Engine issue— Mercruiser 5.0L, 305, 2 barrel mercarb

[nennedk]

Twice today, with about 4 hours in between, I was cruising at 6 knots when the engine suddenly lost power. It started running really rough and then died completely, with a small puff from the carburetor. Luckily, it restarted without much hassle and I was able to continue sailing each time. This is the first time it’s ever happened.
Has anyone experienced something similar or know what might be causing it?

 

[Bondo]

Ayuh,...... Check the fuel filter for water,.....

 

[nennedk]

Its look clean to me. No separation. Other thoughts?

 

[bajaman123]

How many hours on the engine? How long since (if ever) the carburetor has been serviced?

 

[nennedk]

How many hours on the engine? How long since (if ever) the carburetor has been serviced?

Around 520 hours. 320 hours since last carb service, in 2017.
Distributor, distributor sensor and spark wires changed this spring.

 

[kenny nunez]

Try running the boat with the engine cover open the same exact way to see if it continues running. Or with the bilge blower on. It could be that the heat from the non jacked exhaust manifolds are building enough heat in the enhine cover to cause vapor lock or boiling the gas in the carburetor.

 

[nennedk]

I went out the day after, and it all seemed normal again, no dying engine. It was though a very hot day when it happened, so maybe that could be the cause. It's hard to reproduce because I was moving with 6 knot about at least an hour both times before it happened and the temperature has gone down again.