What to do about break in ?

[JJB]

I Have a fresh rebuilt 175 Johnson and wont be able to use it for a few months . I found water in my transom and will be working on the boat for a while . I now have the engine on a stand . Would it hurt it to idle for 5 mins every few days to keep things moving until I can get it broken in . I have heard thats it's bad to run it a low rpm's for to long when breaking in a OB . and not to use ears for to long . I using evinrude/ Johnson Hd 50 blend oil , Is that ok for break in period ? Thank's JJB

 

[iwombat]

Re: What to do about break in ?

You're better off not running it and leaving all the assembly lube in place until you're ready to really use it. A little fogging oil in the top end wouldn't hurt though.

 

[JJB]

Re: What to do about break in ?

I have already ran it for 10 mins to check it out , sound good . There is oil / gas in the carbs that could be a problem I think . So it be better to drain the carbs and fogging the engine ? Thanks JJB

 

[Cricket Too]

Re: What to do about break in ?

Yeah you might want to just run it one more time and fog it, running every couple of days won't do it any good, just fog it good so it's protected. Don't run the fuel out of the carbs, but you can manually drain them if possible. Running the fuel out isn't a good idea, especially on a rebuild, as it will cause one or more of the cylinders to run with no lubrication, and you don't want that, especially on a rebuild.

When you do start running it for the break in period, run it at a 25:1 ratio for a while, first 10 hours or so.

 

[iwombat]

Re: What to do about break in ?

What Cricket said. And, if you can't drain the carbs, just put some fuel stabilizer in the gas tank (and that 25:1 mix) and run it long enough to make sure you pull a bowl full of stabilized fuel into the carb. Then, fog away.

 

[Dhadley]

Re: What to do about break in ?

Don't be afraid to run it on the hose for as long as you like. As long as it's getting water you can run it for 5 minutes or 5 hours. In fact when starting a rebuilt motor we like to let them idle for an extended period. The motor will warm up, the T-stats will open, the motor cools down and the cycle starts all over. Those heat cycles really help the rings seat.

If it's going to sit in storage the stabilize the fuel as mentioned and have at it this spring. Shouldn't be a problem.

 

[Scaaty]

Re: What to do about break in ?

" getting water you can run it for 5 minutes or 5 hours. In fact when starting a rebuilt motor we like to let them idle for an extended period. The motor will warm up, the T-stats will open, the motor cools down and the cycle starts all over. Those heat cycles really help the rings seat. "
Been a LONG time since I had anything new, or even rebuilt (good preventive maintenance keeps it that way), but I will soon have back together a Merc Tower of Power, new rings, seals, piston overbore, etc, and I was thinking along the same lines. Not a lot of load this way of course, but lots of driveway warm-ups, some open water running, speed up the time of break-in..

DH, what do you suggest as number of hours for a ring break-in?

 

[Dhadley]

Re: What to do about break in ?

The break in depends on how it was machined. To what tolerance and to what finish. Some folks like to bore to the tight side, some in the middle, some to the loose side. There are an almost unlimited number of finishes you can go to also.

It also depends on set up. If the motor is on something that won't allow a good top rpm, then you'll want to bore to the loose side. If the end user is going to insist on something other than 87 octane (we're assuming this motor is stock, as produced) then you'll want to be a little loose too.

We built motors in a lot of ways to see what effect it all has. I really like to bore to the middle of the spec and use the plateau hone finish.

On any of my motors I idle them for 2 to 4 hours before begining the break in on the water. It doesn't matter if it idles for 1/2 hr at a time or 4 hours straight. The heat cycle is what you're after. Above an idle (in neutral) and you're putting more water thru the block and it'll stay cooler so you don't get an effective heat cycle.

And while it's idleing you don't need double oil. 50:1 is more than needed at idle.

Which 175 do you have? What did the machinist bore it to? Or what did he use for a standard bore size?