Madcap

[lftmx3]

If you've been running the 402 in a trash can you need to check the grease and make sure it isn't getting contaminated, as well as checking the grease in the tailcone bearings. Do a search on maintaining the "D" quicksilver lower unit and you'll see what you need to do, but after each couple of days of use or if it isn't going to be run for a week or more you'll need to be checking the grease in the lower unit and using a grease tool on the tailcone bearings. If you leave water in the tailcone or the lower unit it will make a mess of things in short order.

yes I have been giving the cone a pump or two of cornhead grease after each run. This was recommended by Ron Thomas when he serviced the unit last winter. What should I be looking for as far as signs of contamination?

[johnsonm50]

yes I have been giving the cone a pump or two of cornhead grease after each run. This was recommended by Ron Thomas when he serviced the unit last winter. What should I be looking for as far as signs of contamination?

Water does get into these units, as long as its well greased & being used it doesn't get a chance to settle on any steel & begin the rust/pit process. That's why they go bad quickly once not used & not checked. The zerk fitting is good for short term protection but you should remove the cone [backwards thread], clean, dry & re-lube the cone bearings for long non use times. Remember the lube in front of the water pump is separate from the cone bearings. In short, water is what to look for whether mixed in with the grease or droplets on the parts it should be changed- both places regularly.

[1100-one]

Like Mike said water. It will turn oil milky color, Also when you drain oil look for an metal flakes. Last to check when you grease it look for any sand residue and clean well

[ZUL8TR]

yes I have been giving the cone a pump or two of cornhead grease after each run. This was recommended by Ron Thomas when he serviced the unit last winter. What should I be looking for as far as signs of contamination?

Since you said Ron Thomas did the gear case service he uses a special grease in the gear case (not talking the outer cone bearings here). Therefore it is not easily drained and a PITA to remove but it will still turn very milky with water. Personally I do not like the grease and when I bought my 25ss back in 1973 from Dick O'Dea it came with gear oil and that is what I always use, it is easy to drain out and replace. Still have that Merc and it has seen a huge number of race heats, testing and now at AOMCI wet meets and still has the original gears and inside bearings as well as cone bearings and the original cone nut, but I have replaced the seals a few times and replaced the impeller once. I use a synthetic 75w 90 gear oil like Royal Purple Max Gear or Mercury High Performance Plus, there are others. I changed often after each use and also pull the rear cone off and wash out and re-grease the cone roller bearings. I have a grease tool for the outer cone to pump shots during use. I use John Deere Corn Head grease in the outer cone, good stuff.

I believe the factory used the 105 grease because it had less chance of leaking with the seals used. I still use the same CR seals and no problems with the gear oil and change seals when there is a slight hint of a milky color in the gear oil. In my experience the drive shaft seal is usually the first to get sloppy.

[ctpdsr]

What are you using to adjust & measure the setup (motor angle)? What is the propshaft height when the motor sits flat on the transom AND parallel to the bottom? We ran 3/4" at the end of the prop shaft, but while tucked in with regard to setup angle.

[Yellowjacket]

Since you said Ron Thomas did the gear case service he uses a special grease in the gear case (not talking the outer cone bearings here). Therefore it is not easily drained and a PITA to remove but it will still turn very milky with water. Personally I do not like the grease and when I bought my 25ss back in 1973 from Dick O'Dea it came with gear oil and that is what I always use, it is easy to drain out and replace. Still have that Merc and it has seen a huge number of race heats, testing and now at AOMCI wet meets and still has the original gears and inside bearings as well as cone bearings and the original cone nut, but I have replaced the seals a few times and replaced the impeller once. I use a synthetic 75w 90 gear oil like Royal Purple Max Gear or Mercury High Performance Plus, there are others. I changed often after each use and also pull the rear cone off and wash out and re-grease the cone roller bearings. I have a grease tool for the outer cone to pump shots during use. I use John Deere Corn Head grease in the outer cone, good stuff.

I believe the factory used the 105 grease because it had less chance of leaking with the seals used. I still use the same CR seals and no problems with the gear oil and change seals when there is a slight hint of a milky color in the gear oil. In my experience the drive shaft seal is usually the first to get sloppy.

All good advice... In particular the part about changing the seals frequently. The standard seals without springs are designed for only a 3 psi pressure differential. What happens is that the pressure developed by the water pump and by running through the water is a lot higher than that . This higher pressure pushes the sealing lip harder onto the shaft and causes premature wear of the seal. Seals with springs are no better since, while they seal better at lower pressure, the water pressure on the inside still causes premature seal wear.

What would solve the problem would be what is called a "higher pressure" seal. These are stiffer and have a shorter length between the case and the seal lip so that pressure doesn't push the seal lip onto the shaft and cause it to fail in such a short time. Unfortunately no one makes them in this shaft size and outer diameter. I looked into having some custom made but they were crazy expensive, a couple of thousand dollars for tooling and $40 per seal, which I don't think may folks would pay for them even if they lasted longer and had lower drag than the OE seals..

I have found some seals that may work with modification to the housing and I'm going to try them this season. They are rated for 13 psi, which is much better than the OE seal, but they may not work all that well since the pressure is likely higher than that.