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Failing Coil Problems? stalling when warmed up

D

dbrahms

Contributing Member
I have stalling isses on my starbord side 360. it seems to happen only when warmed up and after running a bit. I've stalled out at the dock, after backing down near idle speed when coming into a no wake zone etc.

yesterday, after 5-10mins of runnign at 3k RPM, the starboard gave up 500RPMs and then stalled. Limed back on one motor and after a while, tried the stalled motor and it started it up. Put it under load and then it stalled again. There is a brief period of roughness before it stalls. Waited another 10mins and it started up again and ran smooth but was careful not to exceed 1500 RPM. ran at low RPM without issue all the way back.

Also, carb is opening up just fine. when hot, it's wide open. carb was also rebuilt a year or two ago.

Lastly, not sure if this is related, but when at the dock, it's hard to start initially. sounds as if batt is dead although it's a new battery and is connected to a marine charge all week just like the other batt is for the port motor.

Could this be a failing coil?
 
Possibly. Why not swap the coils and find out? If the port motor screws up the same, toss the coil out.

On the hard cranking, that could be many things, but you need to eliminate the coil as a problem first.

Jeff
 
Jeff, would a bad coil affect the starter? When initially cranking over, it sounds like RRR...(pause)...RRR.....(pause). Then, something seems to "recover" and the starter seems to get a bit stronger. After running for a minute or two, i cna shut down and restart strong. I would likely still have the stalling issue after running under load a bit but either way, not sure if the coil could affect the initial cold start.
 
Uh-oh! You're getting water in the motor from the exhaust system--that's why the RRRR--hesitate---RRRR--hesitate.

Be very careful here or you can do some major damage. Let the motor sit overnight, then pull the aft spark plugs on either side (assuming you have log manifolds. Let me know if you have center dumps.) Ground the coil lead to the block (so it won't start) and crank her over. Pay strict attention to what blows out the plug holes--like water. If you see some, pull the exhaust off that side and start investigating.

Good luck!

Jeff

PS: If the side that's troubling you has swivel elbows, let me know. I have the cure for them.
 
No center dumps Jeff. regular log manifolgs which are 1 season old. this motor is new and has less than 40hrs on it so i'm suspecting a failed gasket.

Anyway, sounds like i have two problems here. The failing coil stalling me out under load after running a while and the initial weak startup caused by something else.
 
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Seeing you (and I) have log manifolds, the rear most plugs are the ones to pull to check for water intrusion. It's possible your manifold/ elbow gasket is leaking water into the system, so there's another place to check.

Note: Be sure to drain the block and manifolds BEFORE taking anything apart! If not, you'll have a lot of water getting in there.

Jeff

PS: Do you have swivel elbows? They're the type with 4 vertical bolts between the riser and elbow (that allow it to swivel for adjustment). These *%@^ things are notorious for leaking, and even when practically brand new. (One of mine leaked after a month or so.) I have the solution to that if yours is leaking.
 
Jeff - no swivel elbows here.

As for draining the water, i think there is a drain plug underneath the elbow. But as for draining the block, i assume you meant to pull the rear plugs and use a fluid extractor? that's how i was going to check for water in the first place. i dont have a down station so all i could do on my own is pull the plugs, stuff paper towels in the plug holes (very shallowly placed), pull the coil wire and turn it over a few times. If there was water on the paper towel, I thought that would confirm it. Or i might just tape paper towel in front of the holes so i dont get any paper in the engine.

Also, with the plugs pulled out, I assume there wouldnt be the RRR...RRR....hesitation.
 
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Have you checked the timing on that engine? This can cause the starter hesitation (vapor lock). I would try this first. Easy first step! I would then pull out all the plugs to check for water one side at a time. Forget the towels or rags if a cylinder has water in it you won't miss it! Watch cylinders while someone else cranks the motor. If all is new and tight I doubt water is the problem but you never no!

Boats are fun!!!

BOAT= B REAK O UT A NOTHER T HOUSAND!

Good luck!
 
With the plugs out there will be NO hesitation at all. Any water will blow right out the plug hole (unfortunately, blowing away your paper towels as well!)

If you can't recruit a helper, you can jump the starter solenoid at the motor and crank it over that way. Hook a wire to the "S" terminal on the starter, then touch it to the hot post that's right beside it. (I jump mine now and then with a set of pliers.)

On draining the block, there is a drain plug down low near the motor mounts on each side of the block, and plugs in the center of the exhaust manifolds. (There's also a drain plug down lower in the manifold for ??? purposes. Leave that one alone!)

Jeff
 
Just got back from the boat. No water in the rear cylinders. i pulled off one of the elbows too to check the condition of the gasket and it was fine. I replaced the one i checked since it was off anyway.

Also, i replaced to the coil as thats what i suspected the problem being. Took the boat out, fine at 3000rpm for 2-5mins (as it had been doing) and then when i stopped, turned around and throttled back up again, it runs rough and wont go to 3k RPM again. it goes up to 2k RPM and beyond that, it starts running rough.

Could this be a bad ballast resistor over volt-ing the coil? at 3k RPM, the gauge says 14v. at idle it hovers just under 11v. battery is new and alternator seems to be fine.

Also, to eliminate fuel problems, I am running 1 fuel tank to both motors so the fuel should be fine. i also replaced the fuel filter for the troubled motor and still having the same problem.

I also had the marina mechanie time the motor a week ago so that should be fine too.

HELP!
 
Jeff, what's your sollution to leaking swivel elbows? Would be nice to have in my back pocket should that happen on my 440's.
 
Are you sitting down? I clean the parts thoroughly--especially that stainless sleeve that goes between the parts--then I epoxy the whole mess together! Use epoxy like it was grease on the O-rings, and use it on that sleeve as well. The trick is to use SLOW epoxy (ah-hem!) and either assembe the parts in place (for proper alignment), or mark the parts so you can 'aim' them properly while assembling them at home.

Done three this way and the little b*st*rds have yet to leak.

Jeff
 
One of my co-workers just got back from the lake and had the same problem you are having. Both engines running off of one tank and then all of a sudden one of the engines loses rpm and dies. He found the following problem. Due to the ethanol in the fuel the gas line running to the engine is degrading. When it gets hot it constricts, cutting off the fuel flow. He started squeezing the line until he found the soft spot. He believes the ethanol and the fact that his fuel lines are 25 years old caused this problem. I may have the same issue, I found small particles in my carburators that may be my fuel lines degrading and not dirt from the tank.
 
jeffsboat said:
One of my co-workers just got back from the lake and had the same problem you are having. Both engines running off of one tank and then all of a sudden one of the engines loses rpm and dies. He found the following problem. Due to the ethanol in the fuel the gas line running to the engine is degrading. When it gets hot it constricts, cutting off the fuel flow. He started squeezing the line until he found the soft spot. He believes the ethanol and the fact that his fuel lines are 25 years old caused this problem. I may have the same issue, I found small particles in my carburators that may be my fuel lines degrading and not dirt from the tank.
Click to expand...


and did changing his fuel line solve the problem? I doubt this is my problem but worth a shot.
 
Yes it did. He actual saw the line constrict after working on the problem all day Saturday. Where I keep my boat also had to replace all the fuel lines on their small 18hp rental boats due to fuel lines degrading when they switched to ethanol fuel.
 
Hope the fuel line thing solves your problem, makes sence.

Jeff, thanks for the heads up on the @^%#$ swivels. Epoxy eh? different, but hey, if it works it works. Thanks man.
 
jeffsboat said:
Yes it did. He actual saw the line constrict after working on the problem all day Saturday. Where I keep my boat also had to replace all the fuel lines on their small 18hp rental boats due to fuel lines degrading when they switched to ethanol fuel.
Click to expand...

are you saying there is enough suction force from the fuel pump that it will cause a weakened fuel hose to essentially collapse under suction pressure?
 
Hi, I believe you too have a ballast resistor problem. I got the coil to cool down today by putting a two pole ballast resistor form the coil pos.post to the main ignition wire. My 360s are fairly new with 450 hours but since installation I've had the same problem with the starboard motor. This weekend I'm going to tear out the whole ststem and rewire.
Oh Yes. Check your Tachometer Wiring.
 
egg harbor 1977 said:
Hi, I believe you too have a ballast resistor problem. I got the coil to cool down today by putting a two pole ballast resistor form the coil pos.post to the main ignition wire. My 360s are fairly new with 450 hours but since installation I've had the same problem with the starboard motor. This weekend I'm going to tear out the whole ststem and rewire.
Oh Yes. Check your Tachometer Wiring.
Click to expand...

Why would the tach wiring cause any problems?
 
So, i replaced the ballast resistor and checked for a compromised fuel line. Still having the same problem. I think my coil is still being over-volted causing it to breakdown after a while of running at 3k RPM. At this speed, I am seeing 14volts constantly on the gauge.

So, i'm suspecting that although the ballast resistor was replaced, the wiring to it is bad making it useless.

Does the wiring for the resistor lead to the ignition key at all? Perhaps there is a voltage regulator that went bad?

What else could lead to over volting the coil?
 
Have you checked the voltage at the coil with the running? Should be about 7 to 9 volts. If it's 12 volts (or more) there's a wiring oops! someplace. If the voltage reads okay, then it should NOT change when running above 3,000 rpms.


Jeff
 
Saturday, i had the same stalling problems. Sunday, before leaving the docks, i checked the carb and saw that the chock was a bit sticky. i sprayed some pb blaster lightly around the linkage and moved it around a bit. it wasnt sticky anymore.

Could this have been the problem? My run on Sunday was flawless. I didnt bring it over 2800rpm but still, boat ran with no problems at all. Would a sticking choke cause stall outs when backing down to idle after a run at 3000rpm for a bit?
 
oh yeah,Would Micheal Phelps pass out if he just did the 2000 meter butterfly and he came up for air and you stranggled him

After you make your next run go and look to see if that choke is wide open,should be

Should be wide open after a few minutes of warm up
 
greasemonkey said:
oh yeah,Would Micheal Phelps pass out if he just did the 2000 meter butterfly and he came up for air and you stranggled him

After you make your next run go and look to see if that choke is wide open,should be

Should be wide open after a few minutes of warm up
Click to expand...


I think it opens up just fine but when going back towards idle and slowing down, it would stall out. figured that the choke would need to close a bit to make the mixture more rich but with it stuck open, it was could be running to lean near idle speeds? what do you think?
 
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