Logo
FULL SITE MENU

1968 18 HP Evinrude low power output

T

tgregorybrooks

New member
"I am have what started as an

"I am have what started as an intermittent problem but has evolved into a continuous problem.

Several weekends ago while cruising along, the motor slowed down to about half power, like it suddenly was only running on one cylinder. After about 5 minutes, the power came back up to normal. I didn't really do anything to cause the power to drop or come back.

A couple of weekends ago, the motor started fine but never really got up to full power. I got to my destination and killed the motor to hang out in a cove. While in the cove, I pulled both spark plugs to see if maybe one cylinder was not firing. They both looked good to me. After about 3 hours of hanging out, I started the motor and it had full power again all the way home.

I have:
1. checked that fuel is coming out of the pump under pressure
2. replaced the points and condenser
3. check the compression 100 lower, and 95 upper
4. pulled the plug wires off one at a time while running the motor under load on the lake with no decernable difference in effect of the two cylinders.
5. rebuilt the carb
6. checked to make sure the choke is off (open) when running

The motor starts fine, it just runs now as if only at 1/2 throttle.

Sorry for the long winded description.

Any input is appreciated."
 
"Spark should jump a 1/4"

"Spark should jump a 1/4" gap on both cylinders on that engine with a strong blue lightning like flame.... a real SNAP! Does it?

Compression you state is okay but it could be better. Doubt that the problem is compression wise but keep a eye on it.

Use Champion J4C or J6C plugs gapped at .030 . The J6C may provide somewhat improved performance.

Let us know what you find.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:

http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store"
 
Joe:

I tracked down a spark

Joe:

I tracked down a spark tester from the auto parts store and had interesting results.

The lead for the bottom cylinder produced a consistent bold blue lightning bolt that jumped a 3/8" gap.

The lead for the upper cylinder did the same EXCEPT... during intermittent periods of cranking the engine (electric start) there would be no spark at all. Almost as if someone was pushing the kill switch off and on during the cranking of the engine.

I hope that makes sense.

Thanks
 
"Well, you definitely found th

"Well, you definitely found the problem. I'm sure Joe will have some useful input on this one."
 
"Remove the flywheel and check

"Remove the flywheel and check the armature plate for a bad wobble. If present, correct as follows.

(Magneto Armature Plate)
(J. Reeves)

If the armature plate has a a loose fitting, wobbling motion (the plate that the points, coils etc are attached to), it is usually caused by a slightly worn support ring. This allows the point setting to change erratically as the armature plate turns.

The cure is to remove the armature plate so that the support which is attached to the powerhead with 4 screws is visible. Then, with a screwdriver and hammer, or some tool of your choosing, and looking straight down at the support ring, make an indentation at what would be called the 12, 3, 6, and 9 O'clock positions. Install the armature plate and check for a smooth turning wobble free movement.

You may need to do that procedure a few times to obtain the proper fit (not too tight, not too loose), but it's worth the effort.

Use a small amount of anti corrosive grease between the aluminum ring and the brass support plate and also on the brass bushing of the armature plate when all is well.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:

http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store

Also, if the points are pitted, replace along with the condensers. Otherwise, clean and set as follows.

(Point Setting Of Magneto Models)
(J. Reeves)

Set the points as follows. Have the flywheel key aligned with the fiber rubber portion of the ignition points. Adjust the gap so that a .020 gauge will pass thru but a .022 will not. Should there be any question of the points being dirty (touching the contact with your finger would cause them to be dirty), clean them with a small brush and acetone or lacquer thinner.

NOTE: Should the operating cam have a small portion on it with the word "SET" imprinted, align this portion with the fiber rubbing portion instead of the flywheel key.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:

http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store"
 
"thanks Joe, it makes sense to

"thanks Joe, it makes sense to me. I did notice some wobble when I replaced the points and wondered if it was normal.

Looks like I have a little project for tomorrow evening. I'll let you know what happens."
 
"Neglected to mention..... if

"Neglected to mention..... if the top main bearing is slinging out oil bad, coating the points, then obviously that will need correcting."
 
"I did find that there was som

"I did find that there was some play in the stator plate which I fixed following the procedure above. Unfortunaltly, this did not correct the problem. I still have a good spark on the lower cylinder and good but intermittent spark on the upper cylinder. The top of the main bearing seemed fairly clean and oil free. Is it possible that this could be a coil issue?

Also, can you tell me what the hose does that goes from the top of the crankcase to the bottom of the engine? It's visible once the stator plate is removed.I replaced this awhile ago just because it was brittle and cracked but I do not really know what it does."
 
"one more question. If I do re

"one more question. If I do replace the coils, it makes sense to me to also replace the HT leads. Do I need to use specific sparkplug wire material or can I just use generic bulk plug wire from the auto parts store?"
 
"hey joe,

I see you've

"hey joe,

I see you've been out for awhile. I hope all is well with you. I am sure you are getting back to folks in the order that they posted but just in case, I wanted to let you know I still have a couple of outstanding questions.

thanks for your help"
 
"I beleave the hose drains exc

"I beleave the hose drains excessive oil mixture from the top berg to be recycled through the engine. You need to use solid core spark wire, not carbon fiber. Check at auto supply or lawnmower repair shop for plug wire. Should be able to buy it by the foot in bulk."
 
"Greg.... Before going into th

"Greg.... Before going into the project of changing plug wires, switch the coils. If the problem follows the coil, then obviously a new coil is needed.

I may be out for awhile longer. Had a back operation last Friday, encountering some problems due to same. Will try to check in from time to time."
 
The hose you refer to provide

The hose you refer to provides the lubrication to the top crankshaft bearing.

Fuel puddles at the bottom of the crankcase and it is pumped to the top bearing to lub it .
 
"u should have done a good tun

"u should have done a good tune up,while u were in there!...points/cond...if plate moves sd to sd much,another good option is,sierra magnatune ign modules...they wk fine...plate wobble,does not bother them.."
 
Back
Top