Mercruiser 4.3 LH won't fire

[cretch]

Had an incident with the boat today. Put the boat in the water without the plug. We caught it before the water got very high. The water got just to the bottom of the engine and might have touched the bottom of the starter. The boat died. We were able to install the plug and pump the water out ok. The boat now turns over just fine, but will not fire. The carb is getting gas as we can see it spraying in the carb. This is on a 4.3 LH Mercruser. Is there any thing that might of shorted out that is causing the boat not fire?

 

[alldodge]

Serial numbers are best but even a year helps. Assuming this is a LH and not a LX it might be a 1998 model

Start with the basics and see if you have 12V on the + side of the coil?

 

[cretch]

Yes it is a 1998. I'm at work right now, but yes, I plan on checking that tomorrow. Thanks.

 

[cretch]

My Manual has a couple of numbers that appear to be serial numbers. One is 4-211015LS and the other is 0L011748

 

[alldodge]

0L011748

This would be correct of a 98 LH

 

[achris]

My Manual has a couple of numbers that appear to be serial numbers. One is 4-211015LS Model number and the other is 0L011748 Serial number

If you confirm no spark, then run through the TB-V diagnostics flowchart.... It can be found at the end of this post...

http://forums.iboats.com/forum/engi...-mercruiser-thunderbolt-ignition-systems-work

Chris..........

 

[cretch]

Chris
Thank you. That info looks to be very helpful.

Cretch

 

[cretch]

So today I removed the distributor cap and inspected the terminals. The distributor that was on was the original from 1998. The contacts on the inside looked pretty bad, so I replaced the Distributor cap first. When this didn't fix it. I went thru the trouble shooting flow chart that Chris provided in his link. It indicated a bad Ignition Sensor. I plan on picking up a new one maybe tomorrow. Everything else seems to check out ok. Hopefully this fixes it.

 

[cretch]

Update: I purchased a new ignition sensor and installed it. Boat still would not fire. Backed up and rechecked everything we could think. Pulled the coil wire from the distributor and re-verified it was getting a good spark by plugging a spark plug onto it and grounding the plug as we turned it over. Had a nice blue spark. Pulled the plugs on at a time and did the same thing. Sometimes we got a spark, and sometimes we didn't. It wasn't consistent like it should be. Went back to the Marina and picked the guys brain again. He was stumped too. We had spark and fuel, but no ignition. He finally went into the back and brought out a new coil and said to just take it and try it. If it fixed the problem to come back and pay for it. If not, just return the coil. To my surprise, it did fix it! Even though it appeared to be putting out a good spark, apparently it wasn't strong enough. Lesson learned I guess. Thanks to those who responded.

 

[alldodge]

Glad its running, but if it does it again, pull the gray tach wire off the coil

 

[cretch]

What does that do?

 

[alldodge]

The tach gets the rpm signal from the negative side of the coil. If the tach is shorting out it will kill spark and therefore the motor. Can either remove the wire at the coil or the back of the tach

 

[cretch]

Where is the tach located? Are you talking about the Tachometer on the dash?

 

[alldodge]

Where is the tach located?

If you don't have a tachometer then this is a non-issue

 

[cretch]

If you don't have a tachometer then this is a non-issue

Yes I have a tach. I wasn't sure if it was the tachometer you were talking about. Thanks, I'll try to remember that if this happens again.