Boat runs great for under a minute, and dies....( I'm lost )

[leroyd92]

I'm chasing an electrician issue with my boat.

The motor runs great at idle, gets on plane with no hesitation " 26 foot cabincrusier " runs for close to a minute before it starts lightly surging, then heavier surging, then surging so hard it dies.

No matter no much I back the throttle off, it never catches up. This is why I feel it's electrical/ignition.

I replaced the ballast resistor, condenser, and coil.

The plug wires, cap and rotor, and points are the only things I haven't replaced. And they are all the original parts from 1985. I'm starting to feel like either the cap and rotor are failing when they get hot.

We had the boat out today, the ignition switch failed when trying to start it after it died. Put the ignition lead directly to the main battery wire to the switch, and started it with the starter wire. It still ended up dieing on its own right when I got it on the trailer. So I'm under the assumption that the switch isn't the issue.

The boat dieing, is very very consistent. It literally dies in the exact same spot after we leave the marina. And it starts to die the same way every time. The only thing that let's the boat run for another minute on plane is to let it die and sit for a few minutes. Then it can idle out of the no wake zone/cove, and run for under a minute before it starts to spudder to it's death

I have an electric fuel pump on the boat pushing over 40 gallons an hour.

 

[Fitz98]

I had a similar issue on my 2000 Mercury Optimax 200, it was a low pressure fuel pump. Started out where it would die and after it cooled down a little, I could get it started back up. Got progressively worse until it would not start up again and had to get sea towed back to dock.
Not sure if you have any additional pumps other than main fuel pump.

 

[Donald]

Well I would replace the cap, rotor and points at least, maybe the wires also. They are due.

But another possibility is the gas tank anti-siphon valve inside the tank. It prevents gas from running into the bilge if the gas line broke. Try a hose into a 5 gallon container of fresh gas. The anti siphon might not be allowing much gas because its jammed or junk in the gas tank is clogging it. Also gas tank vent clogged.

Water in gas tank that gets sucked in when the boat is at a certain angle getting on a plane?

 

[mk378]

"On plane" seems to be the issue here. The pickup in the gas tank could be sucking air when the angle of the boat changes. Or otherwise starving for gas. If you look down the carb when it is running at throttle, you may be able to see gas coming out the jets. See if it slows down when the engine starts to falter.

During a time while it won't start, check the spark. That would rule out the ignition.

 

[hemitom]

check rubber gas lines if you have any and fuel filters , lines maybe soft and collapsing under high load , or restricted fuel filter.

 

[Driz]

You never said what motor type size year it is. Doesn't get you much info

 

[eljefino]

Originally Posted by mk378

During a time while it won't start, check the spark. That would rule out the ignition.


Should be able to run a timing light inline with a cylinder. Those lights are all over goodwill for $2.

I'm also a fuel thinker.

 

[leroyd92]

Fuel pump is new, and I filtered the fuel from both tanks while it was flat on the driveway for a couple days. Transferred 20 gallons of gas from one tank to the next. Cleaned out a lot of silt and never lost fuel fuel prime unless the tanks are empty

Both anti siphon fittings on the boat work and flow plenty of fuel.

They both are also 3/4 full.

 

[leroyd92]

The boat was sitting at the dock at idle after we started it in the marina, so it took 3 minutes to get to the dock, and after 3 minutes it sputtered and died. So I truly don't feel it's fuel related.

 

[leroyd92]

This is a Volvo Penta 290a

GM 350. 290 hp, quadrajet carb, Carter vane fuel pump rated at 57 gph

 

[philipp10]

I would do two things: Bring a timing light with you and watch the spark on one plug. It will change if it is electrical. Secondly, bring some starting fluid. Give it a pump when the motor starts surging. I would also change out at least the cap and rotor right away. Original from 1985? Wow.

 

[Silverado12]

Surging sounds like a fuel pump issue to me.

 

[walterjay]

I go with fuel. Especially on a boat.

 

[leroyd92]

Ok. So, even though It will die a few minutes at idle in the slip, you all still think it's fuel related?

 

[Warstud]

Rebuild the Carb

 

[Dinoburner]

The easiest thing to check when it dies is spark. We carry a center electrode busted out of an old spark plug in the ammo can tool kit. Just stick it in a spark plug boot and hold it close to the engine block with insulated pliers while cranking engine. Be very careful around the engine bay making sure there are no gasoline leaks.. Checking for gas in the carb has already been covered here. Of course there is a fire extinguisher close by.

 

[leroyd92]

I did, no different in issue

 

[leroyd92]

I guess I forgot to mention in all of this out I didn't specify that when the boat dies, it immediately starts again.

So i know for certain it's getting spark after it dies for 5 to 10 seconds, probably even before then

 

[mk378]

My leading theory along with most of the others here is that it's getting spark all the time but starving for gas. Though it isn't helping to have those 30 year old spark wires cap and rotor. Sparks jumping out of the main coil-to-cap wire to ground can cause this, although it's usually not very predictable.

So seriously just replace those and maybe you'll find it works. If not you're going to have to go out and do some more testing. In addition to actually watching the spark and fuel, you could disconnect the supply line at the carb, point it into a container and turn the key on to see what the flow is like. On a test drive, as soon as it starts to sputter pull the throttle back to idle and see if it can keep running.

An interesting thing about a points ignition system is that there is more current flowing at low speeds.

 

[RogerBacon]

Could it be a vent issue on the tanks. If air can not get in, fuel can not get out.