575sci issues
 

Who is the resident 575 expert on here? I have a 2002 29 Fever/575 that I am having trouble figuring out some issues.

Expert ? he got banned........post up the issues you are experiencing

I developed an issue last season with startup. cold/hot, didn't matter, when starting it would crank over, a few cylinders would fire, then just crank crank crank.....until i raised the throttle lever to about 20-30% and then it would backfire and stumble to life. I attributed it to possibly a faulty injector(s) after reading numerous posts and talking with Eddie Young. After debating on rebuilding the stock injectors I decided to go with Eddie's injector plate update. After install, cold startup is good, however it seems extremely rich at idle.....now to my current problem.....when coming off of idle, raising the throttle to accelerate, at aprox 1200+- rpm the engine coughs and dies. ( i believe it is a lean cough). After talking with Eddie and pulling codes (21 TPS v high;23 MAT sensor v high;34 MAP V low) we thought the TPS could be the issue, To verify an issue I filmed the throttle blades movement while watching the scan tool and advancing the throttle lever.....sure enough the TPS was not sensing % until I would get to about 15-20% throttle and then it would start counting......replace TPS and MAP sensors....cleared codes....1st time out ran great (still rich at idle) but no lean cough.......I thought great problem solved......2nd time out, long idle through no wake and waiting for oil temp to rise.....go to take off and.......1200 rpm cough and die again.....having to raise throttle again to startup, small backfire and stumble to life again.....3 times in a row.....the 3rd time i raised the throttle to 3000 and let it run for about 45 seconds.....brought back to idle and accelerate without issue.
Once running and on plane the boat has never run better....smooth, max rpm, zero issues once past the "cough"
I did not replace the "MAT" sensor, not sure if that could have any effect on the situation but after clearing the codes and being out several times now none of the original codes have returned
Towards the end of the last test ride we were cruising at 3500 and started advancing the throttle to 4000 and I noticed the alarm going off....quickly shut down, scanned the codes and had a code 43 ESC detects constant knock stored.....cleared the code, started back up (with no issues) and took back off with no lean cough.....alarm stayed off the remainder of the trip.....

SO at this point, I am beyond frustrated on where to go next, I am going to go back to the TPS and see if it is picking up throttle input when I start to move the throttle lever and go from there.....

here is a video of the issue (hopefully the link works for you).
https://www.icloud.com/photos/#043X8...1tp1dsiVXBrRHA

Have you done anything with the IAC pulled and cleaned or replaced ?

Yes, I replaced the IAC with a factory Merc before I did the Eddie Young upgrade. I believe the original was working as there was no change from old to new.

Have you checked the distributor cap and rotor? Those GM EST caps and rotors will barely make it a season before corroding up badly.

Yes, I have put a new cap and rotor on several times, plugs every 20 hours, replaced the module underneath the cap, wires are about 100 hours, however, I will inspect....again. Not ruling out anything at this point. THX

Have you checked the timing ? stock tune on a stock engine ? Im not sure if Eddies TB mod's require a remap

I checked the timing at idle, but I can check it again. Running Eddies' tune for his plate for a stock engine. The lean cough started after installing his plate. Eddie is saying its the same tune he has used on lots of other 575s without issue.

is there a possible vacuum leak

possibly, I am not going to rule out anything, not sure how to check that.

not working for me

works for me SB, just off idle 1000,1100 revs pops and dies.................whats happens if you throttle up faster

Fuel psi correct ?
ecu and all other electrical grounds good ?
charging and battery systems ?

fuel pressure on the dash gauge seems fine, same as before the plate but I did need to install a fitting to adapt the sensor to the plate. I have not hooked a gauge in-line. I will look over the grounds.....batteries are less than two years old and charging system seems good but I can check alt output.

hmmm. Tried again. I get this on my phone.
(thanks for description of what happens in vid) :thumbs


https://cimg0.ibsrv.net/gimg/www.off...66d5a80b1b.png

IF I just smash through that spot it does not stall. Not ideal as I was always taught to take off easy to help protect the drive. I am more concerned with maneuvering and needing to throttle up a bit during docking etc

I know our engines are different but I had a similar issue with one of my whipple engines turned out to the the iac and mine had no codes, I know you replaced yours, you can pull the iac out leave it connected to the harness and cycle the key on and off and see if you get full travel on the motor, mine would only go half way and stop. to test for a vac leak with the engine at idle spray a bit of carb cleaner around the intake where the TB's mount, if you hear the idle speed up there is a leak

Just thought of something else that seems strange, when I am scrolling through the scan tool there is a MAT sensor reading (last night it was reading -34 deg F) but i do not think the 575 has a MAT sensor? Could this be an issue?

also the first time I pulled the codes there was a code 21 TPS voltage high, code 23 MAT sensor voltage high, and code 34 map sensor voltage low....as stated I have replaced the TPS and MAP but have not done anything with the "MAT" as I do not know where or if it even has one. Cant locate one on the parts diagram either

I took this video last night while watching the TPS % on the scan tool. The throttle lever moves quite a bit before the TPS is picking up %. It seems the approximate location where the tps starts to read is where the cough/stall happens....again hope the link works https://share.icloud.com/photos/0eb29Ou-YYVKnY2O7GcbNgOuw

2nd video is blade moving well before tps is picking anything up.
https://share.icloud.com/photos/08cNM9GdfZUCc5wZ08jPLPzzw

just watched the vid, is the throttle cable adjusted correctly

I believe it is, the throttle blades start moving and the motor RPM raises from idle to around 1100 (like in the first video). Is there an adjustment procedure for the cable that I can verify?

I just make sure there is no play, that engine should idle around 750-800 ?

Is the tbodies linkage moving when the throttle lever is while the tps not changing voltage yet.

Does your scanner show sensor volts or just % ?
Tps should change volt value for any throttle body linkage movement.

OP have a manual ? If not, does anyone ? What does the section on tps say for it’s specs and diagnostics.

Yes the scanner reads both. I will try and get a video of the linkage moving while reading voltage and %.
I do have the service manual but not the "Diag" supplement. I looked through the manual and it just has replacement procedure not testing of TPS.

yes it idles around 750-800.

maybe you have the IAT not the MAT ?

https://www.boats.net/product/mercur...01c6b76178631f

Yes, it def has an IAT in the flame arrestor.
The weird part is the scanner is reading Manifold Air Temp....

My wooples :D have a MAT sensor in the rear of the lower intake plenum...........Eddie would know for sure

IAT/MAT are one and the same on these mefi engines fwiw

Thanks for that info on the IAT.
I pulled the linkage off at the TB and watched the scan tool while manually opening the throttle blades. TPS voltage at idle was .54V and started increasing immediately, but would raise to .84V before the TPS % started to climb off "0"...Not sure if this is significant or not.....?
Looked over wiring and connections for TPS, MAP, IAT; checked the distributor cap and rotor for corrosion; checked the vacuum lines for cracking or kinking etc,

Next steps?
I am going to plumb in a mechanical fuel pressure gauge and closely watch that....looking for other ideas here. Summer is coming and I am getting frustrated lol.