Breaking in rebuilt motor.

[mato0010]

Last year I rebuilt my 1976 35hp Johnson Seahorse. Afterwards I carefully followed the service manual for the proper break in procedures. Everything except for the oil mixture. My manual says to use 50:1 during break in but I was told to use 25:1 because it cant hurt. I put probably 3-4 hours running time on it and then stored it away for the winter.

Well this spring I decided to run another tank full of the 25:1 mixture just because I wanted to make sure it got enough run time for the break in period with the extra oil ratio. I didnt realize what I did until looking back but my first time out I spent a bit of time trolling. What ended up happening was that my motor had a hard time staying cool. Later on I dropped the lower unit and found a whole bunch of oily slimy crud surrounding the interior of the lower unit. My theory is that because I still have a high oil mixture, and because I didnt run the motor at high speeds, the oil didnt have a chance to burn off and resulted in that sludge coating.

I cleaned everything out. Removed my water pump, cleaned and reinstalled. The only thing Im still concerned about is if any of that sludge got up in the motor. Im also confused as to why this would cause my motor to have poor water/cooling circulation. Is there something more I should do before I put the lower unit back on and run it again? Should I ditch the 25:1 mixture and go to 50:1? If anyone could help explain to me whats happening I would appreciate it. Thanks in advance.

 

[Mark42]

Re: Breaking in rebuilt motor.

The sludge is unburned oil due to the hi oil ratio. So maybe the 50:1 is the right mix. Although I got the black sludge on both my newer Johnsons when going through the breakin using 25:1 . It went away after running regular 50:1 .

If its running hot, put in a new impeller and gaskets on the water pump, and a new thermostat. Switch to 50:1 or 40:1 and run it for a while and it should clean up.

 

[mato0010]

Re: Breaking in rebuilt motor.

I put a new water pump kit in when I rebuilt the motor late last summer. I also put a new thermostat and gasket in. When I dropped the lower unit and took apart the water pump last week, everything looked in good condition, just a whole bunch of that sludge. The impeller and housing looked practically new.....as it should.

So would there be any way that the sludge could be getting into the engine and causing bad water circulation? What other reason would I have for it not cooling properly?

 

[wilde1j]

Re: Breaking in rebuilt motor.

Breakin for any new/rebuilt motor should use double oil for the first ten hours and the running rpm should be varied. After the first few hours very short periods of WOT are typically called for. If you've done nothing but baby the motor, it's not likely the rings have been well seated and the sludge you found is likely due to running at very low RPM's. The sludge isa just letting you know how you've run the motor. I've broken in a bunch of new/rebuilt motors and never had the sludge deal. Once you're beyond the breakin period (usually ten hours), that's the time to use only 50:1 mix.

 

[mato0010]

Re: Breaking in rebuilt motor.

I took it all apart, cleaned all the oil sludge from the lower unti, put back together and cooling system works great but problem still persists.

I took it on the lake last weekend and when I put it in gear Im only able to get about 25% power out of it, like its being bogged down. A couple years ago I had the same problem so I took it in and they said it was the base gasket. They replaced it and it worked great. So could the base gasket go bad after 2 years? I do store it outside and live in the midwest. How can I test it to see if it is in fact the base gasket? Im assuming the base gasket replacement would require me to pull the powerhead completely out and the gasket sits between the powerhead and the lower unit.

 

[AEROCOOK]

Re: Breaking in rebuilt motor.

Just curious, how do you know it was running too hot? Is there an overheat alarm?
As for the low power issue, if you had any of that 25/1 mixture fuel left in the carb during storage, I'll bet the carb needs to be cleaned.

 

[mato0010]

Re: Breaking in rebuilt motor.

When I put my hand on the head I can tell whether or now the cooling system is keeping the motor cool enough. Typically I can leave me hand on it but I know its not working well when it gets too hot to touch. I didnt have a problem with this my last time out.

As for the carb, thats a good point. I will take apart the carb and do a thorough cleaning. You think the extra oil partially clogged up the jets?