1958 Evinrude 10hp compression problem

[MuleyQuest]

I am trying to get this motor going again after sitting in storage for last 35 yrs. I replaced the coils, set the points gap, replaced a bad plug wire, cleaned the carb, replaced the impeller, changed lower unit oil. All the normal stuff. I still can't get it to idle and run at low speeds. My compression is 60lbs on both cylinders. I have not tryed any decarb yet since I have not been able to run other than in a garbage can of water so far. Is this way to low for compression? I thought it should at least run fair since both cylinders matched on compression. Maybe this should be turned into a boat anchor? I hope it is not a lost cause. By the way, I am new to this forum and looking forward to being a part of it. Thanks in advance for your help.

MuleyQuest.

 

[F_R]

Re: 1958 Evinrude 10hp compression problem

That is too low. Too bad you did all that work already. You might as well go the rest of the way and fix it. But before you do, check the wrist pin bearings. Those motors were bad about beating the pins loose in the pistons. Remove the plugs, stick a screwdriver in one of the holes, and follow the piston as you slowly rotate the flywheel by hand (follow, don't push). As the piston reaches about half way on the downstroke, stop turning. Then give a push on the screwdriver. If you get a clunk, that is the wrist pin. You may be able to find some good used ones, but to fix it right with the newer, updated parts involves replacing the pistons, rods, and wrist pins. Once updated, they are a tough motor.

They were also bad about wearing out the non-replaceable pinion bearings in the lower unit if you run it full of water. Have you checked into that?

 

[MuleyQuest]

Re: 1958 Evinrude 10hp compression problem

I have not checked the pinion bearing. I was unaware of this problem. I will check into that as well. Thanks for the quick response. I am just hoping I will be able to get it to idle after a little more tinkering. I am new to outboards but have been able to get so much info in a short amount of time from this forum. Thanks again for your help. I have another 1970 25hp Evinrude that looks like it might be worth putting rings in. Lower cylinder has low compression. But that is a post for another day.

Muley Quest

 

[samo_ott]

Re: 1958 Evinrude 10hp compression problem

60#'s is low. You can try a decarb but the engine has to be running to do that. You could just spray some deep creep in the cylinders and let it sit and see if that helps to loosen the rings up.

 

[JB]

Re: 1958 Evinrude 10hp compression problem

Well, I disagree.

This is a rope start outboard that hasn't run in a generation. I would accept 60# compression, particularly because the cylinders are near equal.

Go back into the carb. Find the smallest of the three tiny orifices into the throat and clear it. You may need to remove the Welch plug opposite it in the top of the carb. There is a replacement for the plug in the overhaul kit. I usually can clear it with a single strand of copper wire bent into an "L" and run in from the base, but a very small drill bit works well.

Another possibility is insufficient advance in mag timing at idle.

Are you using an OEM Service Manual to work on this engine?

 

[MuleyQuest]

Re: 1958 Evinrude 10hp compression problem

Thanks for the info. I will check the carb again. I still need to check for slack in my pistons as well. It does sound like a timing issue when it is running rev'd up. I think I hear an occasional ignition popping noise like a small backfire. I didn't think I had adjustable mag timing on this engine. I don't have a manual yet and have so far been just figuring it out as I go. I did move the brass cam plate out that links up to the roller on the throttle and the problem got worse. I moved it back in as far as I could and problem was better but still very bad. I need to find some more time to get back to work on this thing. Thanks again for all your input.

MuleyQuest

 

[jbjennings]

Re: 1958 Evinrude 10hp compression problem

Muley, here's my opinion for what it's worth:

If your motor actually has only #60 psi then it's a total piece of worn out junk that you shouldn't even bother with. However, in the several 50's 10hp outboards I've worked on, I've not seen one with 60#'s in both cylinders. I've seen one with 60#'s on one cylinder and 80 #'s on the other. The 60psi cylinder had a bad wrist pin and scored cylinders. It's more likely that your gauge is off 15 or 20 psi in my opinion. I'll bet if you can get the motor running good if you get it fixed right. Check the gears on the tiller and armature control gears to see that they are meshed right. Check and see that the throttle plate in the back of the carb Barely begins to open when the throttle cam roller passes the two marks on the throttle cam on the armature plate. Also, make sure the little lever that the cam roller sits on is nice and straight and not bent, making it impossible to synchronize the throttle to the magneto. You might also check that your flywheel key has not sheared, allowing the points cam to get out of time. Just some things to check...... I'd find an outboard with known compression to check and see how much your gauge is off. If it only has 60psi, it'll never idle smooth no matter what you do.
JBJ

 

[MuleyQuest]

Re: 1958 Evinrude 10hp compression problem

I finally got this motor to run good. I checked everything that was suggested and appreciate it very much. My pistons don't have any slack by checking with the screwdriver in the spark plug hole and I have verified my compression gauge to be accurate. This motor truly does have only 60 psi compression. The spark plug wire I replaced was with carbon fiber core. This was my biggest problem. I replaced them both with metal core wire and now the motor idles and runs very well. It will now start on the very first rope pull. Now that I can run it, I will attempt to perform decarboning and see if it helps my compression. At least this motor is now usable for awhile longer.

MuleyQuest