Breaking in a rebuild....

[Esox_Magnum]

Having my 91 115 Merc rebuilt, scored #1 piston unfortunatly means a bore job and new pistons... What will be the best way to make sure I get the best performance and longevity out of it once I get it back?

[Sonicrunch]

Do NOT work the motor hard for first hour.

Keep it 1000 RPM under max RPM for the first hour.

Vary the RPM during this time too.

After that, always warm her up and use good oil.

[marine_man]

I believe you normally double up on the oil for about 10 gallons as well..

marine_man

[Esox_Magnum]

I believe you normally double up on the oil for about 10 gallons as well..

marine_man

No idea on the mix ratio for this motor, would I be safe with a quart per 16 gal or do I need more or less oil?

[boatfixer]

First thing I thought of right away is, what does the mechanic rebuilding the engine want you to do? He's the one standing behind his work.

In regards to the ratio, isn't your engine oil injected? Keep that in mind when pre-mixing for the break in period.

[Loon]

Definitely vary the RPMs for the first 2 hours between idle and 3/4 throttle.

Don't stay at any RPM for more than 5 seconds...keep it moving either up or down.

No extended idle...keep it moving.

Crack it open for 1 minute every 10 minutes during those first 2 hours.

Definitely double up the oil during those first 2 hours.

[marine_man]

First thing I thought of right away is, what does the mechanic rebuilding the engine want you to do? He's the one standing behind his work.

Bruce is right on here.. check with the guy who rebuilt it first.

Since your motor is oil injected, a double mix (which in this case would be just using a 50:1 ratio since the oil is already injected) would be a pint to 6 gallons.

marine_man

[Esox_Magnum]

No worries I'll ask him when I pick it up what he recomends, I know he does some sort of break in at the shop...Yes I'm injected and plan on running a tank of pre mix through it also, tanks a 16 gal....Almost 25 years of owning boats, only the 2nd time I have ever had one to a mechanic...