3.0 GS does not fire on 1 cylinder when idling back into the box after a ride

hey gents !

the boat starts great and runs great, but after the boating the engine starts to become rough and cuts out on one cylinder when i idle back into my box at the marina. this happens only after the boating- never at startup and idling out of the marina.

i issued it to carb problems and just rebuilded the carb fully with VP OEM parts - result the same, the rebuild was for nothing and i learned the lesson ...

i currently run out of ideas- do you have any ?

thanks much !

Re: 3.0 GS does not fire on 1 cylinder when idling back into the box after a ride

The miss is caused by lack of fuel or lack of spark. Which one is gone when this happens? Spark is easy to check for. If there is spark, then fuel is the issue. It is certainly possible that a valve problem is causing the miss -- such as a bad hydraulic lifter.

Re: 3.0 GS does not fire on 1 cylinder when idling back into the box after a ride

I detonated my #1 spark plug on the first boat I owned with that trusty 3.0l engine. It still ran! Heck, it barely missed a beat except at idle it was rough.

Check your spark plug in that cylinder. Replace it if its questionable. On mine, the electrode was completely gone and it was obvious to see what the problem was.

You could also have a cracked insulator on that spark plug, an arcing plug wire, etc.

Re: 3.0 GS does not fire on 1 cylinder when idling back into the box after a ride

thanks gents !

it cannot really be the fuel i think. like said - carb has a full rebuild with 30 minutes of operation on it. the boat has normal power and no issues when opening the thrlottle. of course i also changed plugs - they are brand new. just before the rebuild they look a little rich , and i found the float setting a little on the rich side which now i corrected, idle mixture is also correct. i have good spark on all 4 cylinders ( checked this )

Silvertip said:

It is certainly possible that a valve problem is causing the miss -- such as a bad hydraulic lifter.

Click to expand...

i thought in this direction also. the engine has indeed a slight tickering noise like one pushrod is slightly loose. i may go and adjust the rockers but it should be not really needed due to hydrlaulic lifters.

would a collapsed lifter not affect top end power ???

i even thought about a leaking exhaust riser ( the manifold is half a year old, can be excluded ) that lets water via the exhaust to one cylinder and cuts it at idle but thats all a very rough guess.

problem is that now i stand on the edge in throwing serious money on it without being sure what is bad - e.g change the riser although it might be good, next would be the fuel pump , change lifters etc etc...