extremely busy time of year.

Sorry I don't know more about the TBI's used on Merc's/Volvo's. I haven't gotten any of these tbi equipped boats (N/A nor S/C) in my hands.

Thanks for the info boat teak.Iam going to stop by turbo city in orange on monday.They have built a ton of hi flow tbi for street and marine.They also clean and flow injectors.If i have no luck there i will stop by Quality on the way home (live in temecula)I also have a lavey (27 sabre).Great boats.sb,Thanks for setting me straight about the fuel regulator in the tbi.I spent two hours at my GM part dealer yesterday pulling part #s for tbi parts (seal kits ,injectors).no luck.I think i might call AC Delco on mondat and chase the part #.It would be good to know down the road.Iam going to have mine cleaned and flowed and see how that works.Thanks again.Dave

No problem.

Thinking about the tbi regulator more, I think I'd almost want to get rid of the spring set-up and just use a plate or something solid (under the diaphragm) so that it doesn't flex (spring compressing/decompressing) and thus wear. I mean, schit (lol), all it's used for in these applications is to seal that passage. If you removed it, fuel would spray everywhere.

Or, just shimming up the spring some will take most of it's movement out. I used to do that in the old days before taking the time and $$ to make an adjustable base to be able to adjust spring psi / fuel psi - on how it is used on the GM vehicles of course.

BTW: At TC, watch out for Tom. He's okay most of the time, but when cranky can be hard to deal with. I think the injector guy's name is Rick ??? Not too sure on that, but he (injector person) seems like a nice enough guy.

SB,Thanks for the warning.I will let you know how it goes.Going to head out to Havasu next weekend to install the tbi's and change the plugs and thremo senor.If the weather is good i will run the boat and see what happens.What do you think about t.c hi flow tbi's?are they worth the $$$$$.Thanks

Well.I went over to Turbo City to ask some questions and get my injectors cleaned and flowed.I guess i caught Tom in a good mood.He gave me alot of tbi info and had my injectors flowed and cleanded in 2 hours.He told that those injectors are 350 chevy 61gph injectors.If you have to replace them,watch out.I guess some come from china and can flow 8 to 10 lbs different between them.On the regulator you can cut it with a bandsaw right before the diafram and tap a 1/4" thread and install a pipe plug.Pretty easy deal and you eliminate the diafram.I have been driving by Turbo City for over 30 years and only thought they did turbo's.He has alot of tbi stuff.I am on my way to havasu this weekend to see what happens.Hope the weather holds up.

Good luck Lakeman, and keep us posted.....

Well iam out here in havi.I put the boat back together yesterday.I thought i would start it up on the trailer w/water.I fired it up and the idle goes to 1200 and won't come down.I shut the motor off and restart and the same thing.Also the motor was popping alittle with more throttle.So i pull off the new iac's and install the old ones.I thought maybe i receive a bad one.I thought i will try it one more time and if that don;t work i will go barrow a scam tool from the boat shop at my resort.Fired it back up and it does the same thing.Then i take a look at the gauges and my temp is at 260,my oil psi is at 80.Then i look at the volt gauge and it says 4?O.k here we go.i started to check all the ground wires on the motor and found the starter motor ground was loose.Went around the motor tighting all the grounds.Fired up the boat and it runs great.Launch the boat and went out for a hour and it runs bedder then ever.I was talking with one of the boat techs in the boat shop here who has been helping me out and he said that is the first thing they teach them at school.If the volts drop the ecu will tell the motor to do some weird stuff (rich condition/popping).The last times i ran the boat the guages all read fine.I think that loose ground was my problem the hole time.So before you start replacing parts ,check them grounds.

Wow, almost the same thing happened to me in October. I was running down lake Havasu (down by the 3 big pipes on the CA side) when my starboard blower (575sci) locked up and smoked the belt off. I had the blower rebuilt by Mooneyham in upland ca. But the motor warning buzzer just kept beeping over and over and it ran pig rich. It apparently had backfired and took out the map sensor. I had the ECM reset and a new map sensor and all is well. I also had water pressure regulators installed since water pressure has been hitting 40+ since I installed new t-stats. Testing next weekend then hopefully Havasu for the poker run weekend(don't know if I want to push the boat so soon) mike

OK, the challenge is on. Every resource I have has not been able to cross these. The shop I took them to for cleaning couldn't even do it. Now I have one that doesn't work at all. Here's the numbers:

25170301-ACR
1060 GM

Pesky Varmint

good tbi info

need help with 575sci
 

i am having some sort of electrical issue causing a misfire in which is popping back through the blower, if anyone has had this issue please respond