How to break in rebuilt big block mercruisers/

[tmh]

I bought a 1988 Cruiser with twin Mercruiser 454s that were totally rebuilt 3 years ago. Rebuilt block and all new trimmings like carbs, starters, hoses, ignition, etc. The boat sat while various attempts to refurb it were done, in addion to the engine rebuilds. The engines were installed last year and ran long enough to say "they run" then winterized. I bought it this year and ran them for only a min. or two to make sure they ran.

I assume the oil in there now is from just after the rebuild 3 years ago. I have no way to know what oil was used or anything about it. So now I will be putting it into service in a month or so and have a few engine questons:

1. Do I treat rebuilt engines like new for break-in period?

2. Is there a different oil or additive for break in period?

3. I think I'll change the oil before putting into service as I want to know what's in there NOW. When do I change it again? 10-15 hours or just wait until next season like most marine engines used 3-4 months per year?

4. 6 qts. for a 454 big block right? My oil pump is a 5 qt. capacity.... darn.

Thanks.

 

[rbh]

Re: How to break in rebuilt big block mercruisers/

I would it would be guess it would be a good thing to change your oil when you have a few hours on it. check the filter (open it up extend the paper) and check for metal chunks. there is probably going to be some fine particles from the machineing but nothing large hopefully?
rob

 

[mkast]

Re: How to break in rebuilt big block mercruisers/

1. Do I treat rebuilt engines like new for break-in period?

2. Is there a different oil or additive for break in period?

3. I think I'll change the oil before putting into service as I want to know what's in there NOW. When do I change it again? 10-15 hours or just wait until next season like most marine engines used 3-4 months per year?

4. 6 qts. for a 454 big block right? My oil pump is a 5 qt. capacity.... darn.

Thanks.

Follow the Mercruiser maintenance manual.
What is a five quart pump?

 

[wca_tim]

Re: How to break in rebuilt big block mercruisers/

I bought a 1988 Cruiser with twin Mercruiser 454s that were totally rebuilt 3 years ago. Rebuilt block and all new trimmings like carbs, starters, hoses, ignition, etc. The boat sat while various attempts to refurb it were done, in addion to the engine rebuilds. The engines were installed last year and ran long enough to say "they run" then winterized. I bought it this year and ran them for only a min. or two to make sure they ran.

I assume the oil in there now is from just after the rebuild 3 years ago. I have no way to know what oil was used or anything about it. So now I will be putting it into service in a month or so and have a few engine questons:

1. Do I treat rebuilt engines like new for break-in period?

2. Is there a different oil or additive for break in period?

3. I think I'll change the oil before putting into service as I want to know what's in there NOW. When do I change it again? 10-15 hours or just wait until next season like most marine engines used 3-4 months per year?

4. 6 qts. for a 454 big block right? My oil pump is a 5 qt. capacity.... darn.



Thanks.

1. This depends somewhat on how they were built, what kind of rings, etc... to be safe, i would run them easy for as long as 10 hours or so, varying rpms a lot (no running long time at single throttle setting)

2. Run Rotella T with a quart of lucas break in engine oil additive or something simila just so it has a high concentration of zddp or similar. I'm assuming that you have flat tappet cams. To be safe, this is what I would run for the duration.

3. I would statrt it, warm it up and then dump the current oil and put the above in. then change it again after 10-15 hours as you mention and run it like you stole it. I change oil more often than most, but whatever you're comfortable with after that.

4. You want a standard capacity oil pump. High volume oil pumps can empty the oil pan on extended runs at high rpms... when the oilp pump starts sucking air with the hammer down things start to suck in a hurry.

Finally, note that there are as many opionions as there are people to ask. I'm just going by my experience / understanding.

Hope this is helpful.

 

[tmh]

Re: How to break in rebuilt big block mercruisers/

Thanks for the tips. The Lucas break-in addative is what I was wondering about mostly. Is "Rotella T" a brand of oil? Is this OK for break in regardlessof the various factors.

When I said I have a 5-qt oil pump ...bad wording .. I was referring to my the capacity of my pump out device for changing the oil on the boat. It holds 5 qts so a 6 qt. engine would be too much to pump out for the change.

 

[Mkos1980]

Re: How to break in rebuilt big block mercruisers/

Empty it at 5 quarts and do it again for the other quart.

 

[flargin]

Re: How to break in rebuilt big block mercruisers/

I just finished breaking in an 89 454.

Attached is the oem recommendation from the manual. PITA to keep the RPM's moving and in the correct range for 20 hours, but boat feels strong now!!!

Good luck

Oh yea, in point 2, I don't have a clue what merc defines "extended period of time" we use 5 minutes early and 15 minutes later on (10+ hours).

a good radio and plenty of liquid on board is needed for a 2 hour break-in session, they are boring!