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Old 07-20-2013, 04:11 PM
j.mccreight@hotmail.com's Avatar
j.mccreight@hotmail.com j.mccreight@hotmail.com is offline
MC Maniac
 
Join Date: May 2010
Boat: 1989 MasterCraft TriStar 190 SE
Location: Houston, TX
Posts: 3,305
Yes a normal motor will show 10-15% leakage, your numbers are mostly good, cylinder 8 is iffy at best, I would start looking at #8, anything above 15% and you need to start thinking about investigating and possible rebuild. I recently did a leak down test on a 5.6L titan with 135,000 miles none were over 8%. I would clean top end, pistons etc. Mix up some atf/ water mix 50/50, (marvel mystery oil can also be used)remove all spark plugs insert several teaspoons full of mix into each plug, let soak for 10-20 minutes while slowly rotating engine over by hand every few minutes, then spin engine over with starter motor, plugs still out to remove excessive atf mix, install plugs, it will smoke like a chimney until all atf is burned off, run it for a while, let cool down a bit and recheck leak down warm.
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1989 MasterCraft TriStar 190 SE

Last edited by j.mccreight@hotmail.com; 07-21-2013 at 09:22 AM.
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