Coil issue when hot??

Greetings,
I am still trying to get my 4.3 LX/Gen II+ dialed in. I still have some sort of bogging issue....I am leaning towards the coil or something that is affected by high engine heat.

-starts very easily and idles great with no smoke

-after an extended run (10-15 mins), when you come off of plane it will spit and sputter at about 2000 RPM (and the RPMS will drop and act like it wants to stall) and then when you pull the throttle back it will idle back to 700 RPM.

-I can throttle past the sticky area and it will run fine.

-WOT, oil pressure, operating temp and top speed are good. All fuel filters have been changed/inspected.

-the spark plugs have been changed and the new ones have been checked and they look fine...maybe a hair lean.


Now, it SEEMS that if I run the bilge blower that the problem seems much less of an issue. If I run for 20 mins., the engine will completely stall when I come off of plane. So, that makes me think it is a tempature issue in the engine compartment. The vents are on the BACK of the boat so I think the design is bad...but that is just a thought.

Is the problem I am describing sound like a coil issue? I was thinking it was a carb issue for the longest time, but it does not happen all the time....very frustrating.

Sometimes it after I put in the water and I run it, the boat will do "its thing" and then run like freaking top for the rest of the day. Odd odd odd.

Any suggestions will be much appreciated.

Thanks!

Re: Coil issue when hot??

Ayuh,... I think you're still fighting a Fuel Delivery Issue....

The coil would Not cause these symptoms...

Re: Coil issue when hot??

I dont know what you have tired but here is what I would do.
Get tools and buddy, promise beer as a reward.
Take a OB tank and bulb and hook it straight to the carb and go out out on the water, the buddy is for pumping the bulb as a fuel pump. Run the boat as you have been and see if the issue remains. Have him pump the bulb as needed to keep the fuel full in the carb.
If the issue goes away, swap the bulb to the fuel pump and try again. Keep running the OB tank and lines. Then after each run add a piece of the old fuel system until the problem starts again then replace that piece.

If the fist time you still have the same issue then there is an electric issue and you can start looking there.

Like Bond-O says, I too think its a fuel issue.

Re: Coil issue when hot??

Well, I cannot argue that. My guess is that I am in need of a carb rebuilt then. I will drain the tank at the end of the season and make sure that is squeaky clean too.

I guess I was leaning away from the fuel delivery issue because it runs so well most of the time. It really seems that after it heats up is when the problems are found. Maybe my new fuel (last year) pump is starting to go....

Re: Coil issue when hot??

Well, I started at the fuel tank and quickly saw that the anti-siphon valve was missing. This was quickly replaced. There is no way the lack of the anti-siphon valve would cause any performance issues is there? That is only a safety device or am I wrong about that?

Re: Coil issue when hot?? **possibly resolved**

Re: Coil issue when hot?? **possibly resolved**

Well, the next thing I checked was the fuel vent. I have one of those setups that vent right to the fuel filler cap (no seperate vent). Anyway, so I pulled the vent and gave it a little blow and it was blocked. I gave it a little stronger blow and something let go and now the vent is free and clear. I am guessing there is no one way valve down there for the vent.

I bet this is what would cause my fuel starvation issue (as I was told). At idle the boat did not use enough to cause the issue to form. But, under power it must have.

I sure hope that was my issue. Now, I just hope whatever was in there gets caught by one of the filters before it causes a carb issue.

Hopefully today I can get the boat out in the water and test it.

Re: Coil issue when hot??

Sounds to me like the coil. When it acts up put your hand on the coil. Mine is smoking hot. If you cool the coil it runs perfect. Did you change the coil or electronic ignition? These two need to be insync. There needs to be a resistor or like 9 volts going to the coil. To much causes overheating and overheating causes these symptoms.

Re: Coil issue when hot??

Hopefully today I can get the boat out in the water and test it.

Click to expand...

Good luck, let us know what happens.

As for the anti siphon valve. I really have no idea what are intended for. That piece as never made sense to me. There is no reason to have one to keep fuel from draining back into the tank, because as soon as you start the engine the pump will pull it back up, and if they are a safety issue then I cant figure out how fuel draining back to the tank is a problem.

I took mine out long ago and have no ill effects from it.

Re: Coil issue when hot??

Anti-siphon valves do just that, if the feed line ruptures the fuel will not siphon out of the tank into your bilge. If the tank is lower than the rest of the fuel system then the valve is not required

Re: Coil issue when hot??

Bond-o is a boat GOD. You told me months ago it was a fuel delivery issue....guess what, it was a fuel delivery issue. That boat ran top notch today. It was a glug of crap in the fuel tank vent.

You da man.

Thanks.

Re: Coil issue when hot??

....guess what, it was a fuel delivery issue.

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Ayuh,.... Glad to hear it worked out for ya,....
Even more Glad to hear the comeback/ final chapter/ diagnosis/ Cure...

and if they are a safety issue then I cant figure out how fuel draining back to the tank is a problem.

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Like sqbtr says,.... It's another 1 of those things that keeps yer boat from goin' BOOM....

Re: Coil issue when hot??

bifflefan said:

As for the anti siphon valve. I really have no idea what are intended for. That piece as never made sense to me. There is no reason to have one to keep fuel from draining back into the tank, because as soon as you start the engine the pump will pull it back up, and if they are a safety issue then I cant figure out how fuel draining back to the tank is a problem.

Click to expand...

It is not there to keep fuel from draining INTO the tank. If any portion of the fuel system is lower than the TOP of the fuel tank, and leaks, it will siphon the gas from the tank and dump it into the bilge.

bifflefan said:

I took mine out long ago and have no ill effects from it.

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...and you won't have any problems until it goes boom

Do yourself a favor and reinstall an A/S valve.