Mercury 9.8 drive shaft issues

[billy-t]

Hi All

Well finally got around to changing the impeller on the Mercury 9.8 and all was going fairly well until I noticed that the splines on the top of the drive shaft are badly worn. Doesnt look like this motor has many hours left on in! Are these still available? Likely pricey, better to look for a good donor motor I guess.

It didnt appear that there was any oring to keep water out of power head like on the Johnson stuff. Interesting.

Bill

[billw]

What year/serial #? There should be plenty of drive shafts, considering the number of bad gear sets and blown cases out there.

Long live American manufacturing!

[raglover]

I am not an expert on the Merc 110’s but in the few I have pieced together I did notice differences in shift shafts and such if you were not swapping an entire lower unit out, and on the shift shafts the upper portion had to be considered too. Not sure about the drive shafts but a check on marine engine parts diagrams could probably confirm the part numbers in matching years.

As for the worn splines, it may be a good idea to shine a light up to the crank shaft to make sure that it is not worn as well, or at least help you make a judgement call on what to spend.

Good Luck

[20mercman]

I have seen worn splines on the 200’s, but not on the 110’s. The drive shaft should be interchangeable for this motor from a lot of motors from 6hp, 7.5 and 9.8hp. On the 200 I had, I had to turn the crank against rotation of the lower unit to get the thing to let go, it was like a twist lock. The splines in the crank were fine, so it must have been a poor heat treating issue. This was on a 1969 motor, and I have also seen wear on the stainless shafts as they are softer then the carbon steel shafts. Don’t condemn a motor for just a drive shaft, as they are around.

Steve

[billy-t]

Thanks, I will look around for a drive shaft. Of course, everything is less plentiful here in Canada as there is less of us and less motors too.

But perhaps some merc guys could enlighten me a little. If there are two different impeller sizes does that mean there are two different shaft alternatives out there too and are they interchangeable between motors?

Thanks I do appreciate the advice of those that do know more than me.

Bill

[jeff-register]

Dave B where are you? Dave is a great guy for driveshaft & anything Mercury relted. Isn’t there a cd out there on Mercs on what fits what? Have seen it somewhere, maybe JOM"S site I saw it.

[Doug Wilson]

was thinking there was supposed to be an O ring near the top to keep the water from getting there but would have to pull one apart to check.

Doug

how is it motors multiply when the garage lights get
turned off?

[Mumbles]

There’s a little piece of felt or something or a seal inside the end of the crank extension which is supposed to hold oil or grease.

One interesting note here. On one 9.8 I saw, the hole and splines in the end of the crank were machined right thru the crankshaft. The motor never did run right as pressure and vacuum were going thru the spline area.

[billw]

Yes, there are two different shaft diameters to match the three (that I know of) different impellers and the difference is only a few thousandths of an inch. There are many more variations of the shafts, depending on serial number. There are two ways to get the right part for a Mercury: Serial number or trial and error. With emphasis on ERROR. Save yourself some serious grief and shop by serial number and part number.

Long live American manufacturing!

[billy-t]

Okay so here is the information

Canada Serial number 7074683

It would appear to take drive shaft part number 75034 or 45-75034 depending on which site

it would appear that the same drive shaft should be found on motors in Canada with serial numbers 7049108 and up

Sooooo……. would i be correct in assuming that if i can find a parts motor with a serial number of 7049108 or higher it might have a drive shaft that would work?
suggestions

Bill

Thanks for any

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