Home › Forum › Ask A Member › Low compression in bottom cylinder › Re: Low compression in bottom cylinder
April 24, 2018 at 9:57 pm
#74687
quote Dan in TN:
I would give the motor a good dose of Merc Power Tune or OMC/BRP Engine Tuner. It will remove carbon from the rings & combustion chamber. Let it sit overnight, but no,longer than 24hrs.
I believe the earliest version of this motor was a chrome bore? Later it became a Merc A Sil block. The chrome bore has to be sleeved if it was damaged, but a cylinder can be cleaned with myratic acid if just some aluminum has transferred from the piston due to a slight overheat? Unfortunately no cylinder head! Complete tear down to get there for that repair. Most likely going to want to replace the piston/rings on that cylinder. The later Merc a Sil block is not so forgiving. It can be bored once .015 with Merc pistons, but Wiseco offered a .030 also. This is a very light block. Good running motor & easily carried, but not forgiving at all for slight overheat or run with improper oiling. Keep you cooling system in top notch condition!
The motor can be sleeved & we did a bunch of them. Expensive, but makes it even a better, more forgiving engine. A tad bit heavier, but oh so heartier. Engineers get into a pushing contest to see who can build the lightest motor.
I believe the earliest version of this motor was a chrome bore? Later it became a Merc A Sil block. The chrome bore has to be sleeved if it was damaged, but a cylinder can be cleaned with myratic acid if just some aluminum has transferred from the piston due to a slight overheat? Unfortunately no cylinder head! Complete tear down to get there for that repair. Most likely going to want to replace the piston/rings on that cylinder. The later Merc a Sil block is not so forgiving. It can be bored once .015 with Merc pistons, but Wiseco offered a .030 also. This is a very light block. Good running motor & easily carried, but not forgiving at all for slight overheat or run with improper oiling. Keep you cooling system in top notch condition!
The motor can be sleeved & we did a bunch of them. Expensive, but makes it even a better, more forgiving engine. A tad bit heavier, but oh so heartier. Engineers get into a pushing contest to see who can build the lightest motor.
Dan in TN
I totally agree…. pick up a can of Quicksilver PowerTune, and use per the directions. It may be the best money you could spend on your motor. Recheck compression after a water test. Otherwise, if you have an inspection camera, you could look into the cylinder and check for damage. I use PoweTune on just about every outboard that comes through my shop.