1986 Merc 25 12Footer check my response

[FatBack]

My gasket kit came with a sleve for the lower crankshaft. There wasn't one on it when I took it apart. Could this be my low compression problem. New engine to me. Lower oil seal leaking and crankcase not holding pressue. I Just thought of something. The sleve may have come off and slid down the driveshaft to the foot. What do you think.

 

[12Footer]

Re: 1986 Merc 25 12Footer check my response

It sure could have.<br />One important note tho...some gasket kits fit muliple models/years, so don't be too allarmed if you have a few "left over". I seldom use all gaskets anyhow, unless it's a total tear-down.And many times, this is more trouble than it is worth ( "if it aint broke" school of thought).<br />But I'll bet you are right, (about it sliding down on the shaft).

 

[FatBack]

Re: 1986 Merc 25 12Footer check my response

Hey 12Footer, Mercury's microfish shows this sleeve and calls it a crankshaft seal. My manual shows it but it's not labeled nor does it mention anything about it. This engine,when it was runnig, only operated at half throttle. Everthing,and mean everything else checked out OK. Could this seal cause pressure leak relates to only exactly 44lbs. of pressure on each cyl?

 

[12Footer]

Re: 1986 Merc 25 12Footer check my response

Perhaps. If it was gone,I would think you would loose ALL crankcase pressure. But I've never seen one completely disapear. Maybee it was pressurizing only on the internal stroke against the reeds?<br />I've seen seals burn up, but there were still scorched marks and clumps of rubber everywhere when it did.<br />did the motor run for a long time with poor performance? Usually, when you loose that much compression. the thing just would not take you fishin.

 

[FatBack]

Re: 1986 Merc 25 12Footer check my response

12Footer,<br /><br />This has been the most challenging problem I ever had with and engine. This seal thing is the only possible thing I have found wrong with engine. It runs just fine till half throttle. It did it with the owner before me and he gave up on it after several attemps to fix it. Exhaust was coming out of this seal when the engine backfired once during carb adjustment after rebuild. That clued me to look at the lower seal on disassembly. The rings and cyl walls all look good. The engine shouldn't even run on 44lbs.Read pressure on three different gauges. All the same. Anyway, anymore thoughts would appreciated.

 

[FatBack]

Re: 1986 Merc 25 12Footer check my response

12 Footer,<br /><br />Also, the lower seal looks fine. I just thought it might have been in upside down. Hopfully tomorrow I'll fine that crankseal lying on top of the water pump. Thanks for your help.<br />I'm out of here. The Bird