Motor Break-in

[Dave M]

Idle Hour

One of the things I see happen most often is people who are not as in tune with Mod engines as others using a synthetic oil. The rings won't seat very fast if this is done. So on everyones list should be using real oil.

For Merc's our break in is similar to most. We typically put it in our test tank, without a load and fire it up for a bit and heat everything up to temp and make sure all the seals are holding, from exhaust, to water, to carbs, and everything in between. This is basically a see if it runs right run, takes about 10 minutes maybe 15 depending on the water temp. But it is important in my opinion to make sure everything is sealing right. A ton of power is lost if it is not. After it cools down to ambient temps we fire it up again for about ten or 15 minutes and bring it up to temp. We don't rap it up to full RPM, but we do rev it now & again. At this point I would really prefer to take it out on the water and load it for about 5 - 10 laps. But this is not always possible in winter around here. So we run it another 15 and rev her up good.

We do it different for the OMC's, but basically the same. Depends on a number of things on each engine though.

One thing is for certain, your engine will get faster when it breaks in, and it won't be from your break in period. Mid season she will start coming on.

[David_L6]

One (maybe both - don't remember) of Harry Brinkman's books has some information about "break-in".

I was lucky in that I had a test tank available and it was not near any other houses. I ran my motors in the tank for a bit before I ran them on a boat (newly built motors).

I'd run it until it was warmed up completely with a light load (old small prop), never revved it much and squirted some gas oil mixture in the carbs while it was running to make sure it had plenty of lubrication. I never had a test wheel so I used old two blade 1:1 A or B props on my 1:1 C motors and whatever I could scrounge up that would fit a D lower unit on my D and E motors. I don't like the idea of running a new motor with absolutely no load to start with but I don't want much of a load either. After that first firing I let it cool down completely (usually over night). Next day I'd run it a few more minutes on the tank still not revving it all that much. Sometimes I'd run it two or three times - warm it up completely and let it cool between runs. Just depended on how much time I had. I always had needles adjusted rich when running on tank and I used my regular gas/oil mixture. After that I ran it on a boat for a few minutes with a prop that planed easily. Fire and warm up motor a bit on the cart. If you are using a lower unit with a water pump all the more better because you can run it longer and warm it up really well. Just a lap or lap and a half is about all I ran it for "break-in" on the boat. At this point I'd rev it pretty good but not for extended periods then come in a let the motor cool down. After that I'd run it again and run it wide open all the way down the straights this time. I figured it was good to go at this point.

It helps a lot if you already know where to set the needle valves. If you don't know you have to run it on the boat enough to get needles set. I ran one set of carbs on several different C motors. In fact, I ran that same set of carbs for several years with a needle that was broken off just outside of the packing nut (needle got bent by spray shield when I flipped my C runabout and broke off when I tried to straighten it)! I ran swinging mags so I didn't have to worry with setting the timing low like you would if you run an anchored mag.

I had some old TCW2 non-synthetic Castrol brand outboard motor oil that I used for "break-in". I ran synthetic for racing.

For a re-ring only I liked to run motor on boat with dino oil for a couple of laps before I switched to synthetic. However, I have been short of time and the rings got seated while milling and on the way to the first turn. ;-) I didn't do much of anything different for just a re-ring other than running non-synthetic oil for a few minutes.

[hydroman6]

Cheap little fix I use to keep the neighbors from calling the cops while breaking in a mod motor

[Larry M]

Stop and think what is breaking in. Is the bearings being worn in , I don't think so. Is the piston being worn in. No you can check a piston that has been run 50 years and I doubt if it is 1/2 thousand worn. Running a motor at slow speed doesn't do anything except glaze the rings. The shape of the cylinder changes after it is hot so how is a ring going to fit perfect on a cooler motor. If the clearance are not right I don't care how much you idle a motor around it will stick. On a new motor I like to run a couple of easy laps to get the grease out then open it up. Put some pressure on them rings and make them seat. Ok fire away.

Larry Mac

[blueskyracer]

Stop and think what is breaking in. Is the bearings being worn in , I don't think so. Is the piston being worn in. No you can check a piston that has been run 50 years and I doubt if it is 1/2 thousand worn. Running a motor at slow speed doesn't do anything except glaze the rings. The shape of the cylinder changes after it is hot so how is a ring going to fit perfect on a cooler motor. If the clearance are not right I don't care how much you idle a motor around it will stick. On a new motor I like to run a couple of easy laps to get the grease out then open it up. Put some pressure on them rings and make them seat. Ok fire away.

Larry Mac

Larry it make sense to me.. And your stuff is fast too

[krazy karl]

Larry, no fire here. I agree with you 100%.
kk

[Dave M]

Rituals

It is like a ritual, everyone has their own unique way. I know guys who break them in for a few hours in a test tank.... I know some who never fire the motor until the three minute gun goes off, and they open her up.

I honestly think it is more about your skill set as a builder and your level of confidence in yourself. If you have a set of carbs that you know work, filler blocks are always sealed, etc, etc, there is no doubt you will break it in faster than one who has less confidence in themselves.

I have seen both types of break in engine methods win races. Mac can certainly say their methods work, look at the long list of championships they have, in more than one Merc class. You have to respect the fact they can back up their words with wins.

[larry herman]

run a few marathons

[form-e one]

just broke in a d-mod at lawrence 2 little dry fires then full tilt raceing,,, runs great,,,

[modracer7b]

For about 50 years through numerous classes, stock and mod we had one break in procedure.
Set it up in race mode, make sure the water is pumping and run it like your heading for the first turn for two or three laps. If something doesn't work right, then it needed to be fixed anyway.

My 66 nationals A broke the crank testing the day before eliminations and we had to take parts from a spare engine to put it together that night and break in was milling for the start. Won the eliminations and the finals with it.

Bill Rosado

[pearson95m]

break in method.

step 1. put motor on boat
step 2. put prop on motor
step 3. put boat in water
step 4. Green Flag

Slightly exaggerated, but not far off the truth.

[blueskyracer]

Ok all Mod engine folks what would cause a new engine to run on cylinder 1 and 3 but 2 and 4 are wet with fuel.. And yes all plugs are sparking when we took them out and tested the ignition system.

[Yellowjacket]

Ok all Mod engine folks what would cause a new engine to run on cylinder 1 and 3 but 2 and 4 are wet with fuel.. And yes all plugs are sparking when we took them out and tested the ignition system.

Too much fuel... It's puddling in the intake and reed cage and flooding the bottom cylinder on each reed cage.

[hpick86n]

yer reed block lambrinth seal is worn out and you lost your primary compression.put new reed blocks in and you will be runin on 4

[blueskyracer]

yer reed block lambrinth seal is worn out and you lost your primary compression.put new reed blocks in and you will be runin on 4

This is a brand new motor with new reed blocks.. New pistons rings bore job the whole nine yards and new reeds