Got a few question on a 71 25 johnson

[JustJiggin]

Ok I got this headache of a motor a while back and it ran fine for a few weeks. Then everything that could go wrong has went wrong. First it started with the clutch dog going out had to rebuild all the gears in the lower unit. Then it started burning plugs, and running like crap. So that lead to it not wanting to crank so I pulled on the pull rope some many times it finally broke. Well I replaced that. As well as the plugs and cleaned carb. Ran great after fixing those problems idle and top speed great. Next the water pump stopped working, which lead to it running hot. Last but not least I had a bad leak around the o ring where the shift rod goes. So needless to say the lower unit filled up with water without me knowing. I must have ran it about a week and a half without me knowing the lower unit was full of water instead of gear oil that I had just changed. So I pulled the skeg off to check the damage. To my surprised very little to any damage. I lucked out on that! Did happen to have a shear pin broke in 2 places but prop still spun the shaft some how. I guess what saved my gears was the grease I put in the bushings when I replaced the gears. It didn't wash away as fast as the gear oil. Anyway that's what all I've ran into with this motor.

Other than replacing the plugs every 2 or 3 weeks. I never found out why it was burning a plug. I read about a bad thermostat but I checked mine and there wasn't one in there where it's supposed to be. When I do put the new plugs in it runs almost near perfect. I'm running a pint of oil to about 4 1/2 gallons of fuel. But would like to solve the problem on the plugs. I heard these motors were bad about burning plugs.

I'm also trying to figure out how come my motor just all of a sudden started running hot. My motor was running at the right temp then all of a sudden it decides to run hot what's the deal? I really don't think I ran it hot long enough to do any internal damage. The day I discovered it was running hot I looked at the exhaust hole no water coming out. So I Immediately shut it off and waited a little while for it to cool down. I started the motor back up and it was peeing out the exhaust. I thought that's strange. I started back to the ramp and it stopped peeing. Then it would start back peeing. It would pee and something and still seems hot. I got it back to house and took the lower unit off to check the water pump as far as I know everything it clear. That's when I found the water in the lower unit instead of gear oil. There was not a gasket on the bottom of the impeller plate or on top of the impeller plate and the housing. Should there be one there? Also one of the impeller blades has only about 75% of it's blade. In other words one of the blades it chipped off a little. The copper tube that that goes up into the exhaust housing which leads to the power head. That little rubber grommet that the copper tube goes in is missing there was tape around the tube instead. I'm replacing all lower unit seals and gaskets this week as well as a new impeller and see if that fixes the over heating problem. If replacing everything doesn't work I have no other ideas why it could run hot. Other than the thermostat and its not in the motor so it's not stopped up.

As far it running like crap I'm not sure. Here is what it was doing. I went from running like a brand new motor to real sluggish like it wouldn't reach full throttle. It would take a little longer to plane off but eventually it would plane off but not reach top speed. Then after a few days it wouldn't even plane off or reach top speed. It would idle fine but would when I went to take off it wouldn't hardly go. I checked plugs and fire one plug had a little grey on it. The link and stop that is connected on the Armature plate was loose. So I might not have been getting full throttle. Since the Link and stop was almost falling off it wasn't rotating around to engage the cam follower which engages the throttle on the carburetor. I'm getting good fire it seems I checked the fire with the plugs out. May go ahead and replace the points and condensers just to be safe. I don't think it's fuel related as I replaced all of the fuel lines and hoses and cleaned carb. So I am not getting any air leaks of fuel leaks anywhere. Only thing I think could be a fuel problem would be the low speed jet I did turn it out of whack when putting the carb back on I think. Also what about the high speed jet. Do these motors have one and if so where is it located. Has far as I know I haven't turned it by accident?

Sorry for such a long post but I had to explain the problems I'm having with the motor fully so maybe someone can pick up on what's causing these problems. Thanks for the ones that take the time out to read it and maybe add the insight on what could be causing several of these issues.

 

[jb93]

Re: Got a few question on a 71 25 johnson

If it were me, I would back up and start from the beginning and address ALL the critical items.

1. Cold compression check report values. If they are much less than 90 psi or not within 10% of each other, then cheaper to find you a used powerhead with good compression and go from there instead of rebuilding.

2. Open air spark check...not just holding plug against block and seeing if you see spark. It must jump an open air gap of 3/8-7/16". Spark tester is about $7 at auto parts store if you don't have one. Go ahead and put in new points and condensers...even if you have good spark it's cheap insurance. Less than $20 here on iboats. Ignition Tune Up Kit for Johnson/Evinrude 172523, GLM 72820 - Sierra - iboats
If your coils are cracked and you have spark, go ahead and replace anyway. They will just fail anyway...or be unreliable once hot.
Ignition Coil for Johnson/Evinrude 582995 584477, Mercury/Mariner 802371A1, GLM 72100 - Sierra - iboats
You can probably just cut 1/4" off end of your plug wires and reuse them, but if they are original and sheathing is cracked, etc. then just replace. 7mm copper core wire. Dealer, Tractor Supply or maybe auto parts store...NAPA seems to be best about having marine stuff.
3. Clean carb...know you said you did but cleaning means disassemble, soak, clean out all passages, etc. then put on new carb kit parts. Again cheap here on iboats. Carburetor Kit with Float for Johnson/Evinrude 398729 396701 392061, GLM 40560 - Sierra - iboats

3. Check fuel system...replace all hoses if original as they won't be ethanol compatible. If you don't they will likely end up fouing up your clean carburetor. Check fuel pump, replace as needed.

4. You obviously need to reseal the lower unit and put in new impeller. Here is both the seal and impeller kit w/o housing assuming yours is fine. Do a pressure/vacuum test once completed. If you don't have tools for it, probably get it checked at local outboard shop for small charge.
Water Pump Repair Kit for Johnson/Evinrude 382468 - Sierra - iboats
Lower Unit Gear Housing Seal Kit for Johnson/Evinrude, GLM 87606 - Sierra - iboats

Once you have good compression, reliable spark, fully cleaned fuel delivery system and a resealed lower unit you have pressure and/or vacuum tested...then you can go on to setting low and hi speed carb adjustments and do the link and sync.

All of the above won't cost you more than about $100-150 in parts and about 2 days of your time. Then you will know that you have addressed everything top to bottom instead of just cobbling it together when things go wrong. There are tons of threads on here about procedures and how to set carb adjustments, etc. Check the sticky at the top of the Evinrude/Johnson forum...lot of good posts in there for reference.

Oh...and you must invest in an OEM Service Manual. Ken Cook has original factory manuals reprinted. Yours is cheap...$36. You might find a used copy on Ebay cheaper. 25R71 Marine Literature

 

[bbstacker1]

Re: Got a few question on a 71 25 johnson

Unless you already have, I think it would be wise to try and locate that missing piece of impeller, if that is stuck someplace in the powerhead that very well could be your reason for overheating. And of course you are going to replace that tape with the missing grommet and put in a thermostat.

 

[F_R]

Re: Got a few question on a 71 25 johnson

Agreed, find that impeller chunk.

There is a plastic water restrictor in the exhaust housing, right under the powerhead. When the motor overheats, it melts that restrictor.

And on to the long list of woes, I guess you replaced the tape with a real grommet, right?

And I'd say you have an ignition problem. It is not running on both cylinders all the time. When it drops one, it will run but no power. You have to pull the flywheel and check out the whole system.

And you are using too much oil. OK, if that makes you feel good go ahead. But don't complain about fouled plugs. Besides, the ignition problem may be causing that. Correct mix is 50:1, one pint of oil to 6 gallons of gas.

Yes, there is a fixed high speed jet, called an orifice plug, in the very bottom of the carburetor float bowl, deep in the hole behind the hex plug. It takes a special screwdriver to get it out without damage.

Overheating may have caused the head gasket and/or exhaust cover gaskets to leak. That lets water into the cylinder, which also may have something to do with your fouled plugs and lousy running.

So......what have I missed?

 

[JustJiggin]

Re: Got a few question on a 71 25 johnson

Your talking about the exhaust side cover gasket correct F_R?

 

[F_R]

Re: Got a few question on a 71 25 johnson

Correct. You have to pull the powerhead to access that plastic restrictor anyway.