71' Johnson compression test...

[Colwell87]

Hey Guys,

I have a 71' 60HP Johnson that I've been messing around with and trying to get running. I've got good spark at this point but was curious about the compression.

Cylinders 2 and 3(from top to bottom) have about 105 pounds consistently, cylinder 1 has about 85-90 pounds. I've been trying to figure out what is a good amount of compression and the findings are all over the place, some people say they have about 150 per cylinder in a Johnson of similar HP, others say about 115. Also, with the rule of thumb being that as long as each cylinder is within 15% of the others, its fine, it would be safe to say I'm cutting it kind of close.

Are there any options to help compression? I've heard some people talk about squirting Mystery Oil, or something like that, directly in the cylinders? I've added seafoam to my gas and ran the motor for about 20 minutes in the river, it starts perfectly, shifts(R-N-D) fairly smooth, but only moves along at about 8-10mph.

When I pull the spark plug cables when the motor is running, you cant notice much, if any change when pulling plug 1 and 3, quite a bit of change when you pull plug 2, but the motor doesn't die -- this leads me to thing I'm getting some amount of power from 1 or 3.

Would dirty carbs provide a lack of fuel to the cylinders and cause them to run poorly?

I've had a lot of help from the forum with my water pump and getting spark to the motor, so any information is appreciated!

 

[Joe Reeves]

Re: 71' Johnson compression test...

Those older 3 cylinder models have been known to have compression that approaches 135/150 psi easily but then others drop down some.

The bad point of your engine is that there is a 20 psi difference between the highest and lowest reading (85/105) which is not good. However, that may simply be due to a dry cylinder. Using a old spray bottle, shoot some premix in the cylinders to lube the cylinder walls, crank the engine over a few times, then take another reading.

Reading further down in your notes, I see that you have the engine running so obviously the cylinder walls should be lubricated UNLESS as you suspect.... carburetor trouble. A fouled carburetor or carburetors would cause a engine to run lean which could cause the cylinder walls to score.

However, clean the carburetors and make sure that you manually clean the high speed jets that are located horizontally in the center bottom of the float chambers, way in back of the drain screw bolts. Use a piece of single strand wire as solvent just doesn't do that job properly.

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note 1: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

Note 2: If the engine should be a three (3) cylinder engine with three (3) carburetors, start the adjustment sequence with the center carburetor.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

 

[orbanp]

Re: 71' Johnson compression test...

Some time ago I asked the same question about the compression in a 60ESL70B motor, here are the answers: http://forums.iboats.com/johnson-evinrude-outboards/60esl70-compression-531872.html
So I guess your engine is serviceable. The reading also may vary depending on the gauge used.
You mentioned that you have spark. As your engine has battery CDI ignition, you should get about 7/16" in free air. Do you get that at all three cylinders?
How do the plugs in #1 and #3 compare to #2 after a run? How does the plug color look like? That could give some indication how the engine and individual cylinders work.
Try changing plugs, sometimes bad plugs could give lower performance.
Also, do you have the correct plug? It is Champion L76V Surface Gap or QL77JC4 gapped at 0.030".
If any of your carbs are running lean (the plug in that cylinder would be really white), you should fix that as the cylinder will overheat and it will destroy it in short order.


Good luck, Peter

 

[phillnjack2]

Re: 71' Johnson compression test...

i do like this joe reeves answers
they are always so clear and just make it all seem so simple.

there is some people who give the same advice obviously,but never this clear and concise.
very hard not to follow this stuff to the letter.

great advice and im sure will help this fella a lot.
im liking reading it, as i have a 3 cylinder and most of this also seems to cover my engine as well.

i neverthough about doing the centre carb first, but it makes perfect sense now.


phill