electrical gremlin's

[RonR]

I have had this boat for about a year now. We have ran about a 1000 gallons through it with a lot of success. I am now having some sort of electrical gremlin and looking for a little guidance on where to start. Most times the engines turn right off like they should, other times one or both diesel (gas chevy 350's). All are fully tuned, plugs, cap, rotor, electronic ignition. Each are on the money for timing and run perfect. Each are showing around 550 hours now.
I also have a problem with the Port tack on upper and lower stations showing about 2k over actual rpm (compared to the flow scans that also show rpm/engines hours and fuel use. Sometimes the tacks are right sometimes not. Seams as if the tack is off it will diesel more often. I have disconnected the port tack feed to see if it still will diesel when turned off, makes no difference. For some reason I still feel like there is some kind of back feed feeding the dizzys as I have had this problem in the past with a car that had a bad tack. I have even tried turning off all power supply via main braker to all batteries, it still does it. Am I driving myself crazy thinking its a power feed issue and not some kind of carb issue?

Also each carb has been removed from the boat, fully tanked, cleaned and rebuilt. I did all the work myself and tuned them with a vac gauge per the Holley book. Under power the boat runs very well, no issues at all, temps are running around 160 for each. Each use about the same amount of fuel per the flow scans. No smoke, no oil burn, each reach the same rpm under full power and you can run at full power as long as your check book can keep up. Plugs are clean when removed to check for fouling.


I know its not good for the engines to do this, and its also embarrassing when you pull up to the fuel dock, shut it down and its dieseling.


(side note for the picture, no I don't run with my fenders out, no I don't pull a dink. We were sitting at the dock when we seen a green dink floating out in the bay, first thought was a fisherman was passed out or a medical condition. So we dropped the lines and ran out to check to see if everyone was ok.... it was just a lone dink that got away, so we towed it back to the dock. It was reclaimed the next day, I hope by the owner.)

 

[boomerang]

I have had this boat for about a year now. We have ran about a 1000 gallons through it with a lot of success. I am now having some sort of electrical gremlin and looking for a little guidance on where to start. Most times the engines turn right off like they should, other times one or both diesel (gas chevy 350's). All are fully tuned, plugs, cap, rotor, electronic ignition. Each are on the money for timing and run perfect. Each are showing around 550 hours now.
I also have a problem with the Port tack on upper and lower stations showing about 2k over actual rpm (compared to the flow scans that also show rpm/engines hours and fuel use. Sometimes the tacks are right sometimes not. Seams as if the tack is off it will diesel more often. I have disconnected the port tack feed to see if it still will diesel when turned off, makes no difference. For some reason I still feel like there is some kind of back feed feeding the dizzys as I have had this problem in the past with a car that had a bad tack. I have even tried turning off all power supply via main braker to all batteries, it still does it. Am I driving myself crazy thinking its a power feed issue and not some kind of carb issue?

Also each carb has been removed from the boat, fully tanked, cleaned and rebuilt. I did all the work myself and tuned them with a vac gauge per the Holley book. Under power the boat runs very well, no issues at all, temps are running around 160 for each. Each use about the same amount of fuel per the flow scans. No smoke, no oil burn, each reach the same rpm under full power and you can run at full power as long as your check book can keep up. Plugs are clean when removed to check for fouling.


I know its not good for the engines to do this, and its also embarrassing when you pull up to the fuel dock, shut it down and its dieseling.


(side note for the picture, no I don't run with my fenders out, no I don't pull a dink. We were sitting at the dock when we seen a green dink floating out in the bay, first thought was a fisherman was passed out or a medical condition. So we dropped the lines and ran out to check to see if everyone was ok.... it was just a lone dink that got away, so we towed it back to the dock. It was reclaimed the next day, I hope by the owner.)

Pull the coil wire off of the dieseling motor. If it quits you have an ignition problem. If it still runs, you might have a carbon buildup in the heads that keep igniting the incoming fuel/air.
Are the operating temps normal?

Edit: I see you said the temps are running 160 but I would still put a thermo gun on the head/block. Something is causing the stuff to light off if you don't have spark from the ignition.

 

[RonR]

Pull the coil wire off of the dieseling motor. If it quits you have an ignition problem. If it still runs, you might have a carbon buildup in the heads that keep igniting the incoming fuel/air.
Are the operating temps normal?

Edit: I see you said the temps are running 160 but I would still put a thermo gun on the head/block. Something is causing the stuff to light off if you don't have spark from the ignition.

Good idea on the coil wire and checking the temps with a gun.
Thank you

 

[High Wire]

You can swap tachs port for starboard to see if the problem moves.
Is this BOTH engines running on?
Could be the spark plugs are one range too high.
Could be carbon buildup. Use a good decarb spray and follow the directions exactly.

 

[RonR]

You can swap tachs port for starboard to see if the problem moves.
Is this BOTH engines running on?
Could be the spark plugs are one range too high.
Could be carbon buildup. Use a good decarb spray and follow the directions exactly.

I thought about the plugs as well on the last tune up. So I went back to the factory book that came with the 2006 Crusader engines and made sure the plugs were the ones recommended and they are. Not to say that one heat range cooler might help. I have not tried a carbon treatment. I really never thought any of them were true, just snake oil.

 

[FF]

"If it still runs, you might have a carbon buildup in the heads that keep igniting the incoming fuel/air."

This is a common problem that is easily fixed.

The easy way is to purchase a pump insect sprayer , a "flit gun".

With the engine warm increase the idle and simply spray a mist of water into the carb. Enough water so the engine stumbles but not enough to klll it.

You will have to advance the throttle to keep it running while stumbling.

About 5 min is all it takes.

If you wish to see it work, do it to your car with a newspaper under the exhaust outlet, the black chunks are carbon.

Just a dribble of water from a bottle also works but is harder to control.