'84 175HP miss at idle

[RobsTV]

1983 Evinrude E175TRLCTD

Best way to describe it is, on muffs at 1100 RPM, thru the prop exhaust goes ba-ba-ba-ba-ba-pompf-ba-ba-ba-ba-ba-pompf.
The pompf repeats fairly regularly about every 3 to 4 seconds.
Slightly higher puff of exhaust smoke is also emitted during the pompf.

History.
New thermostats. Temperature perfect.
Runs great, but would be hard starting after hot. Wanted to stall. Had to choke/primer it if I wanted it to start hot right away. This in water that was 83F or higher. If idling in no wake zone for a while, RPM's needed to be kept up near 1000RPM, otherwise it might pompf and stall.

Compression 90PSI on all cylinders.
Can run WOT for extended periods, 5400 RPM's, pushing Wellcraft V20 at 43MPH, so seems great running at speed.

Did decarb a couple times. No difference.
Rebuilt carbs. They looked great, but did them completely anyway. No difference.
Performed link and sync.

Now testing in 70F water, and after a good 60 minute open water test run, ending with 15 minute river idle speed, checked spark plugs and all looked great except #1, which was blacker than the rest. Replaced all spark plugs with new UL-77V. #1 coil looked like a black tar substance on block touching coil, so thinking coil might be leaking (even though substance was dry), I replaced #1 coil. Again, no difference.

Using a grounded test light probe, while running on muffs at 1100 RPM, poked through each boot at plug, and it seemed that #1 grounding nearly eliminated the pompf, while the pompf was still seemed to be present grounding each of the other cylinders. Leads me to think it is something related to #1.

What do you think I should check next?
Thanks.

 

[Gary H NC]

Re: '84 175HP miss at idle

I still think you have an ignition problem. I would get a spark tester and make sure it will jump a bright blue spark across a good 7/16th gap.
Look in engine faqs on posts that explain doing the ohm and other tests on the coils and power packs.
A good factory service manual explains it well.

 

[RobsTV]

Re: '84 175HP miss at idle

Thanks for the reply.

Forgot to add.
To test for bad wire, switched spark plug wire that was on #1 with #4.
The problem seemed to stay with #1, meaning plug wire is probably O.K.

I will try to test for spark quality using a better method. Now that each plug boot has a tiny hole from probe, (as expected), there does seem to be a good spark jumping out of hole to test probe as it gets close. I will not be leaving the boots like this, only to test.

I'll swap the two power packs to see if the miss moves to other bank.

 

[tashasdaddy]

Re: '84 175HP miss at idle

sound good to me. better to trouble shoot, than throw parts at it.

 

[Gary H NC]

Re: '84 175HP miss at idle

Did you switch the just the wire around or the whole coil? Try swapping the coils and see if the problem follows..

 

[HighTrim]

Re: '84 175HP miss at idle

First thing you need to do is get a boot kit to repair them. They will come with a new plug spring as well, in case yours are corroded or rusted. Remove the old ones, but back the plug wire, leaving enough to still reach the plug, trim back about an 1/8 of an inch of insulation, fold over the exposed wires, insert the plug spring into the wire, wrapping the exposed wires around the pin. Slide new boot back over , you may need the help of some lube for this. Add grease to inners of boots. After that, you need to do a spark check like Gary said. Get yourself an inline adjustable spark tester, available at most auto parts stores for about 10 bucks. Set the gap to 7/16 of an inch, and make sure the spark jumps this gap with a strong blue ZAP!! After that , you will know better what you need to do next. Let us know what you find.

 

[Joe Reeves]

Re: '84 175HP miss at idle

A dry fluffy black looking spark plug usually indicates weak ignition or a continuity problem. Since you've alreday replaced the coil, check the continuity between the spark plug boot assembly and the coil end.

Also check for a lean running carburetor. Remove the carburetor face plate and have the engine running at an idle, the rpm where the engine is spitting back. One carburetor throat at a time, stick two fingers into the throat, acting as a sort of manual choke.

Should the lean problem cease to exist when sticking your fingers into one of the throats, that carburetor is running lean and the idle jet will require replacing or cleaning unless there is some other problem related to that particuular carburetor such a a bad seal to the intake manifold etc.

There was another problem in that year area whereas the intake was slightly warped at the manifold to crankcase area. Installing two intake manifold gaskets will cure that problem if it exists.

 

[guy74]

Re: '84 175HP miss at idle

Hi,
I had a very similar problem on my 1989 Evinrude 100hp. It was running lean at idle on #4, had the poof every 3-4 seconds. I took the air box cover off and found that if I covered the idle air orfice for#4 with my finger, it would run much better. I determined that the gasket on the top of the carb was leaking air into the idle circuit for that cylinder. If I sprayed a little penitrating oil on the gasket the motor would pick up and idle better for a little while. According to the PO the carbs were rebuilt last fall, but the gaskets on the idle pasages on top look pretty old. I wonder if they didn't take them apart and replace the gaskets. I hope this helps.
Sincerely,
Brian

 

[RobsTV]

Re: '84 175HP miss at idle

Thanks for the tips. I'll try them out Friday and post back results.

Plug wires are fine. They are not the piece together type, but are one piece, factory assembled. I forget the brand off hand. Yellow in color, and might say Magnum or something similar. Coil came with the piece together type of wire, but I hate them, and current wires measured fine with my Fluke.

Original coil installed was 0582106, and replaced with Sierra 18-5176D.