1973 Evinrude 6HP running super slow

My 1973 Evinrude 6HP starts up just fine and runs consistently for long periods of time but it runs super slow - maybe 1/4 of the normal speed - that's the only symptom. Ive thoroughly cleaned the carb and that didn't help. Im going to give you the full backstory and see if anyone can help:

-Im not sure if this is related to the issue but its been underwater several times in the last year and a half. We had some historic floods in Texas and my garage flooded 3 times this year. Each time, I pickled the engine, let it sit for a week and got it running. It actually ran even better after the first pickling....so im not sure if this has anything to do with the current issue, but wanted to add this info in case it helps.

-After cleaning the carb didnt work, I went and bought a cheap compression tester from harbor freight and both cylinders are only reading 15psi but its hard to believe that they could be that low. would it even run on 15psi?

-When I took the spark plugs out I noticed that the bottom plug was fairly clean and dry, the second, however, was dripping water/oil.

What should I do next to try and fix? My knowledge of fixing outboards doesn't go much further than the sparks and carb.

Many thanks!

I opened up the cylinder case and this is what it looks like. Looks pretty clean to me... Though you can see that the top cylinder has a lot more moisture/fuel-oil in the chamber than the lower one

here...the files didnt upload the first time

Anyone have thoughts?

Many thanks. I ended up replacing the plugs and then took off the fly wheel and cleaned and reset the points to .020
I also cleaned up the coils and the wire contact points. It seems to be running much better now but its hard to tell until I get it in the water and push the boat with it. If its still not running well, ill replace the coils and condensers and go from there. Strangely, the compression tester is still reading 15psi..... so I must either still have a problem or this cheap compression tester from harbor freight isnt worth its weight in coal.

Good idea to test it on a lawn mower. I'll do that tomorrow. Yes, im pulling the rope 4-6 times until the tester levels out on PSI. I did take the head gasket off and clean it up along with the sides that contact with it...I admit, it didnt look super fresh so yeah, I imagine that you are right - I should just replace. I'll also take your advice and surface the head. I was going to wait on replacing the coils as they dont look cracked and will be around $50 for the pair but I suppose a spark gap test will let me know if they are needing replacement?

When im ordering these parts, in your opinion, is it worth it to spend the extra money on the OEM parts or are aftermarket parts like Sierra about as good?

I did the cylinder drop test and it ran on both cylinders - though I did notice a drop in power while running on only one. I also got an ignition spark tester as you recommended and it will jump a gap of just over 1/4" on both wires though at that distance I noticed that every 2nd or 3rd pull, it skips the spark...so not sure if that indicates that its weak. So seems like my biggest issue is the low compression potentially due to a leaky head gasket/warped head. Im going to go ahead and order a new gasket and ill surface the head as you recommended. I tested the compression tester on my riding lawnmower and it read about 75psi - though on my push mower it only read 15psi (the mower runs great). given that info, would you accept that as qualifying the tester as working as it should?

Also, on the riding mower the compression tester will hold the psi reading pretty steadily whereas on my evinrude, the reading starts dropping pretty quickly after I stop pulling...sounds like thats probably the smoking gun indication that im leaking air from the cylinders, right?

I ordered the head gasket but, in the meantime I resurfaced the head and cleaned the current gasket. I also brought the compression gauge back and swapped with a new one. Now im reading 75psi in both cylinders. You mentioned that it should be around 70. Is that good for a motor like this one? Ive always head that it should be over 100 but im not sure if thats a reasonable expectation on a motor of this size. What do you think?

Well, I had totally forgotten about this thread. Hadn't run this motor since 2015, cranked it up, ran great in a bucket but when I put it on a boat, it pushed the little 12ft super slow. Went online to check it out and voila, I see this thread from 3 years ago and just remembered that I never figured out how to fix this problem. Given that it doesn't seem to be a compression or spark issue, what would you recommend doing? Replace the coils? Anything else I can do?

Did you surface the head and install a new head gasket?

kimcrwbr1 said:

Did you surface the head and install a new head gasket?

Click to expand...

Yes, I did. It doesn't seem like thats the problem. Getting 75psi in each cylinder.

Since I still don't know what the problem is, my plan is to order and replace:

Ignition coils
Consensers
Head gasket (again)
Impeller (its probably old)

Given that I've got 75psi in each cylinder, reset the points gap, have good spark, did a cylinder drop test and still don't know what the problem is do you have any other suggestions? Anything on the list of things to replace sound unnecessary based on the information given?

Install a new fuel pump diaphragm at about $4.00----Pull flywheel of to inspect the coils.----Many of those motors have 2 new ones already !----Does spark jump a gap of 1/4" or more , yes or no ?

If you did not manually clean the brass high speed jet that's located in the bottom center portion of the float chamber with a piece of single strand steel wire.... do so now as carburetor cleaning solvent just doesn't do that job properly, and the engine has been just "sitting"...... again!

Check that the throttle butterfly is opening all the way (horizontal) at full throttle.

Check that the timer base under the flywheel isn't sticking.

Well, I decided to start again with the fuel pump. I inspected it a couple years ago and don't remember seeing any issues. This time, however, I tore the whole thing apart and purchased a repair kit. While I was cleaning the valve housing in the pump, I noticed some gunk in the corners of the two deep indents. As I was cleaning that out, I noticed that there is a small hole in each of those depressions that was clearly clogged by the sediment. Im not sure what the exact purpose of these tiny holes are but I assume that if they are clogged, the fuel isn't going to circulate properly in the pump...so I'm hoping that this was the issue. I haven't gotten a chance to take it out yet but have my fingers crossed.

And how did the story end?

This post if about a year old. That indicates that the engine is either running fine or has been converted to a anchor. Let it die.

I assume you have a engine problem yourself.... Best to start a new post under your own title and screen name to obtain full coverage rather then to be buried under another members post.