Mercruiser Starting Problem

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This problem is killing me! I have a 1987 I/O Mercruiser 3.7 liter 4 cyl 165 HP engine that refuses to turn over. 3 weeks ago I installed new points, plug wires, filters, oil, & grease. The engine started and ran beautifully. This week, however, I turn the key switch and nothing happens. I have charged my batteries, checked my one large breaker, and checked fuses. I used a jumper to short the large terminals on the slave solenoid and the engine fires up and runs nicely. I replaced the slave solenoid and got the same problem. If I can't work this out soon, I'm thinking about installing a push-button switch that will short the slave solenoid to start my engine. Any ideas?
 

Bondo

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Re: Mercruiser Starting Problem

Do you have power coming from the Key Switch to the Exciter Wire on the Solenoid ?????
 
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Re: Mercruiser Starting Problem

Yes, I do. I have 12.5 Vdc on the small terminal on the left (wire comes out of harness that goes to control console)when the key is in either the "on" or "crank" position. I also have 12.5 Vdc on the small terminal on the right (wire comes from pos side of ignition coil) when the key is in either the "on" or "crank" position. I fthe slave solenoid operates the way I think it does, I would need 0 Vdc on one of the two small terminals to cause a votage drop and the solenoid to actuate. Is that correct?
 

Blk-n-Blu

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Re: Mercruiser Starting Problem

loranimal, Is it possible there is another safety switch holding out the ignition, like the tilt/trim or an emergency cutoff.is the coil shorted to ground? You might try raising the outdrive all the way to trailer position and then lower it all the way down and see if that helps. Just another $0.02
 

hoot

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Re: Mercruiser Starting Problem

my wiring diagram and engine (165hp,IL6) is wired slightly differently. i am thinking that you should not have 12.5 on the small terminal at the on position. this solenoid is used for starting only. for it to work, it has to get 12.5 volts on one side and the other small wire goes to GROUND. this causes the solenoid to kick in and the larger terminals supply more current to the starter. i have no wire attached from my + coil to this solenoid that i can see. i have a wire to the distributor and one to the starter, and my kill swithch also.
 

kcole683

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Re: Mercruiser Starting Problem

You should have 12 volts to the s terminal on the slave selenoid when key is in start position.<br /><br />The metal frame of the slave selenoid is grounded that is where the selenoid gets its ground. The other small terminal on your selenoid is a purple wire to the ignition coil,this wire bypasses the resistance wire circuit for starting.<br /><br />If you put 12 volts to the s terminal and ground the case the selenoid will click in and make contact,if it does not you have the wrong part or a bad part. If you put 12 volts on the S terminal and ground the other small terminal and it kicks in then you have the wrong part.<br /><br />NAPA does not carry this selenoid in the marine catalog. Sierra makes one, part nember 18-5802 $49.49 at west marine. Original Merc # is65057A1or65057T1.<br />The 18-5802 cross references to a selenoid that NAPA sells for about $15.00,it fits old Ford Trucks with points ignition. Works perfect on my 1985 3.7 Mercruiser. <br />Good Luck and have fun.
 
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Re: Mercruiser Starting Problem

Thanks for the info guys. Spark-chaser, today I was able actuate the slave solenoid and start the engine by grounding the small terminal on the left (the one with the yellow and red wire) Unless I physically use a jumper to ground them, the two small terminals continuously have 12 volts on them, in the start and crank positions. Is that correct? Are you USCG or USN?
 

kcole683

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Re: Mercruiser Starting Problem

I am not sure of wire colors but you should have 12 v on the yellow red start wire only when key is in start position.(disconnect from selenoid to test).<br />You should have a purple wire on the other small terminal which should be dead until the selenoid engages. It will get 12 v at this time from the positive on the big terminal.<br /><br />To test selenoid,remove from boat and connct s to 12 v pos. and 12 volt neg.ground to the frame of the unit. If it does not engage you have a bad or wrong part.<br />They make alot of selenoids with the same frame that are grounded through the second terminal and not the frame.<br />When you get the right part check for blown fuses from you grounding out.
 

hoot

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Re: Mercruiser Starting Problem

found a wiring diagram close to your system. your solenoid should be grounded back to the battery by a metal frame attached to the solenoid, not a terminal. there may be a wire attached to the frame or solenoid for this. one small terminal (s), is fed from the key and the (I)terminal goes to the coil. looks like you are grounding thru a post, =wrong part. i still don't understand why you have 12v in the on position at this solenoid. seems like the starter would be engaged all the time. check for loose wires and nuts holding wires on. does the new solenoid look just like the old one?
 

kcole683

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Re: Mercruiser Starting Problem

Sounds like an echo in here here here here here here here...........
 

hoot

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Re: Mercruiser Starting Problem

hey, i hear it too, too, too, too, too...<br />hope we have helped this guy out and not confused him.
 
Joined
Jun 22, 2004
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Re: Mercruiser Starting Problem

Thanks again guys. I installed a push button today to provide a ground to the slave solenoid. I know! I know! It's a jerry-rig, but I would have to create a major catastrophe to get into my console and wire trace, and I want to get the boat in the water ASAP. I ran the engine for 15 minutes with no problems and started it with the switch 4 times with no problem. I'll permanently fix the problem this winter. Yes, the new solenoid looks exactly like the old one. I'm embarrassed to say that I'm an electronics tech. and what should be a relatively simple problem is kickin' my butt! Thanks for all of your insight guys.
 
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