Mercruiser ECM replacement?

[Ferrarakias]

Hello to everyone,
New to this forum, proud owner of a Chris Craft Scorpion 210 with a mercruiser 350. After testing, I was told by my mechanic that I need a new ECM (motor is a MCM 5.7L EFI). He replaced my original ecm (delco model 16234539) with another he had in his shop (delco model 16189069) just to have it in the water during the summer. Unfortunately the engine won't rev past 2500 rpm and the boat isn't useable.
With some research that I have done, only used ones can be found on eBay. My question for you experts is will a same model ecm be compatible with my engine? Are there any other options available (re program the original)?
Attached pictures of my engine and ecm.
Many thanks in advance and Merry Christmas to us all!
Kostas

 

[alldodge]

Thanks for the serial number, your ECM is a MEFI-1

I'm finding the 16234539 (you old one) is for a 454 TBI
The 16189069 is for a 5.7 TBI

There was 3 different mefi units for the serial number range
Flat tapped motor
Roller cam motor
LX motor

Using the other mefi and only getting 2500 rpm would need to start with the basics first.
Compression test
Check plugs and note color of them
Check firing order
Cap and rotor
See if distributor is advancing

Then check for codes using a resistor LED or a volt meter with a tone when voltage is present on the DLC connector

 

[Ferrarakias]

Alldodge thank you for your answer.
From what I can understand you're suggesting that the engine had an incorrect ecm installed. I cannot argue with this, as I purchased the boat/engine after 15-20 years of storage.
Attached a printscreen of the ecm listed on mercury marine parts catalog (part numbers 807650t2, 861078t1, 806720t7) for my serial number. Do you know which delco ecm is it?
I have checked plugs, compression and firing order, replaced distributor with a new one. I don't know what cap and rotor means!
Kind regards,
Kostas

 

[kenny nunez]

Correct me if I am wrong but what if the switch which is on the shift linkage that certifies that the drive is fully in gear is not closing wouldn’t that also prevent the engine from full RPM? I also realize that the engine may just be in protection mode.

 

[alldodge]

cap and rotor is distributor cap and rotor is the rotor button under the cap. You replaced the distributor so will assume the cap and rotor was also replaced
https://www.mercruiserparts.com/808483t3-cap-distributor

If the boat is a 1996 or 97 I would think it should be 861078T1 for the roller cam. Maybe @achris could look up your serial number and verify

Timing is set by putting the motor in base timing mode (BTM). BTM is done by using a jumper or paper clip connected to pins A and B on the DLC connector (pic above). With motor idling at spec, adjust timing

Kenny the in gear selector switch is not part of the MEFI-1, if that's what your talking about

 

[kenny nunez]

Thanks AD, it is getting to a point that if owner’s cannot get a replacement ECMs more and more of these engines will have to convert to a carburetor/ distributor.

 

[achris]

Thanks AD, it is getting to a point that if owner’s cannot get a replacement ECMs more and more of these engines will have to convert to a carburetor/ distributor.

That should NEVER be an option. That is such retarded, backward step I don't even know where to begin!

...If the boat is a 1996 or 97 I would think it should be 861078T1 for the roller cam. Maybe @achris could look up your serial number and verify...

Not from the serial number alone, need to have the block code.

Correct me if I am wrong...

You are wrong

but what if the switch which is on the shift linkage that certifies that the drive is fully in gear is not closing wouldn’t that also prevent the engine from full RPM? I also realize that the engine may just be in protection mode.

There is no 'in gear' switch on these systems. It's (as already pointed out) MEFI-1, not ECM-555 or PCM-555...

...With some research that I have done, only used ones can be found on eBay. My question for you experts is will a same model ecm be compatible with my engine? Are there any other options available (re program the original)?...

Try these guys...

OBD Diagnostics

mefiburn.com

Chris.....

 

[alldodge]

Chris I really need to stop calling you in for comment because you can really be a back side. No one needs to be degraded/put down for making a comment.

Asked so the serial number could be looked up to see what is in Mercs data base, but if you actually cannot do this anymore please advise

 

[nola mike]

Seems that these no longer supported, limited run merc special EFI systems, when they break, are far more trouble to repair/diagnose than a simple carb. I'd love to see a marinized but otherwise off the shelf gm system in there instead.

 

[Tail_Gunner]

That should NEVER be an option. That is such retarded, backward step I don't even know where to begin!

Not from the serial number alone, need to have the block code.
View attachment 354119

You are wrong

There is no 'in gear' switch on these systems. It's (as already pointed out) MEFI-1, not ECM-555 or PCM-555...

Try these guys...

OBD Diagnostics

mefiburn.com

Chris.....

Geez feeling a smidge crabby are we? Remember not to many people have your working knowledge of marine efi...and then there is the availability of the correct injectors and the cost.

Resurrecting a old Slobber Body can be quite romantic to a highly skilled marine guy. But a rather arguious task for many not so skilled. Not to mention the costs involved. Ohh did I mention cost?

 

[kenny nunez]

Fuel injection is the best thing going for automobiles. I have a 1967 Ford XL that was a 390, I installed a 32 valve fuel injected 4.6 from a 98 Lincoln MK8 that was water damaged and converted it to a Mustang Cobra format doing all the wiring, plumbing, hydraulics and using all engine emission controls except for the catalytic converters. T45 transmission, 4 wheel disc brakes with Hydro Boost. 32 k miles and not one problem. Long Hauler on the Hot Rod Power Tours.
Also a 68 Ford F 100 that I am the original owner of, installed a Mustang 5.0 Coyote crate engine doing all the welding, wiring, plumbing, and using a 04 front clip from a Crown Victoria with Hydro Boost for the 4 wheel disc brakes.
This is a boat forum but no matter what it is the mechanical and technical abilities needed are the same.
Merry Christmas Chris.

 

[achris]

Chris I really need to stop calling you in for comment because you can really be a back side. No one needs to be degraded/put down for making a comment.

It's just this one guy, he puts out so much rubbish it's disturbing.

Asked so the serial number could be looked up to see what is in Mercs data base, but if you actually cannot do this anymore please advise

Just from the serial number it's not possible to see if it's a flat or roller cam. I can get everything else, but not that info. Need the block code or a physical inspection.

Chris...

 

[Ferrarakias]

It's just this one guy, he puts out so much rubbish it's disturbing.

Just from the serial number it's not possible to see if it's a flat or roller cam. I can get everything else, but not that info. Need the block code or a physical inspection.

Chris...

Thank you all for the comments.
Dear Chris,
Don't have the serial number you ask, but will go and check it out tomorrow. Only found the attached picture that I took prior washing the engine.
Bought the boat/engine 2 years ago, had the whole thing taken apart for restoration, I worked on the boat and took the engine assembly to a friend mechanic. He replaced oil filter, oil, spark plugs, gas pump, both throttle body injectors, etc and finally got the engine running. When the boat was finished we had the engine installed and tested in the water. Unfortunately the engine couldn't rev full rpm and due to the boat's weight no travelling was possible. He then replaced the ecm with another (as stated in my first post) worked better (max rev 3200 though) and was able to stay afloat the sea level (please excuse my bad English). Unfortunately it only last one ride, then same problem happened again. Haven't been able to sort it out since.
Cheers to all,
Kostas

 

[alldodge]

If you find the block casting number it can be looked up at mortec.com

 

[kenny nunez]

Just a question, has the fuel tank ever been by-passed with an outboard 6 gallon outboard tank?

 

[Tail_Gunner]

Just a few thoughts.
1. Can you rev the motor up to 3500/4000 rpm with no drive engagement? Beware just a slow very short burst...think in seconds of time..like 2.

2.You replaced your injectors? What are the model numbers?

3. I have to ask...your prop pitch? Say 17?

4. I assumed this engine was a throttle body...Perhaps it might be a MPI?

Below is a link to a very skilled/reputable vendor. His number is in the post. He is quite capable of a reflash

OBD Diagnostics

mefiburn.com

 

[Lou C]

Wow the restoration really looks great nice job on a classic Chris Craft!
Hopefully you can work thru the ECM issue.
As far as EFI vs carbs, I’m not an expert but I will quote someone who is….
Cliff Ruggles of Cliff’s High Performance Quadrajets….
“We can build a Quadrajet that runs like its fuel injected”
He’s very well respected in the auto restoration business in the USA and does a lot of marine work. I’ve read his book and used his rebuild kits and other parts and my old boat with the QJet runs better than it ever has….
If you can get a rebuilt ECM that’s right for the engine then great just keep it that way; but if you’re can’t, there ARE alternatives! Long live the US aftermarket!
Merry Christmas to all!

 

[Lou C]

PS
Our last carbed car was a 1975 Olds Delta 88 with the 5.7 V8 with the Quadrajet. This had GM’s HEI system and the 1st use of cat converters. It ran a lot better than our 1972 Chevy Impala with the 5.7 & Rochester 2bbl carb & points ignition. With the QJet we never had to rebuild it running on straight gas and we had that car 15 years.
Yes in general EFI is more reliable but repair is easier and far cheaper with carbs no one can really dispute that.
Not that it matters but that boat looks old enough that it almost certainly had a carb on the original engine, it looks to be mid to late 80s vintage, so the original engine most likely DID have a Quadrajet which Merc used until approx '90 or so.

 

[Ferrarakias]

Just a few thoughts.
1. Can you rev the motor up to 3500/4000 rpm with no drive engagement? Beware just a slow very short burst...think in seconds of time..like 2.

2.You replaced your injectors? What are the model numbers?

3. I have to ask...your prop pitch? Say 17?

4. I assumed this engine was a throttle body...Perhaps it might be a MPI?

Below is a link to a very skilled/reputable vendor. His number is in the post. He is quite capable of a reflash

OBD Diagnostics

mefiburn.com

Tail_gunner,
1. Yes the motor revs higher when in neutral.
2. Original Model number 17086237 GM Rochester 0x55, I bought a pair of remanufactured ones from eBay as the oem were way too expensive!
3. Don't have a clue! I used the propeller that came with the boat when purchased.
4. How can I help identifying what it is? Send some more pictures of the carb?
Many thanks,
Kostas

 

[Ferrarakias]

Just a question, has the fuel tank ever been by-passed with an outboard 6 gallon outboard tank?

Kenny nunez,
Yes, already tried that!
Kostas