2000 Mercruiser 5.7 Horizon MPI

G

goodtimes

Seaman
Joined
Sep 17, 2007
Messages
51
Hi Guys,

My mercruiser is runnin way to rich. Gots lots of black smoke through the exhaust. Checked the wires and firing order-looks good. Since this is a fuel injected motor I was thinking it could be from a simple sensor. I also read up on MAP and Mass-Air flow sensors and not sure which one MPI uses.

Any one have an idea what could be causing this?

Thanks
 
Don S

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: 2000 Mercruiser 5.7 Horizon MPI

About the only thing you can do is check the basics, tuneup, compression, fuel filters, etc. the follow the systamatic procedures in the manual for testing the items in the system.
Guessing and changing parts that someone else had wrong will cost a fortune and likely not find the problem. Here's the link to the OEM service manual, it's only 12.5 MB, but without it, you don't stand much of a chance of finding the problem.

http://www-alt.mercurymarine.com/mnetdata/SERVICE/CRUISER/Servmanl/24/24covr1.pdf
 
wkb2460

wkb2460

Petty Officer 2nd Class
Joined
May 4, 2008
Messages
146
Re: 2000 Mercruiser 5.7 Horizon MPI

Is your engine temperature running at 160 degrees?
a cool running engine will cause a rich condition.
 
G

goodtimes

Seaman
Joined
Sep 17, 2007
Messages
51
Re: 2000 Mercruiser 5.7 Horizon MPI

Don S said:
About the only thing you can do is check the basics, tuneup, compression, fuel filters, etc. the follow the systamatic procedures in the manual for testing the items in the system.
Guessing and changing parts that someone else had wrong will cost a fortune and likely not find the problem. Here's the link to the OEM service manual, it's only 12.5 MB, but without it, you don't stand much of a chance of finding the problem.

http://www-alt.mercurymarine.com/mnetdata/SERVICE/CRUISER/Servmanl/24/24covr1.pdf
Click to expand...


Don thanks for your help. That link was very useful.
 
G

goodtimes

Seaman
Joined
Sep 17, 2007
Messages
51
Re: 2000 Mercruiser 5.7 Horizon MPI

I took my boat to olympic boats in canoga park (closest to me and cheapest). They ran a diagnostics and it came out clean with no errors. He said he could do a leak down test on the injectors and cylinders/valves to verify there working properly. He also mentioned that it could be the ECU itself.
Could I take the boat to a automotive injector cleaner and just get the injectors cleaned to make sure the injectors are clean?

Is there a way to test the ECU? Would hate to buy a new one at $1,500.
Can't I just sent it to Mercruiser and they could flash it with new software and see if it is defective?

What would you guys do in this situation? Would hate to throw money in a black hole with these damn gas prices..


Thanks
 
R

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: 2000 Mercruiser 5.7 Horizon MPI

what would I do?
I would simply test the subsystems, the ECU has already told you whats not broke.
if the tech is using the correct stuff leaking injectors can be found by running a rail pressure drop test.
a clogged pressure regulator screen can increase fuel pressure and cause the system to run very rich.
I saw an o5 MPI volvo last summer that had 95 PSI on the rail, a quick regulator screen cleaning dropped it back to its 45PSI range and everything worked again.
careful troubleshooting by trained techs that actually understand what each part does and how it affects the system is mandatory on todays EFI motors.
 
JustJason

JustJason

Vice Admiral
Joined
Aug 27, 2007
Messages
5,321
Re: 2000 Mercruiser 5.7 Horizon MPI

goodtimes said:
Can't I just sent it to Mercruiser and they could flash it with new software and see if it is defective?
Click to expand...

ECU's are hardware driven, not software driven.

I'm with rodbolt on this one, check the fuel pressure.
 
G

goodtimes

Seaman
Joined
Sep 17, 2007
Messages
51
Re: 2000 Mercruiser 5.7 Horizon MPI

Pulled the injectors and they looked good but got them professionally cleaned anyways.

Where would the fuel pressure regulator be on the Mercruiser?


Thanks for all your help fellas..
 
Don S

Don S

Honorary Moderator Emeritus
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Messages
62,321
Re: 2000 Mercruiser 5.7 Horizon MPI

Pulled the injectors and they looked good
Click to expand...
Bad ones look no different than good ones.

but got them professionally cleaned anyways.
Click to expand...
If they weren't bad, why pay for that service. You are throwing money at the problem and hoping for the best.

Where would the fuel pressure regulator be on the Mercruiser?
Click to expand...
Earlier, I gave you the link to the OEM service manual. Have you even looked at it? If you had, you would know exactly where the regulator was and how to test it.
 
E

Ed R

Petty Officer 3rd Class
Joined
Apr 19, 2008
Messages
92
Re: 2000 Mercruiser 5.7 Horizon MPI

Er p here! your motor has a knock senser which controls spark advance, and injecter timing,though the ECU. Temp senser would control air/fuel to a point. as well as IAC valve. I raced boats over seas in 95, where fuel octane was over 97 , all of the merc EFI boats all ran very rich!!! that knock senser kept on searching for that knock! Crazy but true! A higher octane will make a motor run richer. think!
 
G

goodtimes

Seaman
Joined
Sep 17, 2007
Messages
51
Re: 2000 Mercruiser 5.7 Horizon MPI

Don S said:
Bad ones look no different than good ones.
Click to expand...
The mechanic helped me pull the injectors and put it on the machine. After all that I just told him to make sure thier clean.


Don S said:
If they weren't bad, why pay for that service. You are throwing money at the problem and hoping for the best.
Click to expand...
He didn't charge me for the cleaning just for an hour of help. With gas prices now days I wanted to maker sure I'm getting the best spray pattern..LOL

Don S said:
Earlier, I gave you the link to the OEM service manual. Have you even looked at it? If you had, you would know exactly where the regulator was and how to test it.
Click to expand...


Yes I did look at but didn't notice the section.

Thanks again for all your help. Your a wealth of info and help.
 
G

goodtimes

Seaman
Joined
Sep 17, 2007
Messages
51
Re: 2000 Mercruiser 5.7 Horizon MPI

BTW: When we first got the boat my mechanic replaced my spark plugs with NGK BPR5EFVX. It does not seem to be the correct one on the NGK site and in the service manual .

Are these cooler plugs compared to the original?

edit: That's the correct part # on the flame arrestor cover.
 
G

goodtimes

Seaman
Joined
Sep 17, 2007
Messages
51
Re: 2000 Mercruiser 5.7 Horizon MPI

Anyone have a good/inexpensive source for injectors? Accidentally broke the plastic plug part. :mad:
 
G

goodtimes

Seaman
Joined
Sep 17, 2007
Messages
51
Re: 2000 Mercruiser 5.7 Horizon MPI

I might have found the problem.. The vacuum hose that goes to the fuel regulator was stuck underneath the coil mount cutting all vacuum pressure. Hope this it. Will test this weekend..
 
JustJason

JustJason

Vice Admiral
Joined
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Messages
5,321
Re: 2000 Mercruiser 5.7 Horizon MPI

if you checked your fuel pressure like rodbolt and i told ya to 2 weeks ago you would have found that alot sooner....
 
G

goodtimes

Seaman
Joined
Sep 17, 2007
Messages
51
Re: 2000 Mercruiser 5.7 Horizon MPI

captJason said:
if you checked your fuel pressure like rodbolt and i told ya to 2 weeks ago you would have found that alot sooner....
Click to expand...

When I took it in to get diagnosed, my mechanic said he checked the fuel pressure and everything was up to specs. I guess he didn't...
 
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