Re: buying a lower-unit..need advice
First, work on the assuption that you will need to replace the seals and water pump impeller (if it comes with a water pump.)
Look at the outside of the case. Is it in generally good condition, consistent with its age and price? Is the skeg bent? A little or radically? Has it been newly painted with a thick coating in an effort to hide corrosion? If it shows salt water corrosion, go on the the next one; It may be good but down the line if you need to do repairs it will be a hassle. Does it have lots of chips, dings, and nicks indicating possible hard use? If you can look at the prop, does the prop show wear and dents/bends indicating hard use? Grab the prop shaft tightly and push in hard then pull out. there should only be very slight movement (say about .010 inch--not sure of specs on a 93) with possibly a faint audible click. If the shaft moves a lot--say 1/16 inch or more, reject the unit.
Take an old prop with you and just slip it on the shaft. Rotate the shaft in neutral --it should be silky smooth. Any grinding either in neutral or in gear, reject the unit. Look for wobble indicating a bent prop shaft. If wobble is present, reject the unit. Work the shift rod. It should be snug in the seal but not tight enough to bind -this is not a reason to reject the unit though. It should however go into both forward and reverse gear quite nicely wwithout binding--however, you may need to rotate the prop to get it into gear. Now rotate the prop in the correct direction for the gear chosen--remember, the drive shaft should always turn clockwise when looking down on it. Since you are loading the gears in the opposite direction of normal, you will hear a slight gear noise if the water pump is removed; with the water pump on, you will hear the impeller rotating and may or may not hear the gear noise. However, you are listening and trying to feel for a skip due to a broken gear tooth. Drain some of the oil and look at its condition. Milky indicates a water leak and you can be sure you will need to change at least one seal. It is not a reason to reject the unit but is a bargaining chip for you. Gritty oil indicates wear and you would not want that unit. Fresh oil? --It's a crap shoot. I have seen old units where the oil looked new. If the owner changed the oil, why? Not a reason to reject the unit unless other tests indicate it. I personally would rather see old black oil in good condition that I need to change.
Also, do not buy a unit with 1.78 to 1 gears. your Force should have 2 to 1 gears (if it is not a Merc midleg and lower unit--I am not sure what year Merc actually changed them) and will lose performance with the higher ratio gears. If the owner doesn't know, mark the prop and turn the drive shaft twice. the prop should turn only once --NOT about 1 1/4 turns. Merc lower unit is completely different so if it looks like a Force lower, it is. --You Know! If it has webbed feet, a bill, and waddles, and looks like a duck, then it is a duck.
The rest is luck. PS. See my private message to you.
