how to break in a rebuilt 60 hp Merc 2 stroke ?

[minnred]

Just had a total rebuild on my 1996 60hp Merc 2 stroke and altho the tech gave me a cheat sheet for breaking it in, I'd like to compare that with the experiences that others have had breaking their engines in.

 

[AVI_8]

Hi, I just downloaded the service manual for my 75hp 2 stroke, it mentions to premix fuel to 50/1 for the first 30 gallons so this is additional oil for the fuel before it goes to the engine and will get the 2 stroke added to the fuel.
Your engine may be different but mine has an 80/1 mixture at idle and theres a rod which is lifted by a cam which will increase mix ratio to 50/1 by wide open throttle so the above process of premixing will provide more lubrication while the moving parts, mainly pistons and rings bed in.

 

[minnred]

Hi, I just downloaded the service manual for my 75hp 2 stroke, it mentions to premix fuel to 50/1 for the first 30 gallons so this is additional oil for the fuel before it goes to the engine and will get the 2 stroke added to the fuel.
Your engine may be different but mine has an 80/1 mixture at idle and theres a rod which is lifted by a cam which will increase mix ratio to 50/1 by wide open throttle so the above process of premixing will provide more lubrication while the moving parts, mainly pistons and rings bed in.

The boat mechanic said I needed to run 25-1 mix for the first 10 hours.

 

[Dave1027]

You mix 2 stroke oil with the fuel in the fuel tank to 50/1. The motor's autoblend system will add in more oil which will make the actual oil ratio vary between 35/1 and 25/1

 

[BrianVT]

All above assume that your oil injection is working properly.

Break-in method opinions vary almost as much as which oil to use.
A quick search will have your head spinning wondering which method is "correct". ;-)

There's also a school of thought that extra oil prevents the rings from breaking in/seating properly.
Check out the mechanics that rebuild 2-stroke race bikes every week or two. Most of them say to do a couple warm-up/cool down (FULL cool down) cycles, with normal fuel and varying the rpms (below 1/2 throttle). Then run it like you stole it.
These guys are paid to maintain reliable, fast, race engines. I trust them and use that method on my bikes. I would do the same if I rebuilt my boat's engine.

Bottom line...don't stress over it. Anywhere from 25/1 (by you adding oil to the gas) or 50/1 (you not adding oil) will likely be fine. Go with what your mechanic says if he's giving you a warranty.

 

[minnred]

All above assume that your oil injection is working properly.

Break-in method opinions vary almost as much as which oil to use.
A quick search will have your head spinning wondering which method is "correct". ;-)

There's also a school of thought that extra oil prevents the rings from breaking in/seating properly.
Check out the mechanics that rebuild 2-stroke race bikes every week or two. Most of them say to do a couple warm-up/cool down (FULL cool down) cycles, with normal fuel and varying the rpms (below 1/2 throttle). Then run it like you stole it.
These guys are paid to maintain reliable, fast, race engines. I trust them and use that method on my bikes. I would do the same if I rebuilt my boat's engine.

Bottom line...don't stress over it. Anywhere from 25/1 (by you adding oil to the gas) or 50/1 (you not adding oil) will likely be fine. Go with what your mechanic says if he's giving you a warranty.

When the tech started rebuilding the motor, he strongly suggested to eliminate the auto oil injection system because he stated they are undependable, so now the only oil comes from the gas mix.

 

[jimmbo]

Mercury considers the first 10 hours as the Break-in Period. With older(pre Oil Mixing System) 24:1 was specified for the Break-in. Engines with Premixing Systems, 50:1 in the tank was specified for that period, just to Insure the Engine had some oil, if the PreMixing System wasn't working.

Mercury's procedure was the first 15 minutes at a Fast Idle in Gear, then varying rpms, but nothing over 3000 for the remainder of the first hour. 2nd Hour would be a Varying of Rpms between 2500 to 3400, not remaining at a particular Rpm for any length of time. As the time on the Engine grew, the Rpms could rise, and a minute or so(increasing as the hours go on) of WOT, and a return to 4000 rpm for a while. By the time 10hrs are on the engine, extended periods of WOT are fine.

 

[Dave1027]

When the tech started rebuilding the motor, he strongly suggested to eliminate the auto oil injection system because he stated they are undependable, so now the only oil comes from the gas mix.

I disagree with your tech on this point. The autoblend systems in Mercury motors are very reliable.

 

[jimmbo]

While the Mixing System on the V6s and later 3 and 4 cylinder Loopers is okay, the 'Autoblend' System brought out for the Older Inline Engines, should be removed from the Fuel Line, thrown as far possible from the Boat, preferably into a Fire Pit.

 

[minnred]

Mercury considers the first 10 hours as the Break-in Period. With older(pre Oil Mixing System) 24:1 was specified for the Break-in. Engines with Premixing Systems, 50:1 in the tank was specified for that period, just to Insure the Engine had some oil, if the PreMixing System wasn't working.

Mercury's procedure was the first 15 minutes at a Fast Idle in Gear, then varying rpms, but nothing over 3000 for the remainder of the first hour. 2nd Hour would be a Varying of Rpms between 2500 to 3400, not remaining at a particular Rpm for any length of time. As the time on the Engine grew, the Rpms could rise, and a minute or so(increasing as the hours go on) of WOT, and a return to 4000 rpm for a while. By the time 10hrs are on the engine, extended periods of WOT are fine.

Thanks for your input !

 

[minnred]

While the Mixing System on the V6s and later 3 and 4 cylinder Loopers is okay, the 'Autoblend' System brought out for the Older Inline Engines, should be removed from the Fuel Line, thrown as far possible from the Boat, preferably into a Fire Pit.

The motor is a 1996. But, the only thing that's 1996 anymore is the housing, everything else inside is brand new. It cost me $4700 to get it rebuilt.

 

[jimmbo]

Yours has the Tank where you add the Oil, under the Cowl?

 

[minnred]

Yours has the Tank where you add the Oil, under the Cowl?

It has a cap on top of the motor where oil used to be installed when it was oil injected.

 

[jimmbo]

It was never Oil Injected, just an Oil Mixing system that added Oil to the Fuel before it got to the Carbs. This system was pretty good.

 

[minnred]

It was never Oil Injected, just an Oil Mixing system that added Oil to the Fuel before it got to the Carbs. This system was pretty good.

Thanks for that info !

 

[racerone]

You paid $4700 to have this motor rebuilt ???------Way too much too spend in my opinion.----Your general location ?

 

[minnred]

You paid $4700 to have this motor rebuilt ???------Way too much too spend in my opinion.----Your general location ?

SW Washington state Was built by the shop that everyone referred me to. Great reputation.

 

[roscoe]

Be kind.

 

[minnred]

You paid $4700 to have this motor rebuilt ???------Way too much too spend in my opinion.----Your general location ?

The story:
I bought the boat last summer and the first trip out, was idling along when the motor went clunk, and stopped. Wouldn't turn over. Took it to the boat doc shop, and when they called me with the bad news, it was like getting punched in the gut They said that apparently, the over heating alarm had been disconnected, probably because the guy didn't want to hear the alarm. It was over heating because the impeller was bad and not supplying enough water to keep it cool. When I first started the motor, I saw the water peeing out like I thought it should, but apparently not good enough. When the motor was built, everything under the plastic was replaced with new. One part alone cost $2300. That's the story, of where all my future beer $$ are going for quite a spell BTW, the seller was moving at the time I bought it, and left no contact info .............

 

[jimmbo]

There are a lot of Unscrupulous People unloading things, after they wreck them.
I have weeded out a few, by saying I would want the Motor checked by a Shop, of my choice, and that I was willing to pay for that. Any seller who baulked at that idea, saw me leaving real quick.