Boat starts perfect but shuts off after 20 mins of driving

[carrie laws]

Ok im losing my mind hope someone can help, heres the story. Got a older boat for a great deal its in great shape in and out and motor looks so clean. But its been sitting for a few years. Knew it would take a lil work to get it going , but did new plugs, oil change, new fuel filter , and new thermostat, battery she had a lil old gas could not get siphoned so put fuel cleaner in it and seafom and new premium gas in. After a couple attempts she fired right up and purrs like a kitten, idles great , starts on the turn of the key and sounds perfect. Problem is after 20 mins on the water throttled the motor shuts off , will run fine on muffs though . like the key just shut off, no sputter no warning, then after about half hour or so it will start up or if i use starter fluid after a couple trys will start , Changed ignition coil, distributor cap and rotor, checked for water in fuel or gunk in filter there is none!! Changed the filter on carb, it had some debri in it but that didnt change the problem either , changed the fuel line from hard line to a rubber one thinking it was getting hot and vapor locking but it still shuts off while driving, What else could it be. Also another thing is my rpm guage says its at max. But the engine clearly is running at the right rpms. Maybe thats a bad rpm guage not sure. And not sure if that could be causing this issue??? One other thing when i got the boat it had no battery so when i put the new battery in. I hooked the black cable to negative and red to postive but i have 3 other cables not sure where they go??? One is all black i put that on the negative terminal found that was my issues to why all my lights and horn didnt work, but i dont know where the other two cables go. When i test them they seem to be positive , but im reading different answers of what these colors are , one cable is black with a yellow tip. One is black with a blue tip???? Could these cables not being hooked up be my problem. I will attach pic of cables. Somebody help????

 

[tpenfield]

What motor does the boat have? We need to move this thread to the proper forum.

 

[Scott Danforth]

How old is old gas?

Fuel cleaners won't work

 

[Bondo]

Ok im losing my mind hope someone can help, heres the story. Got a older boat for a great deal its in great shape in and out and motor looks so clean. But its been sitting for a few years. Knew it would take a lil work to get it going , but did new plugs, oil change, new fuel filter , and new thermostat, battery she had a lil old gas could not get siphoned so put fuel cleaner in it and seafom and new premium gas in. After a couple attempts she fired right up and purrs like a kitten, idles great , starts on the turn of the key and sounds perfect. Problem is after 20 mins on the water throttled the motor shuts off , will run fine on muffs though . like the key just shut off, no sputter no warning, then after about half hour or so it will start up or if i use starter fluid after a couple trys will start , Changed ignition coil, distributor cap and rotor, checked for water in fuel or gunk in filter there is none!! Changed the filter on carb, it had some debri in it but that didnt change the problem either , changed the fuel line from hard line to a rubber one thinking it was getting hot and vapor locking but it still shuts off while driving, What else could it be. Also another thing is my rpm guage says its at max. But the engine clearly is running at the right rpms. Maybe thats a bad rpm guage not sure. And not sure if that could be causing this issue??? One other thing when i got the boat it had no battery so when i put the new battery in. I hooked the black cable to negative and red to postive but i have 3 other cables not sure where they go??? One is all black i put that on the negative terminal found that was my issues to why all my lights and horn didnt work, but i dont know where the other two cables go. When i test them they seem to be positive , but im reading different answers of what these colors are , one cable is black with a yellow tip. One is black with a blue tip???? Could these cables not being hooked up be my problem. I will attach pic of cables. Somebody help????

Ayuh,..... Welcome Aboard,..... As noted, We've gotta know what motor, 'n by whom, as well as the vintage of it,.....
A serial number is a big help in Id'n it,....

 

[carrie laws]

What motor does the boat have? We need to move this thread to the proper forum.

Sorry i forgot to add that its a 84 celebrity boat with inboard. It has the mercruiser 260 5.7

 

[carrie laws]

How old is old gas?

Fuel cleaners won't work

Was told the boat was sitting 3 yrs but it hasn’t been stickered since 2016 so im sure its been longer then 3 yrs. Got the boat off the original owner he was a 85 yr old man so his years may be a lil off. There wasn’t alot of gas in it maybe about 5 gallons but i added one of the best marine fuel cleaners to it cause couldnt get anything to siphon out. Also here is the pic of those battery cables !

 

[dingbat]

Problem is after 20 mins on the water throttled the motor shuts off , will run fine on muffs though . like the key just shut off, no sputter no warning, then after about half hour or so it will start up or if i use starter fluid after a couple trys will start , Changed ignition coil, distributor cap and rotor, checked for water in fuel or gunk in filter there is none!! Changed the filter on carb, it had some debri in it but that didnt change the problem either , changed the fuel line from hard line to a rubber one thinking it was getting hot and vapor locking but it still shuts off while driving, What else could it be.

Checked fuel pump operation?
If OE, your looking at a 40 yro fuel pump. Certainly suspect

One is all black i put that on the negative terminal found that was my issues to why all my lights and horn didnt work, but i dont know where the other two cables go. When i test them they seem to be positive , but im reading different answers of what these colors are , one cable is black with a yellow tip. One is black with a blue tip???? Could these cables not being hooked up be my problem. I will attach pic of cables. Somebody help????

Obviously "aftermarket" (PO) additions to the electrical system.

Connectors are not to "code". Wouldn't bet a penny on proper color codes being used either.

Having said that, black is ground. The wire with the yellow insulator looks to be black. The other, hard to tell what color it is. Need to trace the circuit to determine polarity

 

[carrie laws]

Checked fuel pump operation?
If OE, your looking at a 40 yro fuel pump. Certainly suspect

Obviously "aftermarket" (PO) additions to the electrical system.

Connectors are not to "code". Wouldn't bet a penny on proper color codes being used either.

Having said that, black is ground. The wire with the yellow insulator looks to be black. The other, hard to tell what color it is. Need to trace the circuit to determine polarity

Yeah i was wondering maybe could be fuel pump going bad. Its just weird though cause it will sit and run on muffs for a hour but put it in the water and throttle down runs great for 20 mins then engine just shuts off. Tested spark everything got spark. But when you try to start back up it will fire but not fully start acts like its flooded for a good 30 minutes then will fire back up. As for the cables not sure if those need to be connected to anything. The one cable all black did connect that figured it was a ground and when i did all interior lights and exterior started working correctly and horn. But tested those other too cables and they seem to be hot don’t wanna connect to battery and do any damage if they aren’t needed or aren’t In correct places but im at a loss as to why this boat runs great and then just shuts off

 

[carrie laws]

Yeah i was wondering maybe could be fuel pump going bad. But do here it kick on Its just weird though cause it will sit and run on muffs for a hour but put it in the water and throttle down runs great for 20 mins then engine just shuts off. Tested spark everything got spark. But when you try to start back up it will fire but not fully start acts like its flooded for a good 30 minutes then will fire back up. As for the cables not sure if those need to be connected to anything. The one cable all black did connect that figured it was a ground and when i did all interior lights and exterior started working correctly and horn. But tested those other too cables and they seem to be hot don’t wanna connect to battery and do any damage if they aren’t needed or aren’t In correct places but im at a loss as to why this boat runs great and then just shuts off

 

[Scott Danforth]

You will have to manually/mechanically clean the fuel system

There is no shortcut. There is no mechanic in a can

 

[carrie laws]

You will have to manually/mechanically clean the fuel system

There is no shortcut. There is no mechanic in a can

I never said there was. But this stuff had been proven to clean the tank and gas almost all boat mechanics use it when winterizing and spring tune ups. Im not worried about that anyway im trying to figure out the issue of the boat shutting off!!!

 

[nola mike]

I never said there was. But this stuff had been proven to clean the tank and gas almost all boat mechanics use it when winterizing and spring tune ups. Im not worried about that anyway im trying to figure out the issue of the boat shutting

The point was that carp in the tank can be causing your issues, and if you had debris in the carb filter it's probably in the carb. Assuming you don't have a water/fuel filter. As for this miracle fuel cleaner, please share with us--especially any proof of efficacy. How did you check for water in the tank? Wonky tach can ground out ignition, but you say you're getting spark

 

[Grub54891]

Tachometer not working. Disconnect it completely, see if it helps. If a tach is bad it will cause running issues.

 

[carrie laws]

Tachometer not working. Disconnect it completely, see if it helps. If a tach is bad it will cause running issues.

Ok i will try that i was kinda wondering if that could cause any issues

 

[KJM]

If those loose wires are live then either find out where they go or at least tape them up and secure them so they are not moving around and occasionally touching ground and shorting something out.

 

[carrie laws]

The point was that carp in the tank can be causing your issues, and if you had debris in the carb filter it's probably in the carb. Assuming you don't have a water/fuel filter. As for this miracle fuel cleaner, please share with us--especially any proof of efficacy. How did you check for water in the tank? Wonky tach can ground out ignition, but you say you're

If those loose wires are live then either find out where they go or at least tape them up and secure them so they are not moving around and occasionally touching ground and shorting something out.

Yeah i did tape them up so they aren’t touching anything , boat still cut out after doing that. This weekend i am gonna try to trace down where they come from.

 

[KJM]

If the engine runs great and then suddenly dies, it sounds more like an electrical problem then an old/dirty gas problem. As said above, the tach sounds like a possibility.

 

[KJM]

Another thought is that the tank isn't venting and creating a vacuum after running a while. Try loosening the gas cap and see if problem goes away.

 

[carrie laws]

If the engine runs great and then suddenly dies, it sounds more like an electrical problem then an old/dirty gas problem. As said above, the tach sounds like a possibility.

I was starting to think that cause after it happened again the other day and I tested for spark and everything got spark and seems to be getting the fuel. Im also kind of wondering if it isn’t electrical i will go through the wiring today and see where those other two cables run to and and disconnect the tach And run it this weekend see if that fixes it. And if it does it again will try loosening the gas cap

 

[bbook83]

Put your new fuel hose in a remote tank or gas can, if you can do so safely, and run it on the water. If it does not shut down, you can isolate the problem to the fuel tank and fittings. If it does, keep looking.