crankcase- depression under lower crankcase oil seal

[ryanc]

Hello again, 1973 merc 200 20 hp. Initially if you remember - I had a ball bearing blow out in the crankcase, I noticed there was what appeared to be a chipped away section on the lip where the oil seal sets within the crankcase, I took for granted that the bearing had did this damage.<br /><br /> Today I took apary another power head (same one bought off ebay) and noticed that this caing also had the same depression under the oil seal. Does anyone know what the function of this is???? thanks again robert/ryan

 

[ryanc]

Re: crankcase- depression under lower crankcase oil seal

thanks for no help everybody

 

[Mettaree]

Re: crankcase- depression under lower crankcase oil seal

Ryan: I've never had the PH off my '79 20hp so there was no need for me to chime in. Sorry you feel like you are being ignored - someone out there knows the answer and will let you know.<br /><br />

 

[ryanc]

Re: crankcase- depression under lower crankcase oil seal

thanks Jkw for your reply, as i had a ball bearing blow out in the crankcase I thought that this depression was a chipped out area caused vy the loose ball bearing. I plugged the depression with some JB weld and reshaped the area for the oil seal to set on.<br /><br />As it turns out after the motor was put together I started having back pressure causing my recirculating hoses and fittings to begin to leak. I also found it was near impossible to get a good idle adjustment on the carb due to backfiring problems.<br /><br />In light of this I tore the power head down again and tore down a spare ebay bought powerhead and did a comparison. To be noted the ebay crankcase did in fact have a similair cut out on the rim where the oil seal sets just above the end cap. Today I drilled out the area that had been patched returnig it to its original condition.<br /><br />I talked to a marine mechanic today who could not give me an answer as the motor is 31 years old, but a friend has enlightened me with the fact of the oil seal allowing air to escape in one direction while keeping water from entering from the opposite direction. Surely with the recirculation fittings bubbling under high pressure the pil seal somehow must act as a valve for crankcase pressure as well as providing some lube for the end cap area. <br /><br />Anyway I am putting the powerhead back together<br />and hopefully my back firing problem and pressure problems will dissapear.<br /><br />Still it is kind of a wierd because the cut out or drilled out area of the oil seal rim is only partially cut away leaving atleast a 1/16in of rim for the oil seal to set on. The bottom of crankcase has a molded line 1/8 in deep and about 1/16 in wide that runs for about an inch that allows oil to lube the lower crank ball bearings on over to the oil seal. Just trying to understand the physics merc was employing here. Well, thanks for your reply