Engine Mystery!

[Steve L.]

Hello all,

Looking for a motor detective here. I have twin 350 Mercruisers from the year 2000. They are the MPI motors.

The starboard motor has the following symptoms:

-half the time I go to start it, it needs throttle to start - then rev it a few times and it is good to go all day, even if I stop and start it occasionally.
-even if it does start the first time, it sputters to get up to idle
-it runs about 148 degrees, while the other motor does about 160
-oil pressure is slightly lower than the other motor.

Here is what I have done so far:
-June 2020 - full tune up, including plugs, oil, etc.
-July 2020 - all new fuel injectors, thinking that was the problem

No change.

Any ideas?

THANKS!!

 

[hottoddie]

Need some more info. Are the engines fresh water or raw water cooled? How many hours? Has a compression or leak down test been performed?

 

[Espos4]

Hello all,

Looking for a motor detective here. I have twin 350 Mercruisers from the year 2000. They are the MPI motors.

The starboard motor has the following symptoms:

-half the time I go to start it, it needs throttle to start - then rev it a few times and it is good to go all day, even if I stop and start it occasionally.
-even if it does start the first time, it sputters to get up to idle
-it runs about 148 degrees, while the other motor does about 160
-oil pressure is slightly lower than the other motor.

Here is what I have done so far:
-June 2020 - full tune up, including plugs, oil, etc.
-July 2020 - all new fuel injectors, thinking that was the problem

No change.

Any ideas?

THANKS!!

Has the IAC ever been replaced? (Idle Air Control)

 

[bobeast]

When you first turn on the ignition, prior to starting, you should hear the fuel pump pressurizing the injector rail. When you hear it stop pumping, check the fuel pressure. Then compare it to the other side.