470 3.7L Electrical help needed

nwboater45

Petty Officer 3rd Class
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Sep 6, 2012
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91
1989 Mercruiser 470, 165, 3.7L

First of all let me start off by stating that I am an electrical moron (half joking). I can handle mechanical I can handle but electrical drives me nuts. So anyways I was installing a Petronix ignition today with horrible results. I read several posts on this site and other sites in regards to intalling the Petronix ignition. So I disconnected the negative from the battery and installed the ignition. I reconnected the negative to check the voltage from the purple resistor wire. The purple wire after the choke was 10 and before the choke was 12. So I disconnected the negative from the battery again to splice in the new power per the posts I have read. I got all that done and was rechecking the volts again to make sure I had everything correct. Well I must have hit a ground wire or done something wrong when I heard a strange noise (like "phist") and the volt meter went to zero (oh ****). So I turned the ignition key to the first position and nothing worked on the dash. I then turned the key all the way and the motor turns over but of course won't start. Doesn't anyone know what I might have blown? Or even where to start looking? Like I mentioned electrical is not my thing. I did not see any smoke or smell burnt wire. Any suggestions will be helpful.
 

alldodge

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Re: 470 3.7L Electrical help needed

You spliced in new wire from where to where?
 

nwboater45

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Messages
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Re: 470 3.7L Electrical help needed

Nevermind. False alarm (well kind of). The ignition fuse blew. I didn't realise this controlled the intrument panel. The old fuse was tough to read so I am assuming it is 20amp. Replaced it and it started right up. I had to reset the timing a tad but it sounds good and the restarts while hot are turn key with no gas.

AllDodge, just to respond to your question. Petronix requires 12 volts going to the coil so what I have read on this forum is to tap into the purple wire upstream of the choke. So this is what I was working on when I blew the fuse.
 

alldodge

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Re: 470 3.7L Electrical help needed

Glad it all worked out. I was hoping that is what you did in the wire replacement but it wasn't clear what took place, hence the question
 

BrianD1973

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Sep 7, 2010
Messages
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Re: 470 3.7L Electrical help needed

How did you check/set the timing? I just did the same Pertronix Ignitor 2, Flamethrower 2 upgrade and wanting to check the timing and the boat manual has zilch about timing... I guess if I had a service manual that would help.... No hoses to unhook or anything I would guess, so just hook up light to #1 plug wire and where should mark be on flywheel? Guessing distributor has an adjustment nut and I'll turn her till she's in the right spot once engine is warmed up with muffs running?
 

stonyloam

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Mar 13, 2009
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5,830
Re: 470 3.7L Electrical help needed

Merc 470 right. The timing mark in on the rotor. It is a groove, so you should be able to find it. I took some white paint and painted the groove. Hook up the light to #1 and set the timing to 4 degrees BTDC. Set the idle to about 600-650. Distributor rotates clockwise (turn CCW to advance timing).
 

BrianD1973

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Re: 470 3.7L Electrical help needed

Thanks Terry... sorry to hijack :-( and I actually rewrote my post because I hit the "reply to thread" instead of post quick reply underneath after typing out just about the same question.... and wiped the old post out.... in it I stated it was a 170.... my bad AGAIN! lol And I actually did find a little info in the specs in the manual... guess there is a difference between the 470 vs. 170 because it states 8 degrees... and did find the groove :) chalk does help... Huge thanks! now, I have to hit the right button!!! ;-)
 

nwboater45

Petty Officer 3rd Class
Joined
Sep 6, 2012
Messages
91
Re: 470 3.7L Electrical help needed

Brian, no worries on the hijack. You are correct with the manual stating set the timing to 8 degrees. There was a service bulletin issued from Merc switching it to 4 degrees. Follow Terry's advice on painting the groove white it will be a huge help. I have in the past even painted the tick mark on the indicator white as well.
 

BrianD1973

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Sep 7, 2010
Messages
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Re: 470 3.7L Electrical help needed

hmmm, so even on the 170 it should be 4 degrees??? (and if the 170 and 470 are the same thing, why didn't they keep the designation the same?) anyhow, Thank you Sirs for your help... you are much appreciated... will change it in the morning if 4 is the correct degree.... was at about 15 deg when I started.. not sure if just changing from the merc coil and pertronix ignitor to the ignitor 2 and flame thrower 0.6 ohm changed the timing or it just somehow over time had moved since someone else checked it.... guessing that is why it stalled a couple times in the past year or two... or possibly the coil going bad... think I checked it a year or so ago and it was at 8.... and just was having a brain freeze tonight... did the bulletin stating the timing change to 4 deg. explain what the reason was?
 
Joined
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Messages
3,028
Re: 470 3.7L Electrical help needed

hmmm, so even on the 170 it should be 4 degrees??? (and if the 170 and 470 are the same thing, why didn't they keep the designation the same?) anyhow, Thank you Sirs for your help... you are much appreciated... will change it in the morning if 4 is the correct degree.... was at about 15 deg when I started.. not sure if just changing from the merc coil and pertronix ignitor to the ignitor 2 and flame thrower 0.6 ohm changed the timing or it just somehow over time had moved since someone else checked it.... guessing that is why it stalled a couple times in the past year or two... or possibly the coil going bad... think I checked it a year or so ago and it was at 8.... and just was having a brain freeze tonight... did the bulletin stating the timing change to 4 deg. explain what the reason was?

Here is the service bulletin, was lowered to make up for today's crap fuels:
 

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nola mike

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Re: 470 3.7L Electrical help needed

The 470 had a few name changes and minor differences from year to year, but all the same 3.7l merc block and ford head...
 
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