Maintaining Johnson/Evinrude 9.9 & 15 hp outboards 1974 – 2006   (Converting Shaft lengths)
1974		1996

Lower Units Not Changed That Much in 30 Years :  The same basic lower unit is still used on the latest motors for both the 2 stroke & 4 stroke motors.   The gears & water pump are the same.  After 1993 the exterior was changed slightly to incorporate a built in place for zinc anodes & the water intake screen  was changed from an internal screen to 2 external screw on screens.  Other than that the older ones & the newer ones appear the same.

Converting motors with one shaft length to another length :  This question comes up enough that it needs it's own article.   First some background as to the whats & whys involved.

Shaft Length Differences :  The standard motor comes to mount on a regular boat's 15" transom.  This is designed so that the bottom of the boat is even with the cavitation plate of the motor.  The cavitation plate is the flat fin in the lower unit housing above the prop.  The difference in the longshaft unit is that it has a 5” aluminum extension the same physical size as the exhaust housing, to fit a 20" transom.  This unit is supplied as a kit, comprising the extension, a new 5” longer driveshaft, a 5” longer shifting linkage rod, a copper water tube long enough to couple between the water pump & the old tube from the power head & 6 more bolts to assemble it to the gear case.  

The SailMaster is basically the same 9.9 motor with electric start & a 10" shaft extension for use on sailboats.  

When replacing the water pump impeller if your motor has the longshaft, you first remove the upper bolts attaching the spacer from the exhaust housing.  Once you have the gear case unit & the spacer off the exhaust housing, then you will have to remove the extension unit to get to the water pump that is still in it’s original location on the top of the lower gear case unit.

1978 Regular, or 15" Short shaft	1986,  20" Long shaft	1992 Sailmaster, 25" Extra Long shaft

As you can see in the above illustrations, The different length motors either have no or 2 different height spacers installed between the lower unit & the upper exhaust housing.   A conversion also requires the proper driveshafts & other related parts.

Actual Removal of Gearcase or Lower Unit to Access the Driveshaft &Water Pump :  If the motor has been used in saltwater to any degree, I will guarantee that at least a few of the bolts will be seized in & will be twisted off.  I will cover this in a separate section.   Have the motor mounted either on the transom of the boat, or on a motor stand or saw horses.  It also will make a slight difference in the procedure whether the motor is a long shaft or not. There are 6 stainless, 1/4” bolts with 3/8” heads that come in from the bottom & are bolted up into the exhaust housing assembly.  If it is a short shaft, they are the only ones there.  If however it happens to be a longshaft, there is a 5” extension, or if a Sailmaster a 10" extension between the lower unit & this housing.  If so, then remove the upper 6 bolts.  The lower 6 bolts attach this extension to the lower unit. 

When you get these 6 bolts removed, the gear case unit should drop down about 1/2”.  If it does not you may have to tap it with a plastic mallet.  Shift the gearshift into forward which will allow the shifting linkage shaft to drop down & align the retainer bolt with the gap between the housings.  When the lower unit does slide down, there will be, inside the housing in the front right hand side, a connector that is a strap with 2, ¼” holes top & bottom & 2 bolts that are screwed in sideways.  These bolts go in a circular groove of the shifting rod, & hold it in place.  Remove only the top screw.  It has a hex head & also a screwdriver slot.  Once this screw is removed the gear case unit can be moved downward & off.

There is a stainless steel exhaust baffle screen that is slid into the rear particians lower exhaust housing at the juncture where the gear case unit fits together on all motors except the first year or two.  This baffle has many small holes in it & apparently helps reduce some of the exhaust noise.

The driveshaft may have a O-Ring around it on the splines that engage the motor crankshaft.  The earlier motors had a groove around the shaft for this O-Ring, while the newer ones had the O-Ring in a internal groove in the lower end of the crankshaft.  If it on the shaft, remove it until you are ready to re-install the parts.

Now on the gear case unit, you will find 4 bolts holding the water pump with the driveshaft going thru this pump housing. The water pump housing can be of pot metal or plastic, depending on the vintage.  The plastic/nylon type is the newer style.  If it is the pot metal type & has been using saltwater, you may consider replacing the whole pump with the plastic style instead of just the impeller, as the internal portion where the impeller rubs will be corroded & will soon chew up a new impeller.

Unscrew these 4 bolts & slide the water pump housing up & off the driveshaft.  The front 2 screws are longer than the rear ones.  Keep this in mind when you reassemble the unit.  Make note of which direction the impeller vanes are facing, as you need to install the new impeller the same way, otherwise it will not pump right.  Now also there will be a key that holds the impeller to the shaft.  Save this also for reassembly.

If you take it apart & the impeller appears still intact, you should consider inspecting it further, as it is not uncommon for the inner hub to become unbonded from the rubber impeller, allowing the hub to spin inside the impeller rubber or a vane may become hardened & break off.   Also some aftermarket impellers can be thinner than the originals, not sealing on the sides, sucking air & creating erratic pumping.

Shown below are the differences in the short shaft & long shaft shifting rods & drive-shafts, plus the 5" extension assembly required .  Also needed is the 5" water tube extension not shown.

Short Shaft converted to Long Shaft :  Motors can be converted from short to long, or long back to short with the proper parts.  When converting a short shaft to a long shaft, you will have to purchase a conversion kit, which includes a 5" housing spacer with the 6 bolts, a new 5" longer driveshaft, longer shifting rod, & a water pump tube extension.    This can be purchased off e-Bay many times, but possibly without all the needed parts.

To do this conversion, you need to remove the lower unit just as if you were replacing the water pump impeller.  You will need the proper extension assembly (usually the 5" white adapter shown above) which has a rubber spacer inside for the alignment of the water tube, & a plastic round hollow spacer that the driveshaft does thru.   Also an appropriate longer driveshaft & shifting rod.   You also need the another 6 mounting bolts & a water tube extension.   

You should be able to buy these kits from any Johnson/Evinrude dealer, but the price may reach $300 as a guess.   However if you go to some marine dealers they may have a used unit or enough parts to make up one.   Or go to one of the used OB parts dealers online, they should have them for 1/2 of that.   Or go to http://www.ebay.com/ & type in "johnson 9.9", they show up occasionally & can go for $50 - $100.   However these guys may not sell the complete "KIT" and only the extension or the long shaft.   The reason is many times the person selling the parts does not really know what it takes to do the job.  Don't pay a high price for only part of the set.  If you only get the normal parts of it (extension & driveshaft), you then need the longer shifting rod, the rubber water pump alignment spacer, the white plastic tube spacer & a water tube extension, however these should be available from the dealers, at a cost of course.  The water pump alignment spacer sells for $12 & the longshaft shifter rod sells for about $13.  So try to pick a unit that has as many parts as needed.

Long Shaft converted to Short Shaft :   This would most likely not be encountered as often as there are way more standard length shafts motors out there than long shafts, with the long shafts typically used as secondary motors on larger boats that need the extended length, while the bulk of these motors sold during the time frame they were made were used on standard or smaller boats.  

I have shortened long driveshafts & welded them back together.  Short shaft overall length is 22 3/8".   If in doing this you would finally have to be sure that it is straightened so there would be no wobble.  Again if doing this, go to a welding shop that can weld stainless with a wire feed welder (more penetration), grind the mating ends to a cone type taper with the center about 3/16" dia left.   Place them in an angle iron that is mounted in a vise so it forms a Vee to hold it in line for the initial weld. Once welded & initially straightened, the weld can be rough turned down to slightly oversize to the outside dia. & at this time while in the lathe, ran, straightened & ran again until it is close with the least amount of wobble.

Or another method would be to make a sleeve, 2 to 3" long that can be slid over the shaft & have it welded to the shaft on each end of this sleeve. This would change your installation procedure slightly as the water pump unit then would have to be slid onto the shaft from below before you installed it into the lower unit. The splice would need to be maybe mid point between the water pump & the upper end, or at least enough above the water pump so the pump body could be installed above it's final location & then slid down to mount up. 

The shifter rod can just be cut off & the bend put back in the top end.  You will not have to re-groove it like the original, as you just need to grind a notch in the location that the bolt goes thru that attaches to the upper rod. Be sure however that the notch is in the exact same relationship from the top, but the 5" lower, as this times the shifting.   You can adjust this slightly by how many threads you screw it into the lower unit shift linkage.

In converting a factory long shaft to a short shaft, you can simply cut off the 3/8" copper water tube.  Cut off  5", or so that the tube stops 1/2" above the exhaust housing bottom.  The best way to do this would be to mark it & use a Dremel Tool with a part off stone.   Be sure to remove any rough edges, as this has to fit into the rubber grommet in the top of the water  pump housing, & you can't really see if it is going or not, as it is mostly out of sight at the time.

One of you internet readers on the east coast inquired about doing this above conversion.  I suggested he contact a marine repair shop & see if they had a used driveshaft instead of cutting & welding his.  The mechanic said it was impossible to do this conversion.  I wonder if he was drinking more than just water.