got a new lower unit - need tips

[SkiDad]

OK, so due to my dumb mistakes I think i toasted the forward dog in my 1985 force 125. So I picked up a whole 1988 force 85 motor for 200.00 (carb issues). I have the lower off and it seems in nice condition and seems to shift good.

- the water pump housing looks really new - should I still change the impeller or don't bother ?

- I can't get the lower screw out to drain the oil - it's a smaller allen hole that my other lower and I can't budge it easily. I opened the fill screw and some fluid came out so it probably is full - do i leave or turn upside down to change ?

- what do I need to do just center the neutral on my engine - i know some have said that i need to bias a little to forward - i don't want to the same issue again so how to i make sure I have it aligned properly ?

- old LU was white and this one is black - will spray paint be fine to color it with ?

i guess the bright side of my mishap is that the new lower I'm putting in is 2:1 instead 1.73:1 - should be interesting to see what she runs like now. I was turning 5000 with my 15p prop - i'm guessing i might turn closer to 6000 now so I might have to pick up a 17p eventually.

anything else I should look out for ?

and Thank you !

 

[Jiggz]

If the impeller doesn't show any signs of cracking, there is absolutely no reason to replace it. However, unless you know how old the impeller is it would be wise to replace it now and every three years at the maximum or like me every two years since I only use the boat 3 months in a year. The drain plug may have been worn out but try using metric hex allen wrenches to fit and then replace the oil and plug.

As for setting the neutral, there is really no specifics except that it should not pop out of gear at high loads or speed in both fwd and reverse. You can define neutral from the shift rod (with the upper section disconnected from the upper section) by marking the farthest forward the rod will shift and also the farther point reverse and getting the median between the two distances. And when you connect the upper portion the travel of the lower shift rod (in respond to the control lever) should correspond to the markings including neutral.

 

[pnwboat]

Pretty easy to confirm it's a 2:1 ration lower. Put it in gear and turn the drive shaft. It should take 2 turns of the drive shaft to turn the propeller one revolution.

As far as the prop is concerned, the lowest pitch prop you'll want to use is probably a 17 pitch. I switched to a 2:1 unit off of a 1988 85HP motor and put on my 1988 125 motor. With a 17 pitch stainless prop, I turn 6000 at WOT. Great hole shot for heavy loads (200+ pound Slalom skier). If I'm cruising long distance I use a stainless 19 pitch prop which gives me about 5600 RPM's at WOT. Your set up may not give you the exact same RPM's but it should be somewhat similar results. For my particular set up, the 2:1 ratio resulted in a big improvement with the hole shot.

If you think that the drain plug is going to strip out, then you can do as Jiggz suggested and try a metric allen wrench. I stripped mine out so I just drilled it out and used the next largest pipe plug size. Not a big deal, just make sure you use at least solid cobalt steel drill bit. High speed steel, cobalt coated, or Titanium nitride coated drill bits are not as good. The good thing about going to the next larger pipe plug size is that there is more meat on the plug and larger allen wrench so it looks like it'll take a lot more effort to strip it out.

Just because the water pump housing looks new doesn't mean the impeller itself is in good shape. I'd get a new one just for piece of mind. They're fairly inexpensive and if it fails, it's a show stopper.

 

[SkiDad]

i confirmed the 2:1 ratio when I took it off and it matched the 3 that is stamped on the side

the PO helped my on the last water pump change - we just got the whole kit (housing and all) - can I get just the impeller or will I need to get a gasket too if I open this up

what are the inch pounds torque for:
- 4 water pump bolts ?
- 7 bolts that hold lower unit on to leg ?

the drain plug seems to take a 5/32 allen - i yanked on it pretty good and it's not budging - my other lower has a bigger screw that I put the rubber seals around. With the crazy year I've had I'm tempted to leave it but that makes no provision for checking for water in the oil before I put it away this winter.

 

[foodfisher]

Got mine out by putting pressure on the allen wrench then tapping on the bend with a hammer. Like an impact hammer

 

[pnwboat]

The impeller "kit" that has the impeller, gasket, stainless wear plate and new bolts. There are two versions. You can tell which one you need by the gasket. To be 100% sure, you have to look at your particular set up.

Typically the one piece drive shaft lower use this kit.


The two piece lower units usually use this one.




70 inch pounds on the water pump housing bolts

Lower unit to motor leg: If you have 5/16" X 18 bolts, 160 inch pounds. If you have 3/8" X 16 bolts, 270 inch pounds.

 

[Frank Acampora]

One old salt told me that sprinkling a little abrasive sink cleaner into the allen head will keep it from stripping. I don't know, I never tried it. You can also try tapping in a Torx bit and using a socket driver. The appropriately sized Torx is just a tad larger than the allen wrench. HOWEVER: Some of those scres are really tight. Last time I tried this, I stripped both the screw and Torx bit

By the way: If you remove the anode and the two bottom spool bolts, oil will drain from there. You don't ABSOLUTELY need to use the drain plug. It is more convenient though.

 

[SkiDad]

By the way: If you remove the anode and the two bottom spool bolts, oil will drain from there. You don't ABSOLUTELY need to use the drain plug. It is more convenient though.

Do I need to replace any washers or seals if I do it this way ? Would I see water this way ?

 

[SkiDad]

No Title

i took the water pump of and the sides are perfect (not a mark) - impeller looks brand new too. there is some scoring at the top of the housing - anything to be concerned about ?

 

[pnwboat]

Looks like it's in pretty good shape. As long as the impeller vanes are flexible and not stiff, you should be good to go.

 

[SkiDad]

No Title

Dear Pwnboat, Jiggs, Frank, Foodfisher:

just wanted to say thank you! As always you guys are a great help. I've been back on the water for a week now and been out 3 times. New LU runs great and wow what a difference getting up on Slalom. I'm up on slalom in 4 seconds now and there is not that lag to get up to speed it once had. Still running the 15p AL prop i had so i have to ski at 4500 instead of 4000. WOT rpm is 5700 now. My top speed is down 2 mph - but I can't complain. This will make a big difference when I get 2 or 3 more people in the boat with us.

I'm probably going to sell my spare 15p SST and pick up a 17p AL - that still might be plenty for my normal family runs.

I had quite a trip getting my old lower unit off - the water pump got stuck to the tube, it would not come out for anything. I had to remove the water pump screws while someone held the LU for me and then slide the LU out from the pump. then I had to hack saw the plastic piece several times to get it loose - not sure why b/c I bought the whole housing 2 years ago - must have been a defect. Donor engine had no such issues, LU was easy off and easy on to my engine.

I decided I'll change the impeller and paint it in the fall or spring. I did change the gear oil - it was pretty dirty.

 

[Jiggz]

Have you tried the 15p SS? A 15P SS has the equivalent of a 17P Al. So if you are planning on getting a 17p Al I suggest you give the 15p SS a try first.

 

[SkiDad]

Have you tried the 15p SS? A 15P SS has the equivalent of a 17P Al. So if you are planning on getting a 17p Al I suggest you give the 15p SS a try first.

i haven't tried the SST since the swap - i ran it a few times last year and it does get out of the hole a little faster but it ran 2 mph slower and seemed to keep my stern high and make the steering harder - maybe I'll try it again with the new lower but I'm betting it will be slower - i think it just the blade design with the hull design i have. I do have a 17p aluminum still but it needs re-hubbed - i remember my numbers last year with the original lower unit were

17p AL - 40 mph - 4600 rpm
15p AL - 38 mph - 5000 rpm
15p SS - 36 mph - 4700 rpm

 

[pnwboat]

I know my motor really likes that 2:1 ratio lower. Happy boating.

 

[Frank Acampora]

I have been a proponent of swapping in a 2-1 lower and going up 2 pitches for years. If you can find one, use a stock Chrysler stainless prop. Using a 17 pitch Chrysler stainless in place of a 15 pitch aluminum will give more engine RPM and higher top speed. It will really make that 125 sit up and move.

Stainless is more efficient than aluminum and typically the same pitch will turn faster by about 200 RPM (Given the same manufacturer and design). It takes a certain amount of horsepower simply to turn the prop. Stainless props generally have thinner blades than aluminum and thus will turn faster. Turning the higher pitch prop slower with the 2-1 ratio reduces parasitic prop drag allowing more horsepower to move the boat, instead of turning the prop.

Be aware that while I gained 8 MPH on my 140, eventually I did strip out the gears.