Mercury EFI 150 SURGE

[EuropeanAM]

Does the pressure drop to 25 psi the moment you gun it, or does is drop gradually?

Pressure regulators aren't normally "intermittent". Much more likely that you have a supply problem or a pump problem.

[darrall]

Does the pressure drop to 25 psi the moment you gun it, or does is drop gradually?

Pressure regulators aren't normally "intermittent". Much more likely that you have a supply problem or a pump problem.

It was a constant 25psi from the moment I started it. It didn't even move when I gunned it to try and get it out of the hole.
But even the time before this when I ran it and had 25psi, it would get up and move. Now it won't do that.
Tach was also jumping around at idle. when I gave it gas it would stop jumping.
It's weird though that I had 35psi running it on the ears before I put it in the water.

Thanks,
Darrall

[kmelford]

Don and Joe - I've been tracking all the EFI issues on the older Mercury outboards including a couple of threads of my own. It seems a lot of time is spent running a similar course checking fuel, electrical and control items. Many things get addressed and it usually doesn't solve the problem or it ends up leading to the ECM which is expensive ($800 to $1500). In your experience, how often is it the ECM based on age (These engines are 20+ years old).

Thank you for any insight or feedback you are willing to share on this.

[EuropeanAM]

In MOST cases, the ECM is intermittent (ie: A driver works one minute, doesn't work the next). Caused by loose drivers on the circuit board of the ECU.

Unusual for them to act this way (but it's obviously not impossible).

In this case- he could check the fuel pump voltage and reference it to the Service Manual based on engine RPM's.

Darrall: Checked the Voltage Regulators?

[darrall]

In MOST cases, the ECM is intermittent (ie: A driver works one minute, doesn't work the next). Caused by loose drivers on the circuit board of the ECU.

Unusual for them to act this way (but it's obviously not impossible).

In this case- he could check the fuel pump voltage and reference it to the Service Manual based on engine RPM's.

Darrall: Checked the Voltage Regulators?

I haven't checked the voltage regulators. They were replaced about 10 years ago.
I'll take the plate off this weekend so I can get a good look at them & see if I see any burning.
Would reading the voltage on my fish finder help any?

[JOE54]

Don and Joe - I've been tracking all the EFI issues on the older Mercury outboards including a couple of threads of my own. It seems a lot of time is spent running a similar course checking fuel, electrical and control items. Many things get addressed and it usually doesn't solve the problem or it ends up leading to the ECM which is expensive ($800 to $1500). In your experience, how often is it the ECM based on age (These engines are 20+ years old).

Thank you for any insight or feedback you are willing to share on this.

varies , ypou sure it has spark on all 6 when problem occurs ??? would be nice to know which cyls arent working

[darrall]

varies , ypou sure it has spark on all 6 when problem occurs ??? would be nice to know which cyls arent working

I will check spark this weekend.

[JOE54]

while im deer hunting

[EuropeanAM]

And to answer your question about Voltage: No. Voltage readings should be taken with a DVOM (at the battery, unless specified otherwise for a specific test).

[darrall]

while im deer hunting

I will be on Saturday. Good luck!

[darrall]

And to answer your question about Voltage: No. Voltage readings should be taken with a DVOM (at the battery, unless specified otherwise for a specific test).

Last time the regulators acted up I could watch the voltage on the fishfinder go up until the motor would shut down do to high voltage. That's why I asked.
Thanks

[EuropeanAM]

That is only one of several possible failure modes.

[darrall]

That is only one of several possible failure modes.

[darrall]

Checked spark on all the plugs and they were good.

[kmelford]

Darrall - thank you for keeping us up to date as you try and figure this out. I have a 96 175 EFI and chasing some similar issues. I will continue to do the same on my other threads the best that I can. I would take mine into a shop but they are extremely busy and backed up until mid November. My next step is to test and/or replace the Intake Air Temp sensor.

I appreciate having this forum especially with Don and Joe's guidance and leadership!!!

[darrall]

Darrall - thank you for keeping us up to date as you try and figure this out. I have a 96 175 EFI and chasing some similar issues. I will continue to do the same on my other threads the best that I can. I would take mine into a shop but they are extremely busy and backed up until mid November. My next step is to test and/or replace the Intake Air Temp sensor.

I appreciate having this forum especially with Don and Joe's guidance and leadership!!!

I think my next step is fuel lines & new fuel pump. I already know my fuel pressure is low. It's definitely a pain to figure out.

[kmelford]

Fuel pump in the VST or the pulse pump?

[darrall]

Fuel pump in the VST or the pulse pump?

VST, already did the pulse pump when this started.

[kmelford]

Darrall, Just following up. My issue ended up being a lack of spark in two cylinders and needed to replace the trigger. Boat is now starting and running.

Good luck with your search. I know how frustrating this can be.

[darrall]

I called my local marine shop today. They said the manual states 20 - 30 psi at the pump is recommended. What's correct, the 35psi that's been posted or what they are telling me?
I'm constant 25psi. Idle is fine. Totally bogs down when I try and get it out of the hole & runs rough. I don't want to replace something that isn't needed.

Thanks,
Darrall