Mercury 350 magnum problems please help

[badbowtie]

I did try blocking vac line and can not get fuel pressure above 30 just cycling key. It also is cool fuel setup and the serial number is 0k163560
I think he was going to run it to the merc repair shop this afternoon and see if they can hook a computer to it and see if there is any error codes or anything because I am pretty confused.

 

[tpenfield]

I did try blocking vac line and can not get fuel pressure above 30 just cycling key. It also is cool fuel setup and the serial number is 0k163560
I think he was going to run it to the merc repair shop this afternoon and see if they can hook a computer to it and see if there is any error codes or anything because I am pretty confused.

Keep in mind that the vac line lowers the fuel pressure during idle. The way to test the pump pressure is to block the return fuel line (not the vac line). Merc calls out for a special fitting to block the fuel return line. I know of some folks who have just clamped the return fuel line in order to check the pump pressure (of course not good for the line itself).

 

[badbowtie]

Okay it is at a local marine shop and I am not impressed with them so far. But I guess all they did yesterday was hook a fuel pressure gauge up to it and did the test and said they can get 35 cycling key and drops to 30 while running. They also called my buddy yesterday and are telling him they are pretty sure it is the ignition module under the cap and they told him they had to loosen the motor mounts to get to it because it is back up under the transom. They told him about 6 hours to do that. I replaced cap and rotor in it saturday and took me about half hour. So i told them I will replace it in there parking lot why they are gone for lunch today if have to. I also have never seen a ignition module act up normally they work or don't. Is it heard of on boats for it to make the boat run real bad. They are also supposed to hook the merc scanner up to it this morning.

 

[tpenfield]

One issue is 'who' is in charge of fixing the boat at this point . . . you or the shop. I would think that while it is in the shop's hands, they are determining what should be done. They will follow protocol and procedures outlined in the manuals and service bulletins, which can add time and cost in some cases.

I'm not sure the shop will let you work on the boat while on their premises.

I guess that is one of the dilemmas in helping out with the maintenance/repair of friend's boats, the sense of responsibility can be awkward at times. I help my friends out to some extent, but so far have steered clear of any heavy duty repair stuff, as I keep that for my own boat.

 

[alldodge]

Loosen the motor mounts means they want to pull the motor forward. While I do understand being able to see what your doing when replacing the module (unable to get your head in there) this is a bit much. I would only agree to something like that if they guarantee this will fix the issue. They won't do that either but its pretty bad to pay that amount of money and not have it fixed.

Agree with Ted they will not let you work on the boat.

So you cannot get the pressure up and they are saying it is a spark issue. I don't get it

 

[tpenfield]

It sounded like the shop tested the pressure and it was in spec (35 psi with just the ignition switch turned on) and (30 psi at idle . . . assuming the vacuum line is connected, which brings the pressure down a bit)

I guess it is a matter of understanding why the OP and the Shop are getting such different results :noidea:

My interest in this thread is that I am going to be replacing the fuel pressure regulator on my port engine (7.4L MPI) tomorrow . . .hoping to see the pressure test come within spec.

 

[scoflaw]

The test is only as good as the test equipment your using

 

[badbowtie]

The shop has the boat right know but we know a guy that works there and I could get in there and replace something on there property if need be. But I wouldn't let this shop work on anything from what I have seen. Yesterday they have replaced the module in the dist and said that didnt fix it so they swapped it back I am pretty sure they are practicing fixing something. They had the boat for 3 days and when I asked if they scanned the computer they told me there computer didnt hook to that year then at like 4:00 yesterday he said he talked to the merc tech hotline and found out they can hook the computer to it. So they havent scanned it yet and know they are saying they need to pull the motor to replace the coil in the distributor under the rotor and shied. Am I missing something because cant you remove and replace that without removing distributor. Or does it come apart after you remove bottom gear and slide center shaft up from bottom. Looks like depends what shop does this morning or tell us I guess going to go get the boat they have had it for 3 days and haven't figured out a thing.

 

[tpenfield]

Sounds like the shop wants to get some practice at removing and re-installing motors .. . . It is about $1K of an expense to do that sort of thing.

the drive has to come off, remove the motor from the mounts . . . do what you gotta do . . . then put it all back and re-align the engine and then install the outdrive.

 

[alldodge]

The module is just inside the distributor and is held in by two screws. I still don't see any reason for removing the motor to do it, As before the only reason to pull the motor is to give more room so they could see, otherwise your doing it by feel and I'm sure a phone pic could be taken to verify correct install.

 

[NHGuy]

Since you were able to do the cap & rotor they should be able to change the distributor module without moving the engine.

 

[badbowtie]

Yea I guess they did replace the module and that didn't fix it so they took it back off. Know they are saying the coil that is under the rotor button on the shaft that they have to remove distributor to do that one. They said they had 2 test to run yesterday afternoon but everything is pointing to that coil under the rotor.

 

[Pete104]

http://www.mercruiserparts.com/bam/subassembly/31776/2337/80

 

[badbowtie]

Yes part number 8 is the part they are saying they need to replace and want 6-8 hours to pull motor forward and remove distributor to replace it. I guess they have to remove the bottom gear and roll pin so they can take it all apart from the best I can tell.

 

[Pete104]

Yes part number 8 is the part they are saying they need to replace and want 6-8 hours to pull motor forward and remove distributor to replace it. I guess they have to remove the bottom gear and roll pin so they can take it all apart from the best I can tell.

What kind of boat is this engine in? Like everyone else I can't see having to pull the engine to remove the distributor.

 

[badbowtie]

97 Mariah 21 foot the distributor is up under the fiberglass but am still surprized it will not come out.

 

[Fun Times]

Depending on the room available above the distributor unit, sometimes the engine may need to come out or forward if possible should the overall length of the distributor assembly without the cap and rotor still installed not clear a section of the boat that is not reasonably disassembled.

If interested, here's a 2 part video of how to go about changing the GM Delco EST style pickup coil like you have there.
https://www.youtube.com/watch?v=K5QRK9VZwcM
https://www.youtube.com/watch?v=pjivERnPWHw
http://www.autozone.com/repairguide...TION-SYSTEM/Pick-Up-Coil/_/P-0900c1528008faaa

 

[badbowtie]

Okay well I guess we are heading to the repair shop this morning we heard last night from there helper that has no experience working on boats that they got the coil in yesterday and I guess they got it all installed and still dont run. I know my buddy is pissed know they told him they tested everything and that was bad. So I am assuming we are getting it out of there today and not sure if I am going to try to figure it out this weekend or if we are taking it to a bigger and hope better marine repair shop. I still think I got a bad fuel pump last week that I installed because I still cant get the furl pressure they call for but according the this shop that has the boat it only requires 30-35. But everywhere else I have read and been told it requires 43.

 

[tpenfield]

Sorry that you and your friend are going through this nightmare. What you are experiencing can be the issue with repair shops . . . they too are human and can be convinced the problem is one thing, only to find out that it is not. Meanwhile the repair bill adds up. The DIY approach has its challenges too, but you are not paying yourself $100/hour to do some trial and error.

Anyway, Please, Please go through the Mercruiser manual for this engine, regarding the fuel pressure. Do not rely on hearsay. I had seen/read 37-43 psi of fuel pressure for the MPI engines, but when I looked in the manual for my engine. . . the spec was 34-38 psi at the rail, and the pump should be providing more than 38 psi, but not over 60 psi. There may be an engine that spec's at 37-43 psi, but it is not my engine, and probably is not your engine, unless you can verify it in the Mercruiser manual for your engine.

Anyway, I just want to re-cap the background and symptoms of your friend's boat/engine, and advise us if things have changed as a result of all this work. . .

1) new to him boat, ran well at the sea trial, the boat is 19 years old, had sat for 5 years before he bought it. Generally, a very low hour engine for its age.

2) sometimes runs well and sometimes does not. Mostly does not.

3) when it is running poorly it does not have much power, tops out at about 3800 RPM 35 mph. When running well it goes to 5000 RPM & 60+ mph

4) some effort on the fuel system and ignition system (filters, sea foam, dist cap, rotor, module, etc.) to no avail.

5) replaced the 'cool fuel' pressure pump and fuel pressure regulator - no improvement

6) shop replaced the 'coil' which is at the base of the distributor (not the ignition coil) - no improvement. Fuel pressure checked out at 35 psi per their testing. No fault codes on the ECM.

7) Now what :noidea:

Is this pretty much correct?

Looking at all this, I still go back to thinking about the 5 year lay-up and the effect that it could (probably did) have on the fuel system. I am wondering what things look like internally within the fuel rails?

Was there any ECM (MEFI) data taken from the engine during operation? I believe it did not have any fault codes.

My hunch is that there may be some 'jelled' fuel in the fuel rail as a result of the 5 year layup. You could try to purge or even disassembly/clean the fuel rail(s).

 

[badbowtie]

You are pretty much correct the only thing that is has me still thinking is number 5 I actually gained 5psi when I replaced the pump and regulator which is when it went up to 30 psi. According to the shop when they checked for fault codes it did not show any of them. We have also spoke with another marine shop and gave them the serial number and they said there is a service bulletin on the fuel line about it splitting and and leaking. I am wondering if it is leaking and sucking air and no fuel yet. The repair shop that has the boat says they dont know anything about it when I asked them about it.