Not enough RPM at 6.2 mpi / sea ray 270

[Andreas G]

My 6.2 mpi horizon Bravo III cannot get enough RPM's.
I was out for 20 days using the boat every day and I could accelerate easy at 5200.
I came back I let the boat one week at the marina and the problem starts..
If its under load and underway (water & fuel full) goes at 3200.
It starts ok and goes perfect until 3200 after that nothing!
I press more the throttle and ?? nothing, if I press the throttle at WOT very slow it will go at 3400 (at 2900 ? 3000 comes of the hole)
If the tank is ? and no water / waste, the boat accelerate perfect until 4000? and stops there again.
If I accelerate with out gear in the engine work perfect and reach 5500.
Engine hours 220, bottom and props clean, fuel filters clean, tank air vent clean, temperature little higher than 170 (analogue temp meter), oil pressure as usual, flame arrestor clean, throttle cable ok.
This summer gimbal bearing and yoke replaced
The mechanic check it, (not test drive) he used marine diacom software. The engine is new he told me.
Anyone had this problem?

 

[Don S]

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

Gonna need year, Serial numbers, etc.

 

[JustJason]

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

did your boat get rained on and your pumps arent working?

Because that's about the only thing your going to be able to check yourself.... with maybe the exception of their being a boat side fuel supply issue.

Get Don your serial #. And if you like do a search for "engine does not reach WOT"

When was the last time you changed your fuel/water seperator filters?

 

[Andreas G]

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

model number MCM MX 6.2 MPI
SERIAL OM653115
No water the pumps are ok.

 

[Andreas G]

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

The service was at August.
all the filters are new.( gas and oil )

 

[JustJason]

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

The filters aren't that old... but stranger things have happened.


When was the last time it had a tune up?
Cap/rotor/wires and plugs?
Are they all original?

Its gas, spark, and compression.... your missing 1 of them.

You can try pulling all your plugs and looking at them... see if they all have realatively even wear, and none of them are rusty. While they are all out give it a compression test, especially if you've never done one on this engine. It's nice to have numbers on a fresher engine so as time goes on you can compare them should you need to do a compression test later.

 

[Andreas G]

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

I bought the boat this summer (190 engine hours) and I made it a service
Gear lube, gimbal bearing and yoke replaced
All the filters oil and the mechanic check it with diacom marine software.
After the service I went for 20 days - vacations and I had no problem,
The problem starts when I came back. I left the boat at the marina for one week with out start the engine, after that the throttle goes "empty" after the 3400.
I change two mechanics but no one can do something.

 

[JustJason]

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

well.... diacom is good but it doesn't solve everything.

Make sure your mechanicals are okay before you go on to your fuel and ignition systems. Or else your going to be like a puppy, chasing your tail in circles.

 

[Andreas G]

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

Tomorrow morning a merc tech will come to check it with mercruiser software.
Tomorrow I will record the data ..

 

[newport dave]

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

Check the Shift Switch. If the ECM thinks it's in neutral, it won't let the engine rev beyond 3500RPM.

 

[Andreas G]

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

ok thank you

 

[JustJason]

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

If I accelerate with out gear in the engine work perfect and reach 5500.

Check the Shift Switch. If the ECM thinks it's in neutral, it won't let the engine rev beyond 3500RPM.

Hmmmm.... wonder why it rev's to 5500 no load in neutral..... Dave may be on to something.....

BTW... its bad for your engine to rev it that high in neutral Andreas.

 

[Gary H NC]

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

A motor running on half the cylinders will rev to 5500......thats a pointless test..

 

[JustJason]

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

A motor running on half the cylinders will rev to 5500......thats a pointless test..

unless the ecm is supposed to limit it....
Because then you can say....

Why isn't the ecm doing it's job.... is it an input problem or an output problem.

 

[Andreas G]

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

it is not the cylinders we perform an injector test and I listen all the cylinders one by one. Also the engine sound is normal no shake or other crazy staff.
If you don?t accelerate more than 3500 you cant understand that the engine have a problem and if you test it at natural ( no gear) every thing is perfect.

I was at the boat before and I check the switch. The switch looks ok not broken but I don?t know if it giving a false signal to ECM
I also notice that the part no13 (see Attached pic) is moving 2-3mm in out. This is possible to disturb the button of the switch. The screw no14(see Attached pic) is not tight enough.
The question is: the mechanic how come tomorrow will notice that through the diagnostic? and if the switch is giving false signal he can reset it or reprogram it?

thank you very match all for your help.
tomorrow i will have more information.

 

[Don S]

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

The picture you have is a shift interrupt switch, not the neutral safety switch Dave was referring to.
Besides, your Bravo III doesn't even have a shift interrupt system. So, why do you have a Bravo III outdrive and an Alpha shift interrupt system on the engine ??????????

 

[Andreas G]

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

The power pack has been replaced by the previous owner.
Shift, throttle and instruments are from the older pack (7.4).
The mechanic today told me that the IAC doesn?t operate normal.
What I saw : he open the IAC menu there was a rolling bar ( the engine was off) he moved the bar + and I could listen the sound of the IAC when he put it to ? nothing.
And when the throttle was at WOT the software had 80,9% of power.
He told me that throttle cable and IAC valve must be replayed.

 

[TilliamWe]

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

Ok, so the throttle cable is out of adjustment and not allowing the engine to reach full throttle. Makes some sense. I wonder about the IAC, because that stands for Idle Air Control. What does the idle of your engine have to do with it's ability to run at WOT? Maybe it does, I am not Mercruiser mechanic, but I'd hate to see you throw an unecessary part ($$$) at this engine. Best of Luck.

 

[Andreas G]

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

I believe your right about the IAC.
Throttle cable is the first to do.
Thank you

 

[newport dave]

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

The mechanic today told me that the IAC doesn?t operate normal.
What I saw : he open the IAC menu there was a rolling bar ( the engine was off) he moved the bar + and I could listen the sound of the IAC when he put it to ? nothing.

I've been using Diacom for years and I have never been able to get the IAC test to work correctly. I wouldn't replace the IAC based on that test. There are three things you need to look at to determine if the IAC is functioning properly;

1)Normal IAC behavior - 99.98% Duty Cycle for the first two to six minutes, then dropping to around 30% as the engine reaches operating temp.

2)The engine is able to maintain the correct (desired) idle speed - 550RPM at full operating temp for this engine.

3) IAC output fault - If you settting an IAC fault, replace it.

Also, as TilliamWe suggested, a bad IAC will not cause any loss of RPM at WOT. However if you have an active IAC fault, the Engine Gaurdian will reduce the Available Power to 90%, lowering the rev limit to 4600 RPM.

And when the throttle was at WOT the software had 80,9% of power.

Thats a little confusing, did he have 80.9% Throttle Position, or 80.9% Available Power?