MAKING THE SEAL ON WET HEADBOLTS & STUDS
40 to 50% of our business is hi-performance boat engines, and the head bolt/stud sealing is critical on these engines. Jet boats use “waste” water from the jet pump to cool the engine and the pressure applied to the water jacket can easily exceed 50-70 pounds with a fast boat! Inboard/outdrive prop boats pickup lake water at pressure ports in the lower unit, and the impact pressure varies with speed, but will exceed one pound per mile an hour at speeds above about 75MPH, which today is an entry level performance boat! We have tried many methods and sealers to keep water out of the oil on engines with “wet” head bolts. The best solution we have found is to tap the bolt holes in the deck with a new tap and tapping fluid, then spray each hole with brake cleaner and shop air to dry and remove any remaining dirt and rust. We use a Phillips screwdriver to apply a high quality stud sealant, this is not the time to buy cheap pipe dope at the hardware store. You want a sealant that is consistent in its viscosity and particle size. We completely fill the deck threads to the minor diameter of the hole, taking care to coat every thread and then we remove any extra sealant from the deck with solvent. We put a dab of sealer on to the threads of one bolt and take another bolt and roll the threads together to evenly distribute the sealer to the entire thread. The goal is to keep water from finding a path between any gaps in the sealant. After more than 25 years, we haven’t had a single leaking head bolt or stud.

Timm Jurincie
Tuf-Enuf Auto & Marine Performance
Avondale,AZ.
May, 2016