Not enough RPM at 6.2 mpi / sea ray 270

[Andreas G]

Re: Not enough RPM at 6.2 mpi / sea ray 270

the last mechanic used mercruser diagnostic soft.
he press the Throttle at wot and it was 80,9%. this is position?

Anyway, I test it at wot by pressing the plastic where the cable throttle ends and nothing happened. The engine went at 3000 easy but, 3400 after 2min and 3600 only when I turn the boat to heave the wind at the back.
As for the IAC the engine doesn?t have any active fault at all, the mechanic said that it doesn?t work correct.
I am totally disappointed.
Tuna fishes and I cant do anything about it??????.!!!!!!!
Every body say that the IAC can?t fix the RPM problem even if I replace it.
If the filter which is under the IAC is dirty can do me the RPM problem?
Can it be an ignition coil problem that the mechanic and the mercruiser diagnostic sys cannot understand it?

 

[JustJason]

Re: Not enough RPM at 6.2 mpi / sea ray 270

IAC stands for "Idle Air Controll"
Its a valve.
Basically, at idle, your main throttle plate is completely closed, alowing very very little air past it. The IAC is an electronicly controlled valve, set up on a bypass air circuit. It is the IAC valve that meters the amount of air the engine as available, but only at idle. When you get off idle, up to your midrange, and towards WOT, the IAC closes (or it is supposed to close), and all of the air is then metered through the main throttle plate.
Now if you had an iac that was sticking open, you could be getting a lean condition. And possibly some knocking.

As Dave asks, is the 80% total engine power available??? (guardian mode, and you should have an active fault in memory) Or is the TPS (throttle position sensor) reading 80% when it should be closer to 100% at WOT.

Does diacom show a spark knock at all?

Like I said before, diacom is good but won't show you everything. You still may want to do a comression test, or as a shortcut, find somebody with a KV Meter and measure your spark discharge voltage, an erronous reading on 1 cylinder or more will indicate a problem.
Whats your fuel pressure look like??? If your a couple of PSI down your not going to get WOT out of the motor.

 

[Andreas G]

Re: Not enough RPM at 6.2 mpi / sea ray 270

The 80,9% is TPS reading.
He tryed to adjust the cable but he couldnt so he said that i must replace it.
So i took the boat out of the marina and The engine went at 3000 easy but, 3400 after 2min and 3600 only when I turned the boat to have the wind at back.
The mechanic was official mercruiser so he had the official mercruiser software and not the diacom one.
I ask him to check the knock sensor and he told me that the sensor is ok and there is no spark knock at all.
fuel psi was up to 48 according the Rpm so he said that there is no problem at the high pressure pump.
At the end he said engine is perfect you must replace the throtlle cable and the IAC valve.....
Now i am waiting from the mechanic to mail me the recorded data of the tests he ran on the engine.

thank you Very much guys for your patience you are my only hope...

 

[Andreas G]

Re: Not enough RPM at 6.2 mpi / sea ray 270

Recorded Data 1 Value Units
Engine Speed 562 RPM
Battery 13,8 Volts
Power 1 5,03 Volts
Baro Pressure 29,96 in. Hg
Manifold Pressure 16,14 in. Hg
Available Power 100 %
Guardian due to None
Throttle Position 0,12 %
TPS 1 0,62 Volts
Load 12 %
Spark Advance 9 BTDC
Knock 1 21,494 KHZ
Idle Air Temp 100 % DutyCycle
Block / Sea Pump Pressure 0,83 PSI
Engine Cooland Temp 71 C
Manifold Air Temp 32 C
Oil Pressure 42,5 PSI

Recorded Data 2 Value Units
Engine Speed 1468 RPM
Battery 14,51 Volts
Power 1 5,03 Volts
Baro Pressure 29,96 in. Hg
Manifold Pressure 10,96 in. Hg
Available Power 100 %
Guardian due to None
Throttle Position 7,08 %
TPS 1 0,889 Volts
Load 5 %
Spark Advance 10 BTDC
Knock 1 16,263 KHZ
Idle Air Temp 73 % DutyCycle
Block / Sea Pump Pressure 5,86 PSI
Engine Cooland Temp 58 C
Manifold Air Temp 24 C
Oil Pressure 50,8 PSI

 

[JustJason]

Re: Not enough RPM at 6.2 mpi / sea ray 270

ok......

disconnect the throttle cable.
turn the key to the run postion, but do not start the boat (KOEO)
manually open the throttle plate all of the way.
What does your tps read in both percentage and voltage?
it should be real close to 100% and 5VDC.
If its not check your connector for corrosion, and i don't have it in front of me, but there will be resistance check on the tps itself too.


EDIT: I just got your pm Andreas. let's keep things in the thread so everybody can read an learn.

After thinking about it again for a second. Data stream 2 doesn't really mean anything, your not having a problem at the 1500 rpm that it was recorded at, you have a WOT problem.

Out of your 3 mechanics. has any of them done a cylinder drop test? a fuel supply test? a compression test? Are they suuuuuuure they know how to read the diagnostics screen?
I've been to merc school, they pass you if you just show up on time and don't leave early.
it's sad really.

 

[Don S]

Re: Not enough RPM at 6.2 mpi / sea ray 270

At this point, I would stop worrying about the IAC, TPS, and look for problems that will cause a problem with the WOT. the IAC is only used at idle, and will not have anything to do with WOT.

I would start by doing a fuel system test, including replacing the fuel filter water sperator and inspecting the old ones contents for water.
Then do this test.
http://forums.iboats.com/showthread.php?t=167561
If you are sucking air, you won't get WOT rpm.

Have you checked the fuel pump pressures? Does your engine have a boost pump?

If all that checkes out ok, then do an injector balance test. I had a Volvo 8.1 have a similar problem that was caused by bad injectors. Replaced 3 and it ran fine again.

 

[JustJason]

Re: Not enough RPM at 6.2 mpi / sea ray 270

your up early Don.... what is it... 6 am out there?

Edit: yawn.... are ya sure the tps won't cause a wot problem?

 

[Don S]

Re: Not enough RPM at 6.2 mpi / sea ray 270

I've been up since 5, which is when I normally get up, had 3 cups of coffee and ready to go.

The TPS could be a problem, and can be easily checked, but I doubt it's the problem. The TPS voltages look fine in his examples, but the idle rpm is low, which could also be a problem with the fuel system or the IAC, his problem is at WOT.

 

[Andreas G]

Re: Not enough RPM at 6.2 mpi / sea ray 270

captJason I am not sure that they understand the numbers, actually I belleve tha they don?t.
Don S
I already replaced the fuel filter and the water separator. No water at the old filters.
I have a boost pump and a high pressure fuel pump and the pressure at the fuel system was 43 psi (at the last test). I also made another test: after I replaced the filters I put a new fuel hose from the tank to the boost pump to check if the older hose had some hole. I also check the tank air vent.
Is it possible this tank to have a valve where the hose is connected with the tank??( I didn?t check that but sea rays manual doesn?t say something like that)
The last mechanic ran an injector test and the previous one he disconnected instantly one by one all the injectors to listen the engine while was running at idle. My mind goes to ignition coil and to the distributor is it possible?
I become a member of the seloconline site to learn more about the engine but it doesn?t say how can I check the ignition coil.

Engine accelerate perfect until 3000 and after reacts like in guardian mode but is not


Some pics from the engine

 

[JustJason]

Re: Not enough RPM at 6.2 mpi / sea ray 270

ugh... 5 is to early for me... i'm more of a 630-7 guy.

Andreas.... like i mentioned in my first post, this is going to be a tough one to check yourself. You can try and stab at it, but it's going to get expensive quicky swapping parts.

http://www-alt.mercurymarine.com/mne...24/24covr1.pdf

That should be the service manual for your engine (courtesy of Don).

It very well could be the coil, but then again, it very well could not be.

I'd start with the fuel supply first. There's a post someplace here about it and it's not that hard to do. Maybe Don will chime in with the link.

Then maybe to a cylinder drop test.
To do that you need a pair of insulating spark plug wire pliers. They are usually all plastic. With the engine at idle, pull 1 spark plug wire off the cap. Listen or look at a shop tach for a small drop in idle rpm. You should have one. Do all 8 1 at a time. if you come across one that you do not get a drop in rpms. then you have a problem on that cylinder. It could be ignition or compression related, but it will point you in the right direction.

 

[Don S]

Re: Not enough RPM at 6.2 mpi / sea ray 270

That's the manual used to cover the engine, but not your ECM, you need manual #36 for the 555 ECM.
Here is the link to that.
http://www-alt.mercurymarine.com/mnetdata/SERVICE/CRUISER/Servmanl/36/cover36.pdf

Also, an injector balance test is NOT pulling the wires off each one and seeing if the engine changes. Even if the injectors fail the balance test, you would still hear the engine change sounds if you disconnect them.
Manual 36 explains the proper way to do the test.

My mind goes to ignition coil and to the distributor is it possible?

Then change the coil. And go for a ride. Then come back and we will dig into your problem some more when you are done throwing money at it and hopeing for the best.

 

[rlatt]

Re: Not enough RPM at 6.2 mpi / sea ray 270

I don't know if you solved your rpm issue or not, but I have a 270 searay with twin 4.3'3. One day a couple of years ago I could not get over 3200 rpm on the starboard engine. I replaced everything you did with no luck. Finally I disconnected the fitting which screws into the gas tank and there was a hunk of metal from the manufacturing process stuck in the fitting which I removed with a dental pick. Engine rpm's picked up immediately but I am still a couple of hundred rpm's less than the port engine and I figure it is a gas line issue.

 

[JustJason]

Re: Not enough RPM at 6.2 mpi / sea ray 270

just a quick comment.
An injector balance test and a cylinder drop test are not the same thing. They are testing for 2 different things.
In a common sterdrive.... an engine that acts funny on a cylinder drop test usually points to a mechanical problem or an ignition problem. It' really never points to a fuel problem.
injector balance, or injector fuel pressure drop.... are 2 different things.
But to me.... if your loosing that many rpms i wouldn't be looking at injectors first.

 

[Andreas G]

Re: Not enough RPM at 6.2 mpi / sea ray 270

First of all I need to THANK YOU all guys for spending your time and your tech skills.
What I am going to do is check once more the fuel line (fuel system check) all from the tank to the high pressure pump as Don S says and I will check also the tank for something like rlatt says.
Then I will make a cylinder drop test as captJason describes.
Then I?ll make a visual check at the ignition coil.
Then I will test it out of the marina.
And I?ll come back with news? good I hope.
If not, pray for me!!!!!

 

[JustJason]

Re: Not enough RPM at 6.2 mpi / sea ray 270

if your going to check the coil you need to check it with a DMM.

 

[Andreas G]

Re: Not enough RPM at 6.2 mpi / sea ray 270

ok.
i have one.
do you have a pdf to show me how to check it with the DMM?
it is this one :
http://www.mercruiserparts.com/Show...=50&bdesc=Distributor+and+Ignition+Components

thanks

 

[Andreas G]

Re: Not enough RPM at 6.2 mpi / sea ray 270

After almost one month the mechanic understands that is something with the exhaust valve from cylinder 3 the valve stay closed.
Why? We must open the rocker cover to see. ?.

 

[Don S]

Re: Not enough RPM at 6.2 mpi / sea ray 270

The first thing any good mechanic should do is check the basics first. Fuel, spark, compression, and for loose connections on anything, especially on an EFI engine with a WOT problem.
For a valve to stay closed all the time may be because of a broken rocker arm, stud pulled out of the head, bent push rod, bad cam, or lifter, hard to say without looking.

 

[JustJason]

Re: Not enough RPM at 6.2 mpi / sea ray 270

On sept 22nd I recomended that you do a compression test.....
Yawn... oh well.
Good luck.

 

[tuna79]

Re: Not enough RPM at 6.2 mpi / sea ray 270

Hey gang, I'm new to the forum and am a mercury/mercruiser tech. Check to see if your plugs are fouled. If the IAC ingest the iac muffler, a small foam peice in the throttle body to reduce noise, it will clog and actually run really really rich which knocks out the plugs and bugs up your higher rpm. Normally though at idle you'll run ragged and belch black smoke, but it happens fairly often. Good luck.