Rebuilt Break-in

[stockypower]

I just installed new rings and had cylinders honed out on a 1983 Johnson 175hp engine - blew a ring on one cylinder last season. I'm looking to put it into the water tomorrow and am looking for tips on a break-in period. All bearings were in good shape, re-used and place back the same way they came out (poor-man's rebuild). I fired the engine up and it sounds pretty good. thx

 

[DJ]

Re: Rebuilt Break-in

stocky,<br /><br />Run a 25:1 oil to fuel ratio (one quart to six gallons, 87 octane) for at least 12 gallons.<br /><br />Nothing but idle the first hour. Very short bursts up to 3000 rpm, the second hour.<br /><br />From then on, up to ten hours, avoid WOT and vary speed often.

 

[stockypower]

Re: Rebuilt Break-in

Thanks djohns - I thought that a higher octane rating would be better and I believe that is what they have down at the marina. Maybe I'll fill it up before I drop it in. Why the low octane? Will the 25:1 help break in the new rings?

 

[DJ]

Re: Rebuilt Break-in

stocky,<br /><br />Higher octane fuels tend to create deposits because they burn slower.<br /><br />The 25:1 will help seat everything and provide lubricant to wash away microscopic shavings, etc.

 

[chilifriedpork]

Re: Rebuilt Break-in

No need to go above 87 octane, unless it's a racing high perf. engine with a high compression ratio. Remember, octane retards the explosion. A difference will be minimal between octane, and in the end a waste of $$. (if your engine knocks under load then possibly raise octane)<br /><br />Some people say running 25:1 premix is bad, because in fact it is running the engine leaner (less gas because of more oil) Rich and lean is a fuel to air ratio.(if I'm not mistaken)<br />-Though, I would run a pre mix with a bit more oil in a break in period because of the increased friction. (the parts have to bed in)<br /><br />The main thing is take it easy, don't go at WOT. Remember it's not like a car where the engine is barely working to move itself on a level surface, with a boat it is like constantly going up a hill.<br /><br />Keep it in mind and good luck