2007 Carver Mariner help!

[JPS]

I’m at wits end with my 2007 Carver Mariner equipped with 5.7 MPI Crusader gas engines.

The problem is that after about an hour of moderate load on the engines, during which time they idle well and both appear to be running well, but then out of nowhere both will begin to surge and after a few minutes of this, they will cut out all together.

Then I rest them for an hour and they will start up and give me another hour of seeming to work fine, then surge and cut out.

I’ve replaced all spark plugs, distributors and rotors, it just had a new oil and impeller change and the fuel injectors have been inspected and are clean. Most of the batteries are in good shape, 2-3 years old.

Can low power on the house batteries cause this? It’s my understanding that the house batteries and both engine batteries are charged off the same battery charger. I did let them get down to 60% as indicated by VictronConnect battery monitor. At that level I noticed the Ray Marine’s backlight wouldn’t light up much, but when I powered on the GenSet, it came back bright.

Anyone have any ideas?

[km1125]

Both engines should be providing power/charging to the batteries while underway so it should be easy to determine if that is part of the problem. Do you see the voltage readings while running? Are they over 13 volts? Do you have any trouble cranking them after they die (which would indicate depleted batteries)?

I would suspect a fuel issue. You didn't mention fuel filters at all. Have they been checked/replaced? Did you get ALL of them? Sometimes there's a 'low pressure' and separate 'high pressure' filter on the engine, even past your primary water separating fuel filters.

How about the fuel tank vents? Do you know they're both clear? Have you tried running without the fuel caps in place (but being careful not to get water in there)?

How about the anti-siphon valves? Have they been removed and inspected (or replaced)?

[Viper]

Ya I agree, it's most likely a fueling issue and the items km pointed out are pretty common causes. If you do remove the fuel filters, dump the fuel into a clean container and check the contents, and condition of the fuel. Look for water and debris. If you see a lot of debris, you could have a screen on the end of the tank pick up that's getting clogged and after the engine is shut off, the debris falls away from the screen and allows the engine to run again for a while until they clog again. That screen is the last thing I'd check if the other items in the list mentioned are okay as it's likely the most difficult to access.

A good diagnostic tool is to hook up a portable tank but don't go there yet until you check the other items and post the results.

[bud37]

QR_BBPOST The problem is that after about an hour of moderate load on the engines, during which time they idle well and both appear to be running well, but then out of nowhere both will begin to surge and after a few minutes of this, they will cut out all together.

Welcome to the forum..........That sure has all the appearance of fuel starvation......check all the things mentioned above, also clean all your cable connections and grounds.

Question......Is this boat new to you and does this happen to both engines at the same time with each fed from separate tanks ?????.......

[KyleR]

I had something similar keep happening on our generator. Although it is diesel, the symptoms were very similar. It would run for about an hour then shut down. I'd let it cool off, start it again, run for an hour then it would shut off.

As it turned out for us, it was a cooling water issue. The external hull strainer had been painted over repeatedly and as was restricting most of the cooling flow. So the engine would basically run until it overheated, then shutdown on the overheat signal. It took quite a lot of trial and error to figure that out - but now that it has good flow it runs like a top!

Clogged strainers/heat exchangers/etc. would be something else to look at. If it is happening to both engines simultaneously, I would definitely be suspect of the fuel as others have said (unless there is a common seawater intake suction).

Just something else to consider!

[Delorean6855]

It's interesting that it's happening to both engines at the same time. Each engine should be fed by its own fuel tank. If it's a fuel issue, should happen to one not the other...that said, I believe the 2007s have electronic synchronization so maybe it's possible the issue is with one engine and not the other? Are you using the electronic synchronization. Forgive me as my 2004's are less sophistimicated so not sure how it works, only know of it". If it takes an hour for it to occur, maybe related to something that developed a heat intolerance? Fuel pump shutting down?

[Cooler]

A friend had a similar problem. Turned out he had overfilled the oil level when he changed oil. Drained a quart out, and everything returned to normal. He then sold that boat, and I just happened to run into the new owner. That performance problem happened again. Informed the new owner of the previous owner experience. He said he had just changed the oil before the problem popped up. He drained a half quart out, and bingo! Back to running normal. The only difference here is the egines were either 7.4's or 8.1's. Good luck! er