leakdown ?

[bec]

did a leakdown on a nic motor and i got 5% on 1 6%on 2 4%on3 7% on4 5% on 5 and6% on 6.motor has 60hours on it.iborrowed a borescope and looked down in the cylinders and no 4 i have a concern about the cylinder wall it seems to have several scuff marks in the cylinder. iam going to wipe off the injector orings as i have noticed a little wetness around a couple of them but is not bad enough where they have started to get residue on the block.should i pull these heads and have a closer look.my stupid self has been replacing plugs in this motor several times between 25 and 50 hours with the same cheap plugs and sometimes they would foul so bad the boat would not even get on plane. 52 hours or so and start running br8hs in this motor.i know i have been out there a few times with the cheap plugs in my motor would take several feet before it cleared up and would get on plane.and i do mean several feet. do you think i have self inflicted these scuff marks by running on fouled plugs till they clear up .my motors lower unit and prop hub used to get so black it wasnt even funny.to date i have had all injectors flowed tightenend every connector possible ,changed over to ngk,was going to go with dukas reeds and decided not to change the reeds because the tolerance on these reeds were acceptable buy the merc manual told jay i was going to buy some and never did call him back and i apologize but after pullin these reeds i did not see any since in replacing them no cracks or chips and under 10 thousandths,adjusted tp sensor ,adjusted butterfly air gap adjusted crank sensor found one coil pack with a corroded tower and replaced it.change fuel filters religously along with waterfuelfilter,fuel never stays in this tank over a months time witout draining it.i posted a while back how awesome my boat was running and now it has gotten where it is falling on its face again.

[wrechin2]

I found out the hard way...... Do not do your leak down at TDC but find TDC using a screw driver. mark it then go 3/8" toward the handle and mark it. Find TDC and roll down 3/8". If you have any damage in the cylinder you are at the top of its travel and will show low leakage. I have found countless problems doing it this way. I love showing the customer at TDC it has 7% roll it down and find 75%. Pull head and have it scuff severly. JMO. Hope this helps!

[bec]

thanks for the reply i will try that.using the leakdown tester is not as bad as i thought it would be as long as you go by per instruction of balzy and other people here on the forum.i can see it getting hairy though if you had it already regulated to 90 to 100 and decided to hook it up.i really like the balzy leakdown tester.i used it a couple of weeks ago and found a intake valve seat cracked the other day on a ford focus2.0 liter as these things are notorious for dropping seats.

[wrechin2]

ALWAYS use 2 people when you roll it 3/8". It will go one way or the other and you will EAT a breaker bar. I do so may on mercs, I am going to make a tool to hold it once I get it where I want it and can do by myself. I always have to explain to customers that even though it has COMPRESSION does not mean it is ok. Compression=ability to make pressure. Leakdown=ability to hold it. I could not tell you how many engines I have rebuilt that the customer has performed a compression test on and stated it wasn't mechanical. Then do a leak down, pull head and show damage. Sometimes it is coking of the rings that cause it. OMC x-flows are bad about that or in-line mercs. Hope this helps. BE CAREFUL

[DoferGofer]

What is the best way to physically check the carbon build up in a OMC Cross flow, remove the heads or remove the exhaust back plate? I plan to physically (eyeball) check the health of my engine soon.
So, which would you pull first?

:o