165 mercruiser coil problems

[megamog]

I have an 84, 165 mercrusier. The problem is that I keep burning coils. sometimes they last for hours sometimes 30min. it seem to happen at high speed more then low. here is a list of things I have tried:<br />changed coil<br />changed resisters<br />added new resistors<br />new ground<br />new plugs, caps, rotors, condenser, points, wires.<br /><br />I have tried running it at my house with no results and I have ran it at the dock with no results. happens when I am out for awhile.<br /><br />here are a list of things I have heard that could be wrong, I am just wondering what you guys think.<br /><br />Exhaust problem--but I had no rust on my spark plugs to back it up<br /><br />water in my gear oil in the stern drive- it does seem to be watery. not sure how that would cause the coil to go

 

[searay3]

Re: 165 mercruiser coil problems

Water in the gear oil - not coil related<br />Plugged exhaust - could cause performance issue, but not coil related. Have to use a volt meter or analog and check power at the coil, points open, key in run position. If more than approx 7 volts, wiring issue. Might need a coil with built in resistor. If 7, check again in start position (key). Should be battery voltage. There is more than one type of coil, make sure you have the proper type for your points system.

 

[searay3]

Re: 165 mercruiser coil problems

Also, if the gear case oil is watery (milky), best have it serviced. Big bucks (1000+) if it goes.

 

[megamog]

Re: 165 mercruiser coil problems

it hasnt run since last year so the oil looks like oil but I get a slight hunt of water. When I turn it over tomorrow I will check it again.<br /><br />I just got the same advice from the marina where I live. TY

 

[Don S]

Re: 165 mercruiser coil problems

oil looks like oil but I get a slight hunt of water

What is a "Hint" of water?????

 

[megamog]

Re: 165 mercruiser coil problems

in run I have 12.24V at battery<br />10.43 at coil +<br />0.23 at coil -<br />no tach connected.<br /><br />i am not sure right now if the points where open or closed. going to try to find some specs on it

 

[megamog]

Re: 165 mercruiser coil problems

well I seem to reacll someone saying I dhould switch to an electronic pick up instead of points. This way I could control the electricity for the coil much better. The coil itself would also be cheaper to replace.

 

[megamog]

Re: 165 mercruiser coil problems

Well here I am and it is 2010. Still no luck. I blew through those coils. I have moved to a new city. My neighbor works for ford and was able to point me in a new area. Then another friend helped me to. Still doesn't run. I have now started a whole new wiring system and this time I am even upgrading my coil to a high performance grade. If it burns this time I am gutting the boat and putting in a new engine with all the trimmings. Will sell the old engin as a paper weight!!!!

 

[BigWally1]

Re: 165 mercruiser coil problems

With the older mercs you need an external resister for the coil or you will burn them up repeatedly.

 

[DJ]

Re: 165 mercruiser coil problems

With the older mercs you need an external resister for the coil or you will burn them up repeatedly.

Ditto. Any more than 10 volts, to the coil, will melt them fast.

 

[Bondo]

Re: 165 mercruiser coil problems

10.43 at coil

Ayuh,... You Should be seeing 7 to 9 volts...

 

[Don S]

Re: 165 mercruiser coil problems

When the engine is running above 2000 rpm, check the battery voltage at the battery and see what you get. With the 470 style charging system on your engine, you may be seeing 16+ volts, which will cook coils and batteries. Very common problem with that setup.