1999 Mercury 9.9ml lower end problem

was out fishing this weekend and friday when i took off from the ramp the holeshot felt like it was cavitating ... its a 9.9 LOL .. anyway it progressively got worse over the weekend until it let go and stopped pumping water when it did ... it goes into gear forward and reverse .. you can make it slip when you turn the prop by hand .. its like it has a 2 piece drive shaft and the coupler is slipping .. any thoughts would be appreciated.

when the prop is slipping is flywheel not turning ..I was thing about not pumping water if drive shaft not turning it wont pump water

keelme said:

when the prop is slipping is flywheel not turning ..I was thing about not pumping water if drive shaft not turning it wont pump water

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its like there is a clutch on the drive shaft and it slips, it goes into forward and reverse fine .. but the water pump stopped working when it did it the last time ... when you come out of the hole we thought at first it was cavitating .. but as time went on it got progressively worse until it wont push the boat at all and no water pumping ... going to tear into it tomorrow .. i gave 1000 for the motor and i honestly do not want to put more than 250 more into it ...

well the lower end if fine it appears, but the drive shaft seems to be worn at the crankshaft/driveshaft connection ..... how could the shft be toast but not the crank? i mean they are both steel, so if ones trashed the other should be too?

Lack of proper servicing (lack of grease on the splines and no way to keep the grease in place) was probably the root cause however, to answer your thought process, even though they are "both built out of steel" they are very different steels! One is hardened and designed to live under very different loads than the other. The failure actually happened as it was designed to happen.
Another remote possibility for your failure if your splines are stripped on the driveshaft is that the exhaust housing is slightly bent. Without proper tooling and measuring equipment the only way to check for this is to pull your powerhead, install the lower unit with driveshaft and see where the top of the driveshaft is. If centered, great....if not, not so good.

thanks for the reply pappy .. wold be great if ya could just slip the drive shaft out, but the local dealer said it would require a tear down, they want to charge 500.00 to do the drive shaft .. so i'm looking for a local mechanic. major bummed out

well i pulled the drive shaft .. no problem .... now a parts order and she's back in service hopefully, its looking like about 300 in parts. all in all its still cheaper than buyin a new motor, i trust my old merc and by doing my own work i know its done right and not jury rigged!! these should be straight splines i believe ... not helical LOL