99 MerCruiser 454 L29 in Carver 406 - Failed to stay running then OK

[bud37]

So here is another tidbit......if your aft tank was not used for years before you and you are now buying fuel that has ethanol this could be an issue as ethanol will clean everything in that system....at least that is my understanding of the chemistry.

[kgarguilo]

Source of the post Next time you go out set the fuel feed for each engine to a different tank, if I understand you saying that both engines are pulling from the same tank.....separate them would be my advice at this point and we will see.

We will go out tomorrow. Thanks! CORRECT - Both engines are pulling form the Aft tank.

[kgarguilo]

Source of the post So here is another tidbit......if your aft tank was not used for years before you and you are now buying fuel that has ethanol this could be an issue as ethanol will clean everything in that system....at least that is my understanding of the chemistry.

Only Non ethenyl (real fuel) fuel is being used.

[km1125]

Source of the post

Have you checked/changed the anti-siphon valves??

I do not know what that is or where I would look for it. Is that the overflow for each tank?

The anti-siphon valves are on each fuel tank source. If you switch to a different fuel tank then you'll switch to using different anti-siphon valves. That might be the easiest test. Perhaps just put the port engine to port tank and the stbd engine to stbd tank for a test.

They are located right where the fuel line connects to the fuel draw tube on the tank. It is a small valve, and usually looks like a long hose barb adapter. It screws into the tank fitting, then you put the hose on it.

The other issue that I've hear about, but never personally ran into, is where hotter engine water will 'migrate' into the cool fuel module while you're sitting after running for a while. This heats the fuel in the module and can create conditions conducive to vapor-lock. I do not know if this affects the Cool Fuel II modules or just the original Cool Fuel modules. Perhaps Viper or someone else more familiar can weigh in on that one. One of the solutions to that issue is putting a one-way check valve in the cooling lines going to the Cool Fuel module.

[kgarguilo]

Source of the post If you went right to the anchorage and shutdown, but then tried restarting the motors within the first 15 min or so you would NOT have the problem, but if the motors are sitting for HOURS in extended heat that is when they don't restart. Is that very consistent or are there times when it would not restart after just sitting for a short period of time?

Source of the post Next time you go out set the fuel feed for each engine to a different tank, if I understand you saying that both engines are pulling from the same tank.....separate them would be my advice at this point and we will see.

BRIEF UPDATE:
Before starting the engines, I switched tanks for both engines.
Port Engine now on Port tank (was on aft)
Starboard Engine now on Starboard tank (was on aft)
Generator also pulling off of Port Tank

We headed out to our regular cove, once arriving I dropped and set the anchor and waited for the boat to settle into the wind to make sure we were in a good place. I then turned the engines off and set a 15-minute timer. The Generator continued to run as usual. Once 15 minutes passed, I started the Starboard engine first and let it settle into idle, Next, I held my breath and started the port engine, it started and after both engines were running for a few minutes I started to bring up the anchor drawing about 35 amps, but voltage was holding over 13.2V. We puttered out of the cove and began our journey back to the dock with no issues.

This is encouraging. I will try this coming week to go out for 5 or 6 hours on the hook again and see if this behavior repeats. Wish I had more time to do this today but sadly I do not.

Deduction from today: If this behavior holds the real tank vent valve and anti-siphon valves are suspect.

Thank you all for your continued support!

[bud37]

Kevin, nothing pops out from the recordings for me except what appeared to be the surging as the throttle was not moving.....maybe just the fuel issue.......try to slow the amount of packets down and watch them that way....it is time consuming but just maybe you can pick up something happening, if there actually is something to see there in the future.

Do your boat engines have the shift/load assist....where the engines adjust rpm as you put the boat in gear either forward or reverse with the throttle set at idle, then settle back ?

[kgarguilo]

"bud37"]Source of the post Kevin, nothing pops out from the recordings for me except what appeared to be the surging as the throttle was not moving.....maybe just the fuel issue.......try to slow the amount of packets down and watch them that way....it is time consuming but just maybe you can pick up something happening, if there actually is something to see there in the future.

The only thing I can think of is I was raising the throttle and back off to get it going. That may have contributed to teh surging you are seeing.

Do your boat engines have the shift/load assist....where the engines adjust rpm as you put the boat in gear either forward or reverse with the throttle set at idle, then settle back ?

Not that I am aware of, But, when I typically put the boat into gear at 600 RPM it typically stays at 600 RPM adn when shifting out it stays at 600 RPM.

[kgarguilo]

Source of the post This is encouraging. I will try this coming week to go out for 5 or 6 hours on the hook again and see if this behavior repeats. Wish I had more time to do this today but sadly I do not.

Just an update / non-update - I was not able to make it out this week due to storms in my area. I will attempt to stay out on the hook this coming week for the 5/6 hours again. Worst case Saturday, we have plans to raft up with others.

[bud37]

Source of the post Worst case Saturday, we have plans to raft up with others.

Then it won't matter if you stay longer then...... .....

[kgarguilo]

Source of the post Postby bud37 » July 28th, 2023, 5:13 pm

Next time you go out set the fuel feed for each engine to a different tank, if I understand you saying that both engines are pulling from the same tank.....separate them would be my advice at this point and we will see

Ok, first SUCCESS!!!

As suggested by Bud37 and echoed by others we switched tanks for the engines, If you recall, the engines were both running off the aft tank alone. I swapped the port for port and starboard for starboard tanks. The 15-minute (Anchor for 15 minutes then start and leave) test performed last week recommended by km1125 performed admirably.

Today we were able to leave the dock at 10:15 AM and traveled to a similar distance cove. We spent 3+ hours in the cove on the hook. We started one engine at a time and let them come up to temperature, raised out anchor and off we went back to the dock.

Funny side story, we have a friend with a Carver 396 with 8.1 engines that visited us at our dock last Saturday night and we were talking about this problem and before I could tell him where I was at... He had the same issue Anti-Siphon valves years ago. He ended up cleaning his with a carburetor cleaner fluid and all has been working for years. He did this because he could not find an exact replacement.

A Hearty thank you to all of you who invested time on my issue. I will post one more time to this thread after the Anti Siphon valves are replaced with a condensed version of the whole thread for the next person that has this issue. You all are the best! Happy Boating!!