AAAARRRRGGGGHHHHH, it(39)s back!!! Twin Motor Running Issue-gctid363629

[Guest]

Well after 4 months of perfect running, my issue is back all be it with slightly different symptoms. Start my starboard motor, runs perfect. Simply turn the port motor key on (not crank motor) and the starboard motors stops. Start the port motor, runs perfect. Try and start the starboard motor and it just cranks and cranks, no start.

So I check for spark. What I find is that when the port key is turned on ( again not cranked), I loose spark to the starboard motor. Now just to complicate matters more, this only happens when the motors are hot. 3 times on the weekend the motors ran perfectly from cold start. Planed out without issue. Problem occurred when I brought boat off plane. Starboard motor splutters and dies, will not restart while port motor is running. Switch port motor off and starboard motor fires right up. This happens 3 times, so cannot be a coincidence.

This is doing my head in. I'm thinking my 1st fix it to swap out the coils as that is all I can think of that may be effected by heat. At least this is a fairly cheap starting place.

Any thoughts?

[yachtman]

What did you so last time to fix it?

[JimMc]

The shutting down when turning the key on the opposite engine says it's clearly electrical.

Look at the wiring what's common ?

Voltage to each engine ?

Ground connections ?

[Nikko]

Just a thought - but it sounds like it may be low voltage to the primary side of your ignition - and since it's heat related and apparently RPM related - I'm thinking you have a bum charging circuit on one of the engines or It's also possible you could have a bad 12v resistor wire (or ballast resistor if so equipped) to the primary side of the coil as well...

I'd fire the port engine, hold a meter on the port 12VDC feed to the port coil, and have someone turn on the stbd key. Based on the problem you describe, I'd expect to see that voltage drop or disappear as the engine quits. If you do, work your way backwards "up" the wiring by disconnecting various pieces of the circuit. Hopefully that will start to give you a clue....

[2850Bounty]

Ian, by chance has someone changed the OEM wiring so that both helms are powered via the same battery bank?

IOW, if you power up the Port side engine via it's battery bank, does the Stbd side helm light up also? And/or visa-versa?

I don't yet know what this could mean, and I'll wait to hear your answer.

I'm having a difficulty seeing how one engine would affect the other with regard to ignition alone.

[yachtman]

Before you go buying parts and switching out coils hot wire the coil to the engine that wont start. If it runs than the problem is in the wiring circuit. If it still doesn't run after hot wired and all electrical is isolated from each engine then it's in the coil ballast resistor or distributor.

One question. I read an earlier post of yours about ballast resistor questions. Are you sure you got the correct ones?

[Guest]

Here is the previous post from the last time I had this issue.

http://www.baylinerownersclub.org/forum/showthread.php?65932-Twin-Motor-running-issue

After consultation with Mallory, removal of the installed ballast resistors fixed the issue. Yes they are still removed.

Yes, Rick both motors start off the cranking battery bank. I only have 1 MBSS.

Yachtman, how do I "hot wire the coil to the engine"?

Nikko, I think you may be on the money. This was happening last time. Removal of the ballast resistors allowed more current to flow and the motors ran fine, BUT I remember the current still dropped. So I'm thinking this may be the cause. Now I gotta find the solution.

My boat is an hour and half away from home. I am going down Wednesday to try and diagnose. Keep the suggestions coming and I'll try what I can to find out info on Wednesday.

Thanks for your input.

Ian

[yachtman]

To hot wire an engine. Take a wire from a known well charged battery and disconnect the power wire from the coil. Connect the wire from the charged battery and put it where the power wire to the coil was. Than start the engine. Note that the engine wont shut off until you pull the wire off the coil. If all runs fine then you have a problem in the power circuit . If it doesn't run fine then its in the coil or the distributor. You can run the boat like that you just can't shut it off with the key. Make sure the wire is of sufficient size.

Also don't leave the wire connected for long periods of time with out the engine running. Its like leaving the key on and it can heat up your coil. Be careful of sparks as you know in a boat bilge. You can use the boats battery as long as it is charged and doesn't have an excessive draw in it. IE... a bad power circuit. Don't run the boat with the boats battery with out the alternator connected it could fry the alternator.

Its a simple process really.

This process only works ins no run situation. It runs now then run it until it breaks down be ready to install the hot wire immediately upon breakdown and that is how you eliminate where the problem isnt

[2850Bounty]

epoc wrote:
Well after 4 months of perfect running, my issue is back all be it with slightly different symptoms. Start my starboard motor, runs perfect. Simply turn the port motor key on (not crank motor) and the starboard motors stops. Start the port motor, runs perfect. Try and start the starboard motor and it just cranks and cranks, no start.

The bold text is what has me puzzled.

Ballast resistor or no ballast resistor, with the Stbd engine running, and when the Port engine key ONLY is turned on, there should be NOTHING capable of drawing enough current to affect the running of the Stbd engine.

Key ON only does not makes sense, even if both are sharing a common cranking battery.

Now.... if this only occured during cranking the Port engine, I'd look towards a heavy cranking load that is somehow taking a Negative out of the loop for the Stbd engine... but where???

Or maybe a Positive current path out of the loop....., but again, where and how large would this need to be????

So I'm going to suggest that the actual battery cabling at the two engines is NOT the problem.

I'm more inclined to look at the harness connectors or something in the OEM harness that leads to the instrument panel and back to the engine.

Have you located the engine harness/helm harness interface connections and pulled them apart and examined them????

Your ignition circuits are in this harness, along with all other engine data circuits.... and the helm Pos/Neg!

Look for a harness connector near each helm perhaps at the rear of the instrument panel!!!!!!

Pull these apart also, and examine the connections.

If bad and failing, the current draw may not be all that great, but yet enough to foul up the ignition voltage to either engine.

Meanwhile the starter motor solenoid circuits are apparently left unaffected since they both crank just fine.

.

[yachtman]

I have had a no start situation at various times in my life on different boats.

If you have a bad connection or some thing corroded it can draw power away from the coil and the engine wont fire because there is no electricity left even though it cranks fine. Usually I have found it to be in the starter(drawing too much power) a starter solenoid key switch or in bad cable connections. Some times the battery cables can corrode from with in and you can't really spot it. Another thing you might do is a starter draw test.

[Guest]

Yes Rick, I have pulled and sprayed the main harnesses before. I will try this again. Thanks Yachtman. Will suss these things on Wednesday and report back.

Regards,

Ian

[2850Bounty]

Ian, I'm due for an Australian vacation!

[JimMc]

Maybe the real issue is wiring at the helm.

[Guest]

2850Bounty wrote:
Ian, I'm due for an Australian vacation!

It'd probably work out cheaper than hiring a mechanic here Rick!

[Guest]

JimMc wrote:
Maybe the real issue is wiring at the helm.

Don't think so as it happens exactly the same at both upper and lower helms.