Yamaha 2.5hp Outboard Service
Mariner Water Pump Refurbishment
The water pump of the Mariner 2HP is housed in the lower, gearbox, casting of
the outboard. Obtain the Yamaha water pump service kit Part number 6A1-W0078-01.
Also ask for a second seal, for the lower water pump (It is exactly the same as
the one in the kit). The job takes about three hours when all the tools are to
To gain access to the pump impeller and pump body follow the steps:
- Remove the propeller taking care not to loose the drive pin.
- Locate the lower casting and remove the two 10mm bolts, one located on the
upper side front and the other on the lower side, just above the propeller
- Gently but firmly ease the gearbox complete with water pump and any
internal pipes from the outboard leg. This usually requires two levers
applied on opposite sides. The pressure should be applied evenly and the gap
must be kept parallel to avoid damage to the casting
- Remove the two bolts securing the gearbox faceplate and gently but firmly
remove the faceplate. If the propeller shaft is kept pointing up during this
operation then the oil will be retained in the gear casing.
- Once the faceplate is removed, drain the oil and then carefully remove the
circlip from the end of the drive pinion.
- Once the lower housing is removed the two 8mm bolts securing the water
pump upper housing may be removed and the water pump impeller is accessible.
Now carefully withdraw the drive shaft noting the position of the pinion and
thrust washers positioned on the drive shaft immediately behind the pinion.
Also be careful not to loose the impeller drive pin located in the drive
shaft just below the water pump upper housing. Remove the impeller.
- Disassemble the drive shaft tube from the pump upper body together with
the drive shaft. This may prove to be quite a difficult task as the tube is
quite thin walled and can be corroded into the pump housing. Be patiently
||8. The stainless steel pump liner
can be removed using a gaz torch to carefully heat the area whilst prising
out the body and plastic seating. Remove the rubber seal.
||9. Clean the seal housing and
replace the seal. Apply grease to the seal and a liberal coating of yellow
chromate 'Duralac' to the cleaned pump casting.
||10. Align and assemble the SS pump
lining into the plastic liner and, taking care to align everything
correctly, position these components into the casting. Clear surplus
material from all outlets.
||11. Carefully clean
the casting and replace the seal, 'O'Ring and outlet grommet. Careful not to
loose the two locator lugs. NOTE: The seal is not part of the service kit so
make sure you obtain one at the time you purchase the pump service kit.
Ensure the faceplate is clean. Carefully offer up the drive shaft through
||12. Fit the drive
shaft cover tube, using a little MS4 silicone grease. Coat the faceplate of
the housing with yellow chromate and place the S.S. pump top plate in
position. Locate the impeller drive pin and refit the impeller. Now to
assemble the pump and gears.
13. Locate the drive shaft into the lower housing and slowly bring the two
halves together until the thrust washers and pinion drive can be assembled onto
the end of the drive shaft. Refit the circlip. Refit the gearbox faceplate,
renewing the 'O' Ring as required, and refill the gear oil.
14. Carefully bring together the two parts of the outboard (I coated the
mating surfaces with yellow chromate prior to assembly) ensuring that the drive
tube and water cooling pipe locate correctly in the appropriate grommets.
Tighten the two 10mm bolts evenly. I ran the engine at this stage, without the
prop, in a large bucket. Once tested, the propeller can be mounted and the
engine put back into service.
Do not run the engine dry as this will quickly damage the impeller and cause
unnecessary pump wear.
This page was last updated on
Tuesday, September 18, 2018 11:05
by Richard Spencer.