Ignition problems still??? Maybe?

[snlgraham]

My first post so please be patient. <br />140 mercruiser, 16ft trihull, 181 4-cylinder, 1980, 2-barrell rochester carb. Boat runs awsome for 20 minutes or so then it cuts in and out and looses power. As I make bee line for the dock it eventualy dies out. Can restart with throttle way up but it runs like crap and will die when put in gear. Before I found this forum I rebuilt the carb, changed out the fuel filters, new roter, points, condenser and plugs. After reading several posts here it looked for sure to be the coil. I changed it out and had to get more plugs cause they fouled again. In the driveway it ran great and set the timing exactly at 6 degrees. It even idled decently. Then on our big Memorial day outing it started its same old thing. I was so ticked and flustered that I hit a sand bar while trying to idle in to the dock . No damage from the sand. I did notice that when it acts up the volt meter shows 9.5 volts and normaly shows 13 volts. Is this the coil agian? Would a bad alternator do this? What do I do next??

 

[lilmandavis]

Re: Ignition problems still??? Maybe?

check all connections and trace the voltage drop out

 

[snlgraham]

Re: Ignition problems still??? Maybe?

I have checked all connections on the engine. Are there connections under the dash that could do this?<br />How do I trace a voltage drop?

 

[paulrfrancisco]

Re: Ignition problems still??? Maybe?

Disconnect the positive cable from the battery while running and see if it continues to run.. if not, its a bad alternator or regulator. Also, do you charge the battery somehow overnight or when not using the boat? If you dont, does the battery voltage show normal when the key is only on, but not running and then drop only when the problem occurs? Or does it start out low?

 

[snlgraham]

Re: Ignition problems still??? Maybe?

Thanks Paul, I will give that a try tonight when I go to the lake. It is in a slip there.<br />The battery did show normal voltage and seems to be recharging ok from the alternator. I know this because I ran the battery down in trying to restart last week and it charged right back up after only 20 minutes. Where is the regulator? What does it look like?

 

[chelle]

Re: Ignition problems still??? Maybe?

I NEED A WIRING DIAGRAM FOR 4.3 MERCRUISER FOR THE FUEL AND IGNITION SYSTEM <br />ANY ONE HAVE ANY IDEAS WHERE TO FIND ONE

 

[DayCruiser]

Re: Ignition problems still??? Maybe?

Could need a new wiring harness. My voltage meter would drop and be jumpy during long outings. Turns out there was a short in one of the wires.

 

[snlgraham]

Re: Ignition problems still??? Maybe?

I disconnected the positive battery cable while running as Paul suggested. I was idling at the time and the engine quit. I did notice that the voltage drop is only when at slow rpms. Like at idle. When rpms are over 1000 the volts go right back up to 13volts. I pulled the alternator off and will have it checked tommorrow. <br /><br />Any one know, is the voltage regulator built into my alternator?

 

[bamadave]

Re: Ignition problems still??? Maybe?

chelle, please start a new thread. It's impolite to bust in on a thread in progress. thanks

 

[thunderroad]

Re: Ignition problems still??? Maybe?

snlgraham...I'm not sure what year the break was when they went to internal regulators in the alternators. How many wires are there on the alternator? If the alternator checks out ok, it's likely the regulator that's bad. If it has an external regulator and even if the alternator checks out ok, I would seriously consider switching to a one wire alternator with the regulator built in and eliminate the external regulator. I just did it on mine and the new style alternator didn't cost any more than a new transistor regulator was gonna cost. Got rid of a component and a few wires in the process. VERY simple to hook up. Just the main power wire and a ground wire and you're done. Not sure if the alternator is the total cure for the problem you describe but it does sound like you do have some sort of problem in the charging system. You say it died but you were able to start it back up with the throttle opened up. It would seem like if the charging system wasn't working and the battery went completely dead to the point of killing the engine, you wouldn't have been able to start it back up. Hard to say though...electrical systems can do some pretty weird things.

 

[rodbolt]

Re: Ignition problems still??? Maybe?

folks, DO NOT ever ever remove the battery cables on modern altenator whith the engine running, I see at least 1 a month that someone tried that age old stunt.<br /> usually sets them back 250 bucks before I get to hunt for the original issue.<br /> most modern electronically controled altenators may survive the intitial dissconect but sometimes die on the recconect.<br />most electronic systems use a battery reference for regulation. guess what happens when the battery is removed from the circuit ?<br /> there are many ways to test the issue at hand, most will require a DVM.<br /> do you have one ?<br /> if so then hook up the meter from the coil +primary tower and ground and go run it, once it starts acting up did the voltage change significantly from running good ?<br /> we are not chasing specific numbers we are using common sense.<br /> if for instance you had 9V running fine sucking a soda and its starts choking and you look at the DVM and its at 6 volts we know there was a significant change, if no significant change we just eliminated a lot of chasing.<br />the inverse is true as well.<br /> say it ran well at 9V and runs crappy all of a sudden but its moved to 12V. gives another spot to look.<br /> like I harp, this aint rocket science it just requires some reading and understanding of how and why the ign coil works at all.

 

[snlgraham]

Re: Ignition problems still??? Maybe?

Thanks guys for the input.<br />I had a tech check the alternator and it was working fine. The tech thought that there might be a short in the wire harness.<br /><br />rodbolt- I don't have a DVM but I do have a cheep analog multi-meter I keep in my box. Will that work?

 

[snlgraham]

Re: Ignition problems still??? Maybe?

Put the alternator back on this evening. I started poking around the wire harness. No obvious shorts or breaks but I did find it was saturated with 30 weight. The privious owner had replaced one of the trim pump lines with nylon hose. Needless to say it was pissing all over everything! Maybe that oil has made a short in a connection somewhere. Too dark to continue......And that thing called work is always getting in the way of my projects!

 

[DayCruiser]

Re: Ignition problems still??? Maybe?

Yes, mine was a short in one of the wiring harness plug ins. I could wiggle it and the voltage regulater would jump to where it was suppose to be(no fuses) I told the mechanics this but they went through every wire anyway and charged me over 300$ labor. But maybe they prevented something down the line. Always trying to think positive

 

[snlgraham]

Re: Ignition problems still??? Maybe?

Get this!! I was towing my boat home in the dark last night. Pulled it out so I can work on this problem. On the way home, the alternator on my suburban went out and I was towing with trailer lights on, only on my battery for power! We made it back. If its not one thing its another!!!