Mercruiser 3.0lx cut out at full throttle

[Jonny2018]

Hi All,
I have a 96 mercruiser 3.0lx, I've done the distributor, ht leads, ignition coil, and had the carb rebuilt.
She runs fine and gets on the plain nice and easy.
However.....
Today racing the tide she cut out at full throttle. No sputtering bogging down etc just went. I fired up the aux and started googling back in after about 5 mins she fired back up and ran well at full throttle all the way home. This is the first and only time this has happened.
She fires up first time, but when I'm sitting on the water she can be hard to start and if running idle she cuts out after 5-10 mins although this is infrequent. If I try pumping before firing she doesn't like that but will fire with the throttle in the 'home' position easily.
I'm not sure why but I've never trusted the clutch. I know the clutch is activated by it's own independent from how hot the engine is etc, could this be the cause or something else.
Ta!

 

[jimmy_the_builder]

I had a Merc 4.3 in my first boat and it had an oil pressure switch low down in the engine block; the wiring to this became unreliable with age and caused the engine to just stop in the way that you've described. I don't know if your engine has this oil pressure switch - but if it does, I'd start there.

 

[BruceK]

I've had that engine previously. Same symptoms. Might be idiosyncratic of that engine. A carb rebuild to spec, not just slap the rebuild kit in, made a huge difference.
To add to Jimmy, did you repalce the condensor when you were doing the disti and HT leads. Mine was prone to slow failure. I always carried spares.

 

[TheOrs]

I've never trusted the clutch.

Do you mean 'Choke'?

I agree with Jimmy - An electrical problem of some kind. Wiring or a sensor getting hot.

 

[Jonny2018]

Haha yes clutch. I'll start with the oil pressure switch then....in the hope, unlike most things on this engine is a simple job.

 

[Jonny2018]

No condenser was not changed. I've had a look about although they are pennies I cant seem to find just the condenser in the uk. Know of anywhere I can purchase from?

 

[Boat2016]

Have you got the micro switch on the gear selector ? if faulty or not set up correctly that can cut engine at an inconvenient time.

 

[QBhoy]

I’m with the shift interruption switch being triggered or fuel pick up being blocked in tank. Or it’s a loose connection somewhere. The oil pressure switch is unlikely to cut your engine out on a basic engine of this age.

 

[Hoblands]

I had this some years ago on a 5ltr fitted to a Rinker 242. After much searching I found it to be a loose / corroded wire on the back of the the ignition. Worth a look?