165 Mercruiser - no spark / low voltage

[tony dz]

Hey all.. I just bought a 1978 Mercuiser 165 inline 6.. I've had it out three times now.. the first time it started fine at first but after running it about an hour (and shutting down) it wouldn't start.. I kept trying and eventually it did. second time no issues.. third time it stalled coming into dock and wouldn't restart.. checked the plugs and discovered there was no spark.. based on what I read in other posts, I checked the voltage at the (+) side of the coil and I'm only getting 7.5 volts (not while cranking)... what do I check next?

 

[Don S]

Re: 165 Mercruiser - no spark / low voltage

You have a ballast resistor or a resistor wire that drops the voltage down to the coil, and your votage sounds about right.<br />But do you have spark to the spark plugs? That is the question. When was your last tuneup. Points, condenser, cap, rotor, actually setting the dwell and timing.

 

[tony dz]

Re: 165 Mercruiser - no spark / low voltage

When it quit on the water there was no spark at the plugs. We pulled off the cap and there was no spark at the points either. Surprisingly the points looked pretty good, no corosion. <br /><br />When I checked the voltage last night I didn't get a chance to re-check the plugs to make sure the problem hadn't fixed itself. I'll check again tonight. <br /><br />So, if 7.5 volts is ok at the coil and I'm not getting spark at the points (which look clean), is that pointing at the condenser? <br /><br />I just got the boat so not sure about last tune-up, but I know it sat for 2yrs.

 

[thunderroad]

Re: 165 Mercruiser - no spark / low voltage

Complete tune-ups on those motors are relatively cheap and do wonders for the peace-of-mind. I know...I've got a 69 model 160...I did a tune-up this spring before I ever tried to start it and considered it money well spent.

 

[tony dz]

Re: 165 Mercruiser - no spark / low voltage

Thanks Thunderroad.. so I'm clear.. what does a "complete tune-up" include.. is this the points, condenser, cap, rotor, dwell and timing" that Don S refered to?<br /><br />Related to that, is there any way I can rule out the coil as being my problem? I'll probably do the tune-up just for the peace of mind, but hate to have a bad coil come back to haunt me if that was the real problem. Coils are easy to replace, but hate to replace it if it's still good. The boat is already nickle and dimeing me.. but I guess that's what old boats are all about.

 

[thunderroad]

Re: 165 Mercruiser - no spark / low voltage

yeah..those things plus plugs and maybe wires. My boat had sat for 4 years when I bought it last spring. I did points, condenser, cap, rotor and plugs before trying to start it. I got it started, set the dwell and timing and waited until it got dark and restarted. There was spark arcing between the - post and the center of the coil so I replaced it. There was spark jumping between plug wires where they touched together near the dist cap so I replaced them. Have had zero spark related problems since. I replaced the points and condenser this spring just for the heck of it although I probably only ran the thing about 10 hours last summer.<br />Believe me, I understand where you're comin from on not spending any unnecessary cash.

 

[Rhadley]

Re: 165 Mercruiser - no spark / low voltage

I'd replace the plug wires also-they can be intermittent.<br /><br />And check all the battery cable connections, (not just at the battery post)especially if the cable has a screw-down clamp that connects the thick cable wire to the clamp.

 

[tony dz]

Re: 165 Mercruiser - no spark / low voltage

OK this is weird.. I'm in the process of changing the points, rotor, and compressor and noticed that the wire the connects to the compressor and points isn't connected to anything on the other end!!! It's just dangling!!! I assume this should be grounded to the block or somthing? Please help. <br /><br />Seperatly, I'm noticing the points I'm removing have a "felt like" pad the brushes against the rotor shaft. (like those tech terms?) anyhow, the new points I got from the marina, don't have this pad.. Is this ok???

 

[boathog]

Re: 165 Mercruiser - no spark / low voltage

points and condensor should be connected to the neg. term on the coil.

 

[tony dz]

Re: 165 Mercruiser - no spark / low voltage

thanks... it must have fallen off somehow.. how about the points.. do I need the felt pad? anyone?

 

[bluemist]

Re: 165 Mercruiser - no spark / low voltage

Yes. Felt pad is called an oil wick it lubricates the humps on the rotor as the points break. Put a new one on and give it a few drops of 30wt.<br />AL

 

[tony dz]

Re: 165 Mercruiser - no spark / low voltage

the new points don't even have a place for the oil wick..(there isn't a holder) does this mean I have the wrong part?

 

[thunderroad]

Re: 165 Mercruiser - no spark / low voltage

Possibly...do they look exactly like the ones you took off? I think there was more than one distributor possibility for that engine.<br />Sounds like you found your problem in the wire not being hooked up to the coil.

 

[tony dz]

Re: 165 Mercruiser - no spark / low voltage

Update: She's running, thanks for all the help! Not exacty sure which part was the problem, but I replaced coil, cap, rotor, condensor, & points and now she works. The loose wire thing was my goof.. I had taken a picture of everything before I started monkeying (just in case) The wire was properly attached in the picture, so I must have forgotten to hook it back up at some point during troubleshooting. It probably thew me off track a bit, but in the end I'm glad I replaced the parts anyhow.