5.0 shuts off randomly and has a mind of its own

[ktyamaha36]

I have a 1995 Bayliner with a 5.0 mercruiser. The boat has always ran great and never giving me a single issue since Ive owned it. I have installed a edelbrock intake, and brand new 4 barrel carb about 6 months ago.

The Tach stopped working one day when I was out. the next trip out it worked again. Now its not working at all, But did not seem to affect the engine running.

This weekend while out in the gulf idling, the engine died. Verified the carb was getting fuel, checked spark and had none. Found a fuse had blown. Boat ran great all the way back to the canal (20mins at about 35mph). as soon as I came into the no wake zone and brought it to an idle , within 15 seconds it died again. Checked fuse again, still good. The engine turns over but would not fire off. Got towed it, let it sit for about an hour and tried it again, fired right off. Let it idle for over 30 mins at the dock and finally shut it down for the night. This morning I went to start it and it wouldnt fire off. After tapping the coil, double checking wires, pumping fuel into the carb via accelerator pump, somehow I got it to fire off. Now im scared to take it out..lol

Can the tach be causing this? Im thinking its either that or the coil? How can I test the tach to see if its any good?
Should I just replace the coil? or do they either work or dont. I feel like somthing is shorting out randomly.

Any tips would be great.

Thanks guys

 

[Silly Seville]

Re: 5.0 shuts off randomly and has a mind of its own

The tachometer is just that...a meter (or visual display) of an electrical signal. The tach cannot "send" a signal to the engine to make it run or not run.

I think you are looking in the right direction with the coil however. When they over heat, the electrical continuity breaks down, and the engine can exhibit erratic running conditions.

 

[ktyamaha36]

Re: 5.0 shuts off randomly and has a mind of its own

OK thank you.

I believe someone has removed the Thunderbolt ignition off the engine and switched over to a conventional set up. Do both systems use the same coil? Id hate to fry a brand new one,

 

[Silly Seville]

Re: 5.0 shuts off randomly and has a mind of its own

By conventional, do you mean an automotive based system? If that is in fact the case, you should get the correct parts reinstalled before using that boat again. The Thunderbolt system works perfectly fine...I can't imagine why the PO would remove it for something of lesser quality and perhaps compromising the boats safety. Let's see some pictures of your setup.

 

[makonnen]

Re: 5.0 shuts off randomly and has a mind of its own

Yes, pics please.

And check out this thread
http://forums.iboats.com/showthread.php?t=551252

 

[ktyamaha36]

Re: 5.0 shuts off randomly and has a mind of its own

The mechanic who installed the new bellow boots and trim sending sensors told me someone had removed the thunderbolt system. It still has the "mercruiser brand" coil on it, and it looks to be the same distributer that the thunderbolt system uses. It has a rectangle style plug on the rear with a harness plugged into it. But I do not see a "Brain box" anywhere .

We are getting pounded with rain by this tropical storm today here in Florida, so I wont be able to get pics until tomm.