85hp Crankshaft Seal

[mbruce333]

I dropped the lower unit yesterday for a little water pump work and realized that the lower crankshaft seal has been blown out. The metal retainer (that looks kinda like a cricular spring) was at the bottom of the driveshaft sitting on top of the water pump. A quick check with a flash light shows 1/2 of the seal hanging down from the power head. Major bummer.

So, my question is what to do about it. Can this seal be changed without breaking the block open and removing the crankshaft or can I pull the power head off the leg and get at it from the bottom?

The power head is a 1974 mounted on a 79 leg, btw.

Thanks guys!!!
Mike

 

[jerryjerry05]

Re: 85hp Crankshaft Seal

Think you have to pull the head and the seal can be accessed from there.
Don't think it has to come all the way apart.J

 

[Frank Acampora]

Re: 85hp Crankshaft Seal

The spring is a Garter Spring and compresses the seal lip against the crankshaft. The seal itself is pressed into the bearing shell and may or may not come out-- I have never needed to try. At any rate, if you need to replace the seal you must remove the powerhead UNLESS you have long tools to reach up and pull the old seal then press in the new--not!

BTW I have LOTS of the bearing and seal combos but I do not have the seal only. You do need to split the block to replace the bearing and seal assembly.

 

[mbruce333]

Re: 85hp Crankshaft Seal

Thanks for the info!

What would be the effect of running the motor with a seal that's not, well...sealing so well?

I just put this powerhead on this leg 6 weeks ago, or so. I used this powerhead last year on a leg with a 2-piece lower and the boat was a ton of fun, great power and top speed. This year I was able to pick up a 1-peice lower, 2:1 gear ratio, Stainless steel prop and I had high expectations for improvment. I've only had it in the water a few times so far this summer and the performance has not been that good. Lower RPM at wot, lower top speed, weak hole shot.

Could this motor be leaking air in through this seal and keeping it from reaching wot? Perhaps I just found the reason for my 85 that feels like a 60hp!

Mike

 

[Frank Acampora]

Re: 85hp Crankshaft Seal

Well, that bottom roller bearing has a lot of clearance between the rollers so oil and crankcase pressure will blow through, reducing the charge delivered to the cylinder. Yeah, it will make a performance difference--how much? I don't have that experience. I suspect that radically unbalanced power pulses may do some harm. At a minimum there probably will be more vibration--These engines vibrate a lot so you may not notice it. Since, if I remember correctly, the fuel pump also has one stage pulsed by the bottom cylinder, reduced pumping efficiency (alternate pressure and vacuum) will also affect fuel pump output to some degree.

However, as I have proved in the past, (Search my posts) the one piece lower unit is about 2-3 MPH faster than the two piece lower. AND-- The 2 to 1 ratio lower also gives more top speed if compensated with a higher pitched prop. Thus a loss of performance, if no other factors are observed, will be directly attributable to the blown seal. Do NOT discount the different prop. An incorrectly propped engine will show the symptoms you describe.

Bite the bullet and remove the powerhead. If you can find a seal, replace it. If you can not find a seal contact me in a PM. I will give you a good deal on a bearing/seal assembly.