1985 90Hp Evinrude running rough at mid range.

[NCmiller]

Model: E90TLCOS

My 90hp is running rough around mid throttle, the range is just before planning and just before WOT (about 1500-3500 RPM). It idles good and will run WOT good. Problem is in the mid range. At times the problem will clear up, but issues will return. Sometimes it will bog down almost like one cylinder is not firing, but not very often.

What I have done this spring before running this season:
1) Replaced all fuel lines on engine.
2) Cleaned internal fuel tank, replaced tank fitting, all fuel lines, primer bulb, and fuel connectors.

After replacing all of above, engine at times will run rough around mid range. Here is what I have done on the engine at this time:

1) Checked Compression. 140 PSI all cylinders.
2) Replace spark plugs.
3) Ran on standard tank and hose.
4) Checked fuel vacuum before VRO pump. Good, <3 Hg.
5) Checked VRO output pressure. Good, 7 psi, dropping to 4psi when pump clicks.
6) Removed VRO pump and applied pressure at pulse input. It would only hold 5 PSI. Should pump up to 15 PSI and hold pressure. Noticed housing had a crack in it. Bad, pump is leaking.
7) Installed a used standard fuel pump from a blown 1979 115Hp.
8) Test ran engine and I have the same symptoms; idles good, runs rough at mid range, runs good at WOT. I thought I found the problem.

Kind of at a loss here, I have been thinking this problem is a fuel delivery issue but I am now wondering if I may have an ignition problem. I would like to get another point of view before I start troubleshooting the ignition system.

Thanks, Tom

 

[Toddboat]

Re: 1985 90Hp Evinrude running rough at mid range.

Possibly the low speed circuit in the carbs? I think, though, that the low speed circuit typically only transitions it from idle speed to very low speed, not all the way up to 3500 rpms. That part doesn't add up. Just seems like a fuel problem, though, because if ignition, it would probably be a problem at WOT as well.
I would run seafoam through it to decarbonize it and clean the carbs, then link and sync the carbs when reinstalling them to make sure that all of the butterfly plates open in snyc. They may only all be open the same amount when at WOT, but not at mid range rpms, thereby creating a condition where the cylinders are not getting equal amounts of fuel and air. Check first to see that all of the butterfly plates are opening in sync with eachother before going any further. This is, of course, assuming it's a carbureted motor. I'm assuming a 1985 model must be?

 

[NCmiller]

Re: 1985 90Hp Evinrude running rough at mid range.

Toddboat, thanks for the response! I'll check the linkage on the carbs, before I launch into the ignition system. I have been running the engine for 15 years, it was rebuilt by Tenkiller Marine (TMS) 10 years ago. They did a good rebuild job! There could be a chance something on the linkage is worn, lose or missing, I'll have to check that out. Motor has been running good up to recently. Seafoam would be a good idea to try. I am thinking about checking the output pressure of the used fuel pump this afternoon. The pump has been sitting up for a while and I would like to know if it is pumping OK.

 

[emdsapmgr]

Re: 1985 90Hp Evinrude running rough at mid range.

You did not get into the carbs, according to your first post. That carb does have mid-range jets. They will affect mid-range on that engine. Possible one or more of them are restricted. Time to pull the carbs down and remove the jets (idle, mid and high) Visually inspect each for possible debris. (such as bits of deteriorated fuel hose, etc.) Might as well clean them at the same time.

 

[NCmiller]

Re: 1985 90Hp Evinrude running rough at mid range.

emdsapmgr, last year I was having air in fuel issues and deteriated fuel lines. That is why I replaced all fuel hose and I cleaned and installed carb kits in the carbs. It ran good after the rebuild. But that was last year and you maybe onto something. Boat is in the water and I think I will be pulling her out tomorrow and going through the carbs again.

I mixed 3/4 can of seafoam in a gallon of pre-mix fuel. Took it down to the boat and ran some of that mix into the engine. Sprayed some seafoam into the cylinders too. Will let that sit over night and then spray some into the carbs while running. Don't think it will do much, so I'll run the boat around to the ramp and pull her out tomorrow after work. I'll check the linkage and clean the carbs.

Thanks for posting! Tom

 

[Daviet]

Re: 1985 90Hp Evinrude running rough at mid range.

You can use an inductive timing light to check the ignition system. Check each wire for constant and steady spark when the engine is acting up.

 

[NCmiller]

Re: 1985 90Hp Evinrude running rough at mid range.

Daviet, good idea. I just bought a self-powered inductive timing light. That will be a good use for it. Should have bought 4 of them one for each plug wire.

 

[NCmiller]

Re: 1985 90Hp Evinrude running rough at mid range.

While at the dock today, I started it up after the Seafoam sat over night in the engine. It smoked a bunch and after it warmed up I shot some Seafoam into the carbs causing the motor to almost stall. Then I shot enough in the carbs to stall the engine. I let is sit for a while and I started her back up. Was smoking a bunch and then I left the dock and ran her out in the river. I was still running on the gallon for seafoam/gas/oil mix. Seemed to run a bit better, but I still notice a miss in the mid range of the throttle. While slowly excelling to not quite on plain, the missing (shuddering) will begin. It seems to be more apparent when there is a load on the engine. After getting on plain good with an increase in RPMs, she will smooth out and run good at WOT. So I am still scratching my head on this. I did not get a chance to pull the boat up so I can work on the carbs in the yard under the shed. Hope to do that tomorrow.

Something interesting: I bought a Infrared Digital Thermometer and I decided to check the head temperatures after running out on the water. Had the following temp readings:

Top of heads - port & starboard, running about 110 degrees

Top of the cylinders - port & starboard running about 127 degrees

Side of cylinders at the Bypass Covers: #1 cyl 180 degrees, #3 cyl 170 degrees, #2 & #3 cyl about 160 degrees.

These temps at the block seem to be a bit high...... Has anyone taken temperatures in these areas?

Note, the water pumping out of the holes in the mid section is not steaming, there is really good water flow there and the water pump was replaced less than two years ago. I want to recheck these reading again tomorrow. Today it started raining on me and I did not have a note pad to write down all of the temperature numbers.

Thanks for reading, Tom

 

[Daviet]

Re: 1985 90Hp Evinrude running rough at mid range.

I would still check the spark under load and make sure you don't have an intermintent ignition problem.

 

[emdsapmgr]

Re: 1985 90Hp Evinrude running rough at mid range.

The thermostats open at 143 degrees. Usually the block should run about that temp. At idle it can warm up to 150-155 in summer warm waters. Once you get on plane and the pressure relief valves open in the stat housing, the temps can go down perhaps 20 degrees. I'd be concerned about 160 degree and higher readings. Keep in mind the overheat horn will come on at 212 degrees and silence at 175. So any reading in the 180 range is in the overheat category. Maybe your laser gun is off?

 

[NCmiller]

Re: 1985 90Hp Evinrude running rough at mid range.

Daviet, you gave me a good tip. I went down to the boat with my new inductive timing light and started the engine. I clipped on to the plug wires one at a time. Cylinder’s 1, 3 & 4 triggered the timing light, had a good light strobe on each wire. Cylinder 2, on the other, had would not trigger the timing light near the spark plug connector. Move the inductive clip about 3 inches away from the spark plug connector and the timing light would trigger. I thought this was interesting and I suspected a bad plug wire.

I went to the house and pulled an old plug wire off my blown 1979 115 and returned to the boat and installed it. The plug wire is not in good shape, the boot is split. After installing it, I started the engine and it was running much better. I took it out for a run in the river and it ran much better. We may be on to something! Got back to the dock and after tying up, I left the engine idling. After a few minutes it started missing again. I connected the timing light to cylinder 2 and the old plug wire was giving the same indication that the original plug wire gave me. I try to pick up a set of plug wires tomorrow at a local dealership. I hope they have a set for this older motor and my missing problem is taken care of after replacing the plug wires.

Will re-check the temperatures another day, the wind was blowing 10-15 knots and the river was a bit rough today.

Thank you, Tom

 

[Daviet]

Re: 1985 90Hp Evinrude running rough at mid range.

As a double check, swap the plug wire with another cylinder and see if the miss moves with the wire.

 

[NCmiller]

Re: 1985 90Hp Evinrude running rough at mid range.

Today I picked up a set of BRP 502365 plug wires. I assembled the wires and installed them on my motor. It started up and ran pretty good. I took it out and ran her. Motor ran great for a couple of miles. It idled good, mid range was good and high speed was good. Then I slowed down; motor started missing. Got back to the dock and put my timing light on the new plug wires. Plug wire in cyl 2 was not triggering the timing light near the spark plug boot just like the old wire did. So I though, may be it’s the plug… Moved the plug to cyl 1, symptom moved to cyl 1. Bad plug right? Got another spark plug and it too had similar symptoms. OK, back to square one. Checked compression, good, 135-140 PSI. Plugged spark plugs into wires and grounded them on the block, all plugs were firing strong. Installed plugs back to their original locations started it up and the missing was gone???? Go figure….. Took her out again, back to my original problem; missing at mid range. This is getting frustrating.

Knowing that the timing light would trigger a few inches away from the boot, I am now thinking that the inductive timing light, in some situations, may not trigger at all locations the plug wire.

OK, on to next plan of action… It appears that the ignition system is doing good, the next suspect area that I have not cracked into are the carbs. I think I will pull them off tomorrow and clean them good. I hope that take care of my problem.

 

[NCmiller]

Re: 1985 90Hp Evinrude running rough at mid range.

Made some progress today. I removed the carbs and cleaned them good. They were pretty clean and the only thing I noticed was the floats needed to be adjusted. Adjusted then and put everything back together. While installing the carbs I noticed that one bypass host between the carbs had a sharp bend in it and appeared to be kinked. So I replaced that hose.

Started it up and it ran great at the dock. Put it in gear and ran it with a load while tied up, still running great. Put the cover on and untied the boat. Got about 100 yards from the dock and it started missing. Like missing on one cylinder. Returned to the dock and with the inductive timing light I noticed the #1 plug had no fire. Pulled the starboard coils off, cleaned the grounds and swapped them. Still no fire on #1.

Got my Fluke DVM and ohm checked the charge coil, it was good. Moved to the starboard side trigger coils. Had an open between the White & Blue wire, not good, should be about 35 ohms. Checked between White & Green wire, it was good, read 33 ohms. Moved to the port side and ohmed it. Had 34 ohms between White & Blue wire and 34 ohms between White & Green. Port side is good.

After rechecking the starboard side I noticed the resistance was decreasing. At one time it was a high resistance, then it was 1k ohm then it was 500 ohms, then it was 60 ohms, then finally it was 35 ohms.

Now how interesting is that? Motor heats up with cover on, trigger coil goes bad. Motor cools down, trigger coil is good again. I think my problem has finally turned into a tangible problem that can be fixed. Went through a couple of cycles of running the motor to heat it up, checking the trigger coil checking the trigger coil and letting it cool down. It would be open and after cooling it was back into specs.

I have found a used trigger coil from and older motor that someone gave to my son. I checked its trigger coil and it checks good. It has 34 ohms on all coils. I pulled it off that motor late this evening and will be pulling the trigger coil off my 90Hp tomorrow morning. Will install this used trigger coil and hope that it works and my engine runs without missing. Hope to go boating tomorrow with confidence that she is running good.

 

[NCmiller]

Re: 1985 90Hp Evinrude running rough at mid range.

This morning I went down to my boat with the used trigger coil that I pulled off a parts motor. I checked my original trigger coil with my ohm meter and it was reading an open today. So it is a bad trigger coil. Got the flywheel off and replaced the trigger coil assemble with the used one that I have. Put everything back together and she started right up. Ran the engine at the dock for a while and she was running good. Pulled away from the dock got up on plan and no missing, it was running great. Run around in the river for a while and she ran great. It is nice to have it running good again.

Decided to take my daughter, grandson and wife out in the boat and run to Shackelford Banks, a good 15-20 minute run from the house; and sit on the beach, have a few cools ones, eat lunch and go play in the water with the grandson. Motor ran great, there and back. Boy life is good, motor is fixed, water was perfect and had lots of fun swimming with the grandson.

Thanks to all who read my posts and made recommendations that helped me get this engine repaired.

 

[Daviet]

Re: 1985 90Hp Evinrude running rough at mid range.

Glad you found your problem.
An electrical component starting to fail can be tough to find.