Vacuum line just hanging around

[Kodiak2359]

Iv been having trouble with a newly acquired boat surging anywhere near idle. Today I found what I think is a vacuum line just dangling at the rear of the engine. The other end goes to the T at the intake manifold and fuel regulator. Any ideas where the stray needs to be connected? It's obvious it was on something cause the end is bell shaped.

thanx
Dave

 

[Rick Stephens]

Generally, boat motors don't produce much in the way of decent vacuum. I've never seen a vacuum line on one... what motor? Year and serial number would be useful. Sounds like maybe someone stuck an automotive part on yours, although easily could be one of the many many models that I am unfamiliar with...

 

[achris]

Hi Dave,

It's very useful if you start each new thread with the engine year, model and serial number. for example, 2006 4.3 MPI, serial # 0W612345. This way, we don't have to keep asking for it, then go searching through 'reply' posts to see if it's there. Same thing if you have a drive question, year, drive model, serial number.

I did find a previous post that mentions a boat and it's year (be aware that engine years and boat years aren't always the same), but as most of the regular posters read and reply to dozens of threads, we can't always remember what each and every person has. Heck, I have to scroll back up to see my previous posts in any thread to remember what I wrote. :facepalm:

The other alternative, which as far as I'm concern is better, is to set up a signature file, much like I (and many other regulars) have done. That way, don't have to remember to put all the information in, and it's on every post, so we don't have to scroll back to the opening post to see the relevant information.

Cheers,

Chris........

 

[Kodiak2359]

Thanks all, forgot to mention it is a 5.7. It started out as a 5.0 mcm 0M656136 but got a long block change this year(not by me and not mercruiser just a new gm). I found the hose barb down by the fuel pump port side so I'm thinking it goes to the fuel regulator down low. We have no mercruiser dealers or shops or mechanics here so we do our best with the manuals. Manual says vacuum is used for fuel regulators and I think we have two (I can see the one on top of the in take). One on the main pump and one on the booster. There are no vacuum diagrams in my manual so just have to interpret text. Thanks for your replys and forum advice, much appreciated.

 

[achris]

Do you have the Merc service manual or one of the after market knee pads?

And yes, a vacuum line does go up to the intake for the fuel pressure regulator.

 

[Kodiak2359]

I think this is the manual version 90-864260001. I think it a factory manual but in pdf. My main two issues are engine surging and temp.
1. Temp was originally related to a lack of purging all or even most of the air out of the coolant system(which by the way has been changed to aftermarket, maybe to support cabin heat). I feel like I have the air/coolant issue resolved but the gauge is still reading higher than I feel it should. My dash gauge reads around the 180 mark but if I use a infrared thermometer on the thermostat housing it reads 150 at the highest. So the issue becomes you can't trouble shoot with faulty data. If I can find the installed sensor part # i can likely find a ohms chart to verify correct sensor accuracy. If accurate is correct I then need to verify if the mercruiser gauge and sensor are compatible or I can establish that the gauge is in error but relative and just put a couple of slices of red tape to define my operating parameters.
2. The engine routinely surges when dropping throttle from somewhere above 1000 rpm and drop to neutral. Once the engine is heat soaked for a few hours and then ran at lower rpm for 5 or so minutes while entering channel it will go to 1400 rpm and stay there for 45 seconds or longer when I shift to neutral. I then have to wait until it drops to 600 to shift again, not really conducive to docking maneuvers.
I have taken the IAC out and cleaned it (fairly dirty) ,installed a missing IAC muffler and now connected a free bird vacuum line. It still surges. So I now will find a new IAC as I can hear it operating as the surge happens. Perhaps it is hanging and overshooting .
I just got this boat a few weeks ago. I am still learning the systems but I have a long history with Volvo Penta small block Chevy motors. There are no alarm codes active that have sensors related to this motor. I do have a buddy with a Rinda techmate pro and we scanned it.

 

[achris]

... We have no mercruiser dealers or shops or mechanics here so we do our best with the manuals. ...

Here being, Alaska? (Kodiak is a bit of a clue. )

I think this is the manual version 90-864260001. I think it a factory manual but in pdf.

That's the right manual. You may also want the MPI diagnostics manual... Very useful...

My main two issues are engine surging and temp.
1. Temp was originally related to a lack of purging all or even most of the air out of the coolant system(which by the way has been changed to aftermarket, maybe to support cabin heat). I feel like I have the air/coolant issue resolved but the gauge is still reading higher than I feel it should. My dash gauge reads around the 180 mark but if I use a infrared thermometer on the thermostat housing it reads 150 at the highest. So the issue becomes you can't trouble shoot with faulty data. If I can find the installed sensor part # i can likely find a ohms chart to verify correct sensor accuracy. If accurate is correct I then need to verify if the mercruiser gauge and sensor are compatible or I can establish that the gauge is in error but relative and just put a couple of slices of red tape to define my operating parameters.

Dash gauges aren't calibrated accurate, just more an indication. If it's showing within 20 or 30 degrees of the actual temp, that's reasonable. The gauge sensor and the ECU sensor (known as ECT, Engine Coolant Temperature) are different. Obviously as one is analog, the other digital. They are at the base, either side of the thermostat housing...The gauge sender will have a single tan wire, the ECU (digital) has 2 wires, a yellow and a blk/pink.

2. The engine routinely surges when dropping throttle from somewhere above 1000 rpm and drop to neutral. Once the engine is heat soaked for a few hours and then ran at lower rpm for 5 or so minutes while entering channel it will go to 1400 rpm and stay there for 45 seconds or longer when I shift to neutral. I then have to wait until it drops to 600 to shift again, not really conducive to docking maneuvers.
I have taken the IAC out and cleaned it (fairly dirty) ,installed a missing IAC muffler and now connected a free bird vacuum line. It still surges. So I now will find a new IAC as I can hear it operating as the surge happens. Perhaps it is hanging and overshooting .

To do the sort of troubleshooting and diagnostics you're doing, may I suggest you invest in the Rinda Diacom software. A few of us here have it, and we all say the same thing. Pays for itself the second time you use it. Your surging could be the TPS, or an IAC not working properly, both those problems would show up on the Diacom software.

I just got this boat a few weeks ago. I am still learning the systems but I have a long history with Volvo Penta small block Chevy motors. There are no alarm codes active that have sensors related to this motor. I do have a buddy with a Rinda techmate pro and we scanned it.

As far as the engine mechanicals, Volvo, Merc same same... The difference is in the fuel and ignition systems... The Diacom is so unbelievably useful. I have used the package on EFI outboards, and a Merc Verado too.

Chris.......

 

[Kodiak2359]

Chris
Yes, Alaska. There are of course Mercruiser dealers and mechanics in the state just not in our vicinity. We would be a 14 hour ocean ferry ride from the nearest.
When we put the scanner on the engine there was definitely a difference, the scanner reading something like 18 degrees lower. I will be plugging it in again to determine the difference.
I agree the software would be best. While I would love having the software the price of the scanner or the software seem OBSCENE. That's what happens when you have proprietary protocols. Too bad there is such a wealth of information available but Mercruiser decided to hold it hostage for dealer profit. If I remember right the software is 8 or $900 . If they have a half off sale I'll probably jump on it.
Thank you for the reply and your help.

 

[achris]

Chris
Yes, Alaska. There are of course Mercruiser dealers and mechanics in the state just not in our vicinity. We would be a 14 hour ocean ferry ride from the nearest.

Ouch!

When we put the scanner on the engine there was definitely a difference, the scanner reading something like 18 degrees lower. I will be plugging it in again to determine the difference.
I agree the software would be best. While I would love having the software the price of the scanner or the software seem OBSCENE. That's what happens when you have proprietary protocols.

Indeed. I have an GPS chart plotter that is Canbus and an input page for engine data. Decided to connect the engine canbus to the plotter. Found a local shop selling the Delphi connectors (Merc wanted over $100, go them for $11), and connected it all up...No talkies... ??? Merc's canbus is NMEA2000 in hardware, but the software protocols are different. Merc want over $400 for the converter... Yeah, NO!

Too bad there is such a wealth of information available but Mercruiser decided to hold it hostage for dealer profit. If I remember right the software is 8 or $900 . If they have a half off sale I'll probably jump on it.
Thank you for the reply and your help.

I was fortunate that I bought the software when the Aussie dollar was about $1.10 US, so it wasn't so bad. Now, at $0.71, I'd be looking at $1,000. Diacom is $699 USD on the website

Chris........

 

[Scott Danforth]

the dash gauge is a $2 sender with a $3 gauge with the internals of the gauge made in India. they are not accurate as Chris stated. however a bit of corrosion on the connections will add temp.

the software is still cheaper than a dealer visit.

 

[Kodiak2359]

It's very possible the temp sender lead is loose or corroded. I've found a few corroded and loose connections on this engine. If I had paid to put a 2018 long block in it, I would have everything spotless and tight. The guy who installed this would never do work for me. I'm going to pull the IAC and see if I can install it on my buddy's engine which is three serial numbers different than mine and see if the surge moves to his boat.

 

[Kodiak2359]

The IAC operated fine on the other engine. I pulled the TPS and the the MAPT sensor. Both looked fine and were reinstalled. More testing tomorrow.

 

[achris]

Kodiak2359 did you get my PMs?

 

[Kodiak2359]

Saturday I figured out that the heat exchanger cap was not design to allow coolant flow back in the tank. It let's it expand to the overflow bottle but not come back. Big sucking sound every time I opened the cooled exchanger tank. Put a new one on for $8. The gauge is still reading high (195 ish) but the Techmate pro and the infrared say 156 f.