engine turns but no spark... is it my coil?

[tuanp]

I just bought an 85 Sea Ray with a 170hp Mercruiser 4-cylinder. The boat has been sitting for several years when I got it; I'm now trying to get it started. The starter cranks and the engine turns but it does not start because I'm not getting sparks out of the plugs. The distributor looks almost new, so I'm focusing on the coil.<br /><br />When I connect my multimeter between each terminal on the coil and ground (engine case) I get 12V. So 12V between the positive term and ground, between the neg term and ground, and even between the center node (that connects to the distributor) and ground. This is while the key turned to ON, but not yet on Start. I don't measure anything between the two terminals though, even when starting. I hooked up a light probe across the two terminals and saw no light when I'm starting.<br /><br />I'm thinking I should get 12V between the two nodes, but I'm not. Can I conclude that the coil is bad? Any ideas what's causing the lack of spark?<br /><br />By the way, when I say I'm getting 12V, I really get only 11.x or 10.9x. Is this normal?<br /><br />Thanks in advance for any help.

 

[Trent]

Re: engine turns but no spark... is it my coil?

Several things to check...I dont think its your coil. Remove all wires from your + side of the coil. Put a jumper wire from the + side of the battery to the + side of the coil and try to crank. If it does you will need to remove the wire to make it stop running. If it still does not run.. remove the (I belive they are grey wires, its late) from the - side of the coil and retry. Come back and let us know. Im tired. Second shift is a pain

 

[KiLer]

Re: engine turns but no spark... is it my coil?

Check the gap on your points. also take a look at the contacts to be sure they're not fouled.

 

[airman]

Re: engine turns but no spark... is it my coil?

Doesn't sound like the coil to me either, although I wouldn't rule it out. When I started my 470 (I think that's what you have) for the first time in 3 years I got no spark either. I solved it by jumping from the positive side of the coil straight to the battery. I also had my truck parked close up beside the boat and jumper cables hooked up (truck's engine running at a fast idle). As soon as hooked up the jumper the boat started right up. I ran it for a minute or so then diconnected the jumper and it has started fine ever since.

 

[airman]

Re: engine turns but no spark... is it my coil?

Two other points. 1 - You shouldn't read 12v across the coil. That would indicate a bad coil. 2 - 10.9 volts is normal. There is a resistor built into the "run" wire going to the coil to drop the voltage a bit. That wire is supposed to be bypassed during starting to give a better spark with the heavy starter load on the battery. That's what the other wire to the coil is for. Also, if the engine hasn't been run in 5 years, keep a close eye on the temp. The impeller in the leg is likely past its prime.

 

[tuanp]

Re: engine turns but no spark... is it my coil?

Ok, from the responses in this thread and others, I figured that it's the points and replaced them. Sure enough, it started right up - after sitting for 6 years! Amazing!<br /><br />What's not so amazing though, is that after I let it run for about a minute, went to get the wife, came back and tried to start it again. But this time, the engine fires but has trouble starting, or would start, run rough for a few seconds then quit.<br /><br />Tomorrow, I'll replace the plugs first. Looks like one of the plugs is not firing because it's wet when I removed it, while the other 3 are dry. I'll check the spark-plug wires too. What else should I do to revive this thing from hybernation?<br /><br />I want to replace the impeller also, as suggested, but I don't know where it is. Is it near the engine or on the outdrive? Do I have to drop the outdrive? I sure hope not. Don't know if this makes a difference, but this engine has fresh water cooling.<br /><br />One more thing, during the 1 minute the engine ran, I noticed water coming out of one end of the long cylinder that has water hoses coming in and out of it (two large hoses and two smaller ones); the heat-exchanger I'm guessing. The water came out and spilled into the bilge, along with some steam or smoke. Doesn't seem normal to me. Is it? Any ideas here?<br /><br />Thanks all for your help. Sorry for all the questions; I have so much to work on. This forum has been so helpful so I want to take advantage of the knowledge that's here.

 

[Spidybot]

Re: engine turns but no spark... is it my coil?

Tuan, have you ordered a manual, yet? Sure would allow you to make better use of your time.<br /><br />Most of your problems over the last two weeks could have been looked up and you'd have all the specs and tips handy.

 

[airman]

Re: engine turns but no spark... is it my coil?

That long 4" tube on the port side of the ebgine is the heat exchanger. The boat was probably stored without draining it first and it froze inside. You might get lucky though - those end caps are like frost plugs and they bend out rather than breaking (happened to me once too). Pull them off, pound them flat and put them back on with Form-a-Gasket or something similar. While the caps are off, flush it out with a hose. The impeller is in the lower leg. You don't need to pull the leg off. Split the leg at the seam. Drain the oil first. I think there's 6 bolts plus the zinc to remove first. When you refill the leg with oil you need to get the pump and fill it from the bottom up.