Engine hesitates/sputters on accelaertion

[Rrichr]

New to me 01' SN w/gt40 big boss efi

ran the boat for over 1.5 hours just getting use to it with no problems at various speeds, starting and stopping the engine many times.

My my wife pulled me Slolam using the Perfect Pass and everything was great. I get in the boat and notice the check engine light is now on. We are idling fine with no issues on any of the gauges so I go to accelerate and it starts to miss so I back it back to a fast idle and it runs fine at that speed.

the owners manual says to check and clean the distributor cap and plugs. The cap, rotor and plugs all look almost new. I made sure all the plug wires were connected correctly and took the boat for a ride. Go all the way around the lake and coming back to the dock the check engine light came back on while idling and the same stuttering started again and would not stop. Will continue to run fine at idle.

[Rrichr]

Nautitime answered my question I think under the thread 'GT40 sputtering'

Just had the same problem and I replaced a lot in order to find the problem. It ended up being a combination of the alternator and fuel filter. The fuel filter was the main culprit as it still sputtered a little after I replaced the alternator. Your motor is a little different than mine as I have the pro boss. Check anti siphon valve and fuel filter .. 2 cheapest parts to replace.

Things I replaced to come to this conclusion....
Alternator
Hi and Low fuel pumps
Both relays
Spark Plugs
Wires
Dist cap
Button

[Rrichr]

It is the computer retarding the spark and if I stay under 2700 rpm it runs fine. Researching check engine light scenarios. Sure wish I could plug my ODBII unit in and have it tell me what to replace...

[Rrichr]

It was the oil pressure sending unit right over the oil filter... It had a loose connection.

[Rrichr]

OK, here is the final on it... not the oil pressure sending unit, that is just to communicate to the analog guage and after tightening works fine. It is the oil pressure switch that needed replacing and the old version is discontinued and is replaced with a new one that is almost $40 after shipping/tax. This communicated with the computer and informs it if the oil pressure goes below 5 psi and will then turn the check engine light on and put the motor into limp mode not allowing it to perform over 2700 RPM.

The new switch is taller and required me to tilt the stem which it is attached too a little forward so not to bump against the block and was difficult to re-attach the tan wire to it as it is in behind the fuel/water seperator and my fat fingers had a challenge. I thankfully never dropped the tiny threaded screw and it was early enough in the day where I had the patience required.

Hope this helps someone else as I had to extract this from a culmination of several threads.

God Bless