2002 Mercruiser 5.0 MPI rich Condition

cedarridgeco11

Recruit
Joined
Jul 6, 2022
Messages
5
Hey everyone, I picked up a Stingray boat a few months ago, and have had my first BOAT issue.

So I have searched and found many conditions similar but have not found my resolution yet...

First off my serial number is 0M329027.

Background of Issue: I am have a rich running engine. At first it seemed to only happen when switching gears but now it is stalling at idle and is hard to start. Compression is fine, fuel pressure is 35-38 typically, I have read 43 is where it should be. When I purchased the boat, it started up great. I replaced the outdrive and have had the boat out and use on weekends. Recently the initial cold start up and idle has been poor.

Items I have Tried:
Ran 2 tanks of treated fuel through (Seafoam first tank, Lucas second tank)
Replaced the IAC - no change
Replaced all spark plugs - All plugs appeared OK except for black soot, which matches the rich condition theory
Replaced all spark plug wires.
Replaced fuel regulator
Removed AIC Muffler filter

The Engine still starts hard. In order for me to get the engine cranked, I have to knock it into neutral and rev the engine up, let is run for 5 minutes or so and then it shifts forward and reverse perfectly fine. I think the only thing that has really improved the stalling and idling issue is indeed the AIC Muffler filter. It definitely needed replacing. The engine accelerates flawlessly and will run 54mph at 5500 RPMs. Idling RPMS seems to be around 8-1000.

Right now I have injectors on order, my assumption is since they are 20 years old, I may as well replace them anyways. But want to make sure that i am chasing down the right repair...

Any ideas? Hope I got you all the correct information. Thanks!
 

cedarridgeco11

Recruit
Joined
Jul 6, 2022
Messages
5
Hey everyone, I picked up a Stingray boat a few months ago, and have had my first BOAT issue.

So I have searched and found many conditions similar but have not found my resolution yet...

First off my serial number is 0M329027.

Background of Issue: I am have a rich running engine. At first it seemed to only happen when switching gears but now it is stalling at idle and is hard to start. Compression is fine, fuel pressure is 35-38 typically, I have read 43 is where it should be. When I purchased the boat, it started up great. I replaced the outdrive and have had the boat out and use on weekends. Recently the initial cold start up and idle has been poor.

Items I have Tried:
Ran 2 tanks of treated fuel through (Seafoam first tank, Lucas second tank)
Replaced the IAC - no change
Replaced all spark plugs - All plugs appeared OK except for black soot, which matches the rich condition theory
Replaced all spark plug wires.
Replaced fuel regulator
Removed AIC Muffler filter

The Engine still starts hard. In order for me to get the engine cranked, I have to knock it into neutral and rev the engine up, let is run for 5 minutes or so and then it shifts forward and reverse perfectly fine. I think the only thing that has really improved the stalling and idling issue is indeed the AIC Muffler filter. It definitely needed replacing. The engine accelerates flawlessly and will run 54mph at 5500 RPMs. Idling RPMS seems to be around 8-1000.

Right now I have injectors on order, my assumption is since they are 20 years old, I may as well replace them anyways. But want to make sure that i am chasing down the right repair...

Any ideas? Hope I got you all the correct information. Thanks!
Also, one thing to add, when you remove the vaccum line at the fuel regulator, the fuel pressure goes from 38 to 43ish at idle. I thought that was ODD, since i thought the vacuum would increase the fuel consumption.

Also, I am not sure if I am running very inefficient on fuel economy, it feels to me like it sucks gas more than it should. But i usually have had outboards in my previous boat ownership.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Stop throwing parts at the engine in hope that you'll fix it. You likely won't, and you'll be out of pocket hundreds, if not thousands.

You need to have the diagnostic software hooked up to find out why the ECU is richening the mixture. It could be a failed sensor or something like that.... And if the software can't tell you what's failed, it will at least tell you what hasn't failed...

Chris...
 

dubs283

Vice Admiral
Joined
Jul 27, 2005
Messages
5,343
Would also add to chris' post about audio warning system. Is there an audio "beep" when you first turn the key switch on?
 

cedarridgeco11

Recruit
Joined
Jul 6, 2022
Messages
5
Stop throwing parts at the engine in hope that you'll fix it. You likely won't, and you'll be out of pocket hundreds, if not thousands.

You need to have the diagnostic software

hooked up to find out why the ECU is richening the mixture. It could be a failed sensor or something like that.... And if the software can't tell you what's failed, it will at least tell you what hasn't failed...

Chris...
Stop throwing parts at the engine in hope that you'll fix it. You likely won't, and you'll be out of pocket hundreds, if not thousands.

You need to have the diagnostic software hooked up to find out why the ECU is richening the mixture. It could be a failed sensor or something like that.... And if the software can't tell you what's failed, it will at least tell you what hasn't failed...

Chris..


Yes most parts to date seemed like easy fixes that either needed to be done for not knowing who really owned it before and weren’t crazy expensive and we’re easy to do. I will check around with rmechanics and see if they will charge me to scan it and give me some insight. I work on small outboards a lot and figured if maybe an easy fix.

No beeps or alarms.
 

dubs283

Vice Admiral
Joined
Jul 27, 2005
Messages
5,343
No beeps or alarms.
As in no beep at all upon key up? You should hear at least one beep at key on, engine not running. This is to allow the operator to know the audio warning system is operational. If you do not hear a beep upon key on someone may have disabled the audio warning system or it has failed.

Only reason I mention is if the system does not work you may have active faults that you don't know about due to the system being in op
 

Jmunk

Petty Officer 1st Class
Joined
Jan 31, 2007
Messages
298
My experience - if your replacing the injectors with non-OEM ones I’d hold off. The offbrand ones in vehicles have caused more issues then what I’ve seen them solve.
 

cedarridgeco11

Recruit
Joined
Jul 6, 2022
Messages
5
As in no beep at all upon key up? You should hear at least one beep at key on, engine not running. This is to allow the operator to know the audio warning system is operational. If you do not hear a beep upon key on someone may have disabled the audio warning system or it has failed.

Only reason I mention is if the system does not work you may have active faults that you don't know about due to the system being in op
Sorry, yes i think it beeps once upon key turning. It also beeps when you unplug sensors like the throttle body position sensor. Gear oil got low a few weeks ago and it alarmed then too.
 

Stinnett21

Chief Petty Officer
Joined
Jun 24, 2012
Messages
608
The cap & rotor are an easy tune up for less than $100. I buy NAPA ECH RR207 cap $65 and ECH RR256 rotor $20. Requires torx bits T15 and T20. Easy job. Just don't get the plug wires screwed up.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,348
Hi. You’ve left out thee single biggest issue and cause of such a thing. The cap and rotor. Replace this and there is an extremely high chance, all will be well.
I’d also suggest that you aren’t possibly running at anything like 5500rpm. That engine won’t allow you more than about 5100/5150 before it hits the limiter. Perhaps your gauge is less accurate than the normal variance
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,348
Idle should be about 650 I’d say. Pretty sure mine runs at about 600-650 at idle.
Mine will hit the rpm limiter at almost exactly 5150 rpm at about 67mph with a 21”. A 23” will see her terrible low down power and on a rare occasion see about 68ish mph at around 4800ish rpm. But terrible mostly with that much pitch. Generally run a 20” or a 21”.
Same engine (but with cam and exhausts), on a 1400kg dry boat.
 
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