Mercruiser 470 possible electrical problem

[deanehorn]

As I am cruising, at fairly low speed (2000rpm) for maybe 20-30 minutes, the starboard engine suddenly shuts off with no warning. Seems to be running fine while running. After engine shuts down, it will not restart until it sits for 15 minutes or so. I even tried spraying starter fluid in the carborator, and it just turns over with no intention of starting. After sitting and then started, it will run for another 2 - 10 minutes before shutting down again. The port engine has shut off unexpectedly in a similar manner but it will restart immediately and then continue to run. The port engine seems to be a little on the hot side according to the temp gauge. Any ideas on why the engine might be shutting down?

 

[JB]

Re: Mercruiser 470 possible electrical problem

Moving to I/O

 

[llerrad]

Re: Mercruiser 470 possible electrical problem

What kind of engine, size, electrics, points or eletonic. Need more info.

 

[arboatdr]

Re: Mercruiser 470 possible electrical problem

Sounds loke you are losing your fire. When it does it agian check for 12 v to the coil with the key on. Look the coil over for oil film. Check the points. Sounds like the coil or coil wire breaking down under load. I've heard of condensers breaking down under a load but i think thats rare. DH

 

[Northern Eclipse]

Re: Mercruiser 470 possible electrical problem

If its running hot on the gauge chances are the voltage regulater is getting hot, these are water cooled on these motors, these are not cheap to replace if you cook 'em. These motors are closed cooling and also need to have the heat exchangers cleaned out often ( a least once a season salt water) maybe 2 seasons fresh. Are you losing any antifreeze or having to top the coolant? When was the last time you has the impellers changed in the outdrives?

 

[deanehorn]

Re: Mercruiser 470 possible electrical problem

Thanks for the response...<br /><br />I just bought the boat, the seller said he had the outdrives serviced a couple of years ago.<br /><br />This is a fresh water application.<br /><br />470 Mercruiser, 170HP, 4 cylinder, has points, 1986 boat, port and starboard side engines.<br /><br />I swapped the coil between the starboard and port engine, so it will be interesting to see next outing if the problem follows the coil. I'll check the 12volts across the coil with the key on as was suggested next time this occurs.<br /><br />I may buy a couple of new condensors to be safe as suggested. And I'll look into cleaning out the heat exchangers as suggested.<br /><br />There is some antifreeze in the bilge, but the coolant is topped off, and I don't see any leaks or overflow when running. It may have been spillage from the winterization people??<br /><br />I need to get my shop manual out again, but I guess the voltage regulator supplies voltage to the coil?

 

[mkast]

Re: Mercruiser 470 possible electrical problem

Next time it happens, disconnect the tach at the coil, Mercruiser manual troubleshooting steps.

 

[airman]

Re: Mercruiser 470 possible electrical problem

The coolant may be coming from the water pump weep hole. It's a common problem for these engines. Search this site for the fix if that turns out to be your problem.

 

[deanehorn]

Re: Mercruiser 470 possible electrical problem

Thanks! I've got plenty of things to look at now. I may take it for a cruise Sunday -- with volt meter in hand. I'll give you an update if I make it out Sunday.

 

[MrBill]

Re: Mercruiser 470 possible electrical problem

Bonus Room:<br /><br />Trent provided the forum with this link about the 470 and 3.7L coolant leak issue in the past...I've saved it and used it many times. This offers and excellent explanation and repair instruction. But you might not like the answer....<br /><br /> http://www.sterndrives.com/470information/470coolantleakrepair.html

 

[deanehorn]

Re: Mercruiser 470 possible electrical problem

I swapped the coil between the two engines, and the problem followed the coil.<br /><br />Right after the engine stalled, I measured continuity from the (-) of the coil to the (-) on battery and got discontinuity (without removing any wires). After sitting (maybe cooling) for a while, continuity "resumed" between the coil (-) and battery (-) and I was able to start the engine.<br /><br />In hind site, I should have disconnected the (-) coil wire and checked continuity from the wire to battery ground since with the wires connected, I really don't know what I was measuring continuity between.<br /><br />I'll replace the coil next weekend and give an update.

 

[Trent]

Re: Mercruiser 470 possible electrical problem

You should have checked for voltage at the (-) side of the coil. Using the positive lead of the voltmeter to the (-) side of the coil and the (-) voltmeter lead to the battery ground. You should have 9 volts min. While cranking you should have 12 volts min.<br /><br />But since the problem followed the coil you know where your problem is.