stalling at deceleration

[oddysea1]

I have a [2000]-0l301745- 350 Merc cruiser magnum-mechanic replaced following with all Merc cruiser parts-cap and rotor kit-spark plugs-fuel pump regulator-fuel injectors-wires- throttle position sensor-fuel filters.Still runs rich and rough but less so since tune up it will stall at a fairly quick deceleration during a docking type situation not dropping from 3500 rpms to 800. Any possible parts that should be looked at ? I do not have a scanner but would be interested in how thorough it is in diagnosing issues . I am a little tempted but it is pricey . All help is appreciated -this is a great resource-always recommended to fellow boaters

 

[alldodge]

The Merc mechanic threw a lot of parts at the problem, wonder if they did any kind of testing prior.

situation not dropping from 3500 rpms to 800

Are you saying that when the throttle goes to idle or neutral its idling at 3500?

 

[Rick Stephens]

Or does it stall when you pull into neutral?

 

[oddysea1]

The engine was in need of a lot -he did use the tech mate scanner-it helped some of the issues but still not there-stalling in gear during deceleration-holds about 800 rpm in neutral-650 in gear both motors same rpm-the port engine uses more gas and has this issue of stalling ,running rough , not as responsive during acceleration .Smells rich with some black smoke.

 

[alldodge]

stalling in gear during deceleration-holds about 800 rpm in neutral-650 in gear both motors same rpm

Sorry but this is not real clear, have trouble with new English

Are you saying, both motors idle at 800 in neutral and 650 in gear?
There isn't any deceleration issue other then when the port motor goes in gear it will die, correct?

engine uses more gas and has this issue of stalling ,running rough , not as responsive during acceleration .Smells rich with some black smoke.

The port motor runs richer and does stall/die, and when accelerating it does do as well as the starboard

If above assumptions are correct, then I would check fuel pressure because pressure may be to high (43 psi) or injectors are leaking.

 

[oddysea1]

I was stating that both engines idle in neutral and in gear at the same rpm.The troubled engine that has the indicated issues including the stalling problem occurs when- you decelerate from 1500 rpm to a dead stop on the throttle in a fairly quick move that is when it stalls.The other engine runs fine-no issues-Question -if the injectors were leaking would I have gas on the block or any other physical indication?I will look into fuel pressure-Thank you

 

[oddysea1]

Sorry on previous post I meant to say deceleration from 1500 rpm to 800-need better glasses

 

[alldodge]

If injectors are leaking the motor would run rough because one or more would be leaking. If pressure is to high then all will be supplying to much fuel.

The stalling could be the IAC needs cleaning or replacing, or if pressure is to high hen its just flooding and the IAC is unable to compensate

 

[oddysea1]

new to inboards -will get manual-what does the IAC


stand for? looking to do some of this myself= getting expensive-The fuel pump regulator replacement did help maybe IAC is something to further the improvement-Thank you Andy

 

[alldodge]

Idle Air Control, which is a air valve on the throttle body and is controlled by the ECM.
Its listed as "NS" which means not shown and part is below item 13 on the list

https://www.mercruiserparts.com/bam/subassembly/31608/2716/110

 

[oddysea1]

Very hot today will check out IAC tomorrow got some info on location and will move forward on possible replacement and or cleaning /will keep you posted thank you for sharing knowledge