possible bad lower crankcase seal , 1969 55hp 3 cyl

[Buckstr]

Hi all<br /><br />This engine started to stall when given throttle but ran fine at high rpm, slowly got worse and now only runs on muffs in the driveway. I have checked comression, about the same on all 3 cylinders (90 psi), it has spark as tested with spark tester, and, since I did not know what else to do, I have rebuilt carbs (twice) and replaced the powerpack with an auto ignition coil but still same problem. I have now noticed that the lower (# 3 cylinder is not firing at idle speeds on muffs in the driveway) When I put my hand in front of the carbs, I noticed good sucition on the top cylinder, ok suction on the middle cylinder and no suction on the bottom cylinder. I can squirt premix into this third cylinder and it just pools there in the front part of the carb. Since compression is good, I am suspecting the lower seal on the crankcase. <br /><br />Is there some better way to diagnose this before I start pulling off the powerhead? <br /><br />All help is greatly apprectiated.

 

[Buckstr]

Re: possible bad lower crankcase seal , 1969 55hp 3 cyl

Well, looks like I am going to try to replace this seal. My crappy SELOC manual is wanting in descriptions but from what I can tell, after I disconnect the electrical and throttle cables, I should be able to simply unbolt the powerhead from the exhaust housing and pull it free and have access to the lower seal. <br /><br /> My manual says I need to remove the flywheel, Is this necessary? Seems like the lower unit should easily seperate from the the powerhead without removing the flywheel.<br /><br />Any thoughts on this would be great. I Will keep you posted on how it goes in case anyone is reading this.

 

[boatmoter1]

Re: possible bad lower crankcase seal , 1969 55hp 3 cyl

I don't believe the seal is your problem..<br /> the other two cylinders are firing, if the seal was leaking, the engine could not create enough <br />vacum to pull fuel to top of pistons.<br />it would not fire on any cylinders or run..run a compression test.. if that checks good,check the reeds..

 

[Buckstr]

Re: possible bad lower crankcase seal , 1969 55hp 3 cyl

Boatmotor1<br /><br />Thanks for reading and responding. You are probably right. However, did not see your post until I pulled off the powerhead earlier tonight. Original O-ring on the cap that houses the seal looks about 2 sizes too big, not sure if that could be the cause, seal itself looks ok but will probably replace just in case. Now if I can find the parts ( O-ring, seal and gasket for powerhead to exhaust), plan to check NAPA to see if they can get them for me.<br /><br />I did check the reeds prior to all this. They looked fine when I poked them, seem to move and not be stuck. Once I get it back together, will update and let ya know if this last attempt has helped.

 

[DHPMARINE]

Re: possible bad lower crankcase seal , 1969 55hp 3 cyl

Buckstr,<br /><br />My calculations for the parts you need :<br />330137 seal<br /><br />308876 oring<br /><br />313763 gasket<br /><br />Your NAPA Dealer can probably convert these to his (Sierra),but also think about keeping your local Johnson/Evinrude Dealer in business.<br /><br />DHP