2004 Mercruiser 4.3L almost stalls after low speed forward or reverse

[f575gtc]

Hello everyone,

I have a 2004 4.3 Mercruiser 2bbl carb with TKS and a Alpha 1 Gen II, this season I have been experiencing issues were the engine will almost stall when shifting out of gear after a low rpm forward or reverse move, the engine never stalls but the tach drops to basically 0 RPM for a brief second then goes back to idle.

I have adjusted the shift linkage and set the idle to 720rpm out of water which drops it down to about 700 in water, after I adjusted the shift linkage the boat seemed to work fine for the start of a trip this past weekend but when I got back to the dock it was acting up and almost dying when going into neutral.

It is hard to explain exactly what is happening, if I go into a decent RPM in forward for example 1500 rpm or higher and back to neutral the issue doesn't happen but if I shift into gear and stay around 800-900 rpm to get moving slowly forward or in reverse then have to shift back to neutral the issue happens, it is most problematic when I need to load the boat up and I need to move slow around the dock and onto the trailer

Does this sound like a sticking or binding shift cable or a carb tuning issue? Didn't have the issue last year at any time and it was a bit odd that it worked fine earlier in the morning and not in the afternoon, maybe higher temps are leading to a lean condition and starving the engine for fuel down near idle and not up top where it might be getting more fuel?

I am also having a really bad dieseling issue so I am wondering if everything has to do with a idle mixture that is too lean, I know a Mercruiser service bulletin calls for enriching the idle mixture to attempt and fix the dieseling so I wonder if that may fix this issue as well.

Thanks in advanced for any help.

 

[Scott Danforth]

could be either.

for dieseling, check the quality of your fuel, check your timing and idle a bit before shutting down. that rattle at the end when it stops dieseling is the motor running backwards and sucking in water from the exhaust

for the stalling, check the shift interupt switch. if you cant adjust it, then replace the lower shift cable.

 

[Rick Stephens]

AD knows whence he speaks. I would only add that an improperly tuned engine can cause dieseling, dying and idle issues. I would feel the need to start at A and travel through Z on a tuneup guide. That means fuel source, carburetor, ignition and timing. And depending on results, may also include getting a compression test to verify engine wear state. I am NOT saying throw tuneup parts randomly at the engine and call it tuned. I see many of what are considered high level professional shops that think that is the method to solving any problem. Inspect, clean, determine quality of components. Don't be afraid to do a carburetor rebuild though. That is a justifiable application of labor and a few dollars.