Need Honda guru: BF90A lower unit

[lund_prosport]

I have a 1997 BF90A LRTA BBBL 1003361 that needs a lower unit.

I can find a 2005 or 2006 lower unit. Will the newer lower unit work on the 1997? As far as I know the pre-EFI BF90s are the same with respect to the lower unit.

Thanks for any input.

 

[hondam]

They are NOT all the same, the early ones used a modified mercury lower unit and then Honda started making their own. I believe the 97 was still the Mercury lower unit. You can tell by the water pump housing, if its metal its a merc, if its composite then its a Honda. If you have the Honda lower unit then you can use the later model lower units although if you have the mercury lower unit its going to be harder to find what you need. You can NOT just bolt up a Mercury lower unit, Honda modified the lower unit to work with their engines, i dont know all the differences but i know at least the drive shaft needs to be changed.

 

[lund_prosport]

Link to a write up on this: http://www.michigan-sportsman.com/f...-with-1999-2006-honda-made-lower-unit.561441/

This description is specifically for Honda outboard 1997 BF90AT LRTA BBBL 1003361

It applies to 1997 and 1998 Honda BF75 and BF90 outboards with Mercury made lower units.

This is a 90hp motor with a 20? shaft, right hand rotation used in a single engine freshwater application.

Description of replacement of a 1997 Mercury-made lower unit with a 2006 Honda-made lower unit.

Parts required (quantity = 1 for all):
41100-ZW1-B10ZA CASE, GEAR *NH282MU* : 1999-2006 Honda-made lower unit
24320-ZW1-B00 ROD A, SHIFT : shift rod between lower unit and power head
90506-ZW1-B00 WASHER : propeller thrust washer
90508-ZW1-B00 WASHER (18.5MM) : plain washer
90301-ZW1-B00 NUT, CASTLE (18MM) : propeller nut
90758-ZW1-B00 PIN, SPLIT (4.0) : propeller cotter pin

Parts are available at:
Atlantic Marine Service
337 Redoubt Rd.
Yorktown, Va. 23692
attn: Mr. Scott Oberndorfer
Phone: (757) 833-6666/4
Fax: (757) 833-6662
scott@atlanticmarineva.com
parts@atlanticmarineva.com

Parts discarded (none are compatible with the 1999-2006 lower unit):
Mercury-made lower unit
Shift rod
Water pump coupling
Propeller thrust washer
Propeller nut
Propeller star washer

Notes on parts:
- new Honda-made lower unit
- - comes with main driveshaft, water pump assembly including impeller, and anodes.
- - has plastic water intake screens
- - has oil fill, drain and ?wash? screw plugs on port side
- - has streamlined aft section above propeller
- - has larger surface area and more streamlined steering trim fin
- - uses a cotter pin to secure the propeller nut
- old Mercury-made lower unit
- - has integrally cast water intake holes
- - has oil drain and fill screw plugs on starboard side
- - uses a star washer to secure the propeller nut

Tools for disassembly:
14mm 3/8? drive socket with short extension
14mm box end wrench
27mm 1/2? drive socket
Locking pliers
Hammer (claw, small sledge or ball peen)
Rubber mallet
Screwdriver
Needle nose pliers

Tools for assembly:
14mm 3/8? drive socket with short extension
14mm box end wrench
28mm 1/2? drive socket
Torque wrench
Needle nose pliers

Documents:
- Honda parts catalogs on boats.net
- Honda service manual. Email me for a copy: wkroppe@yahoo.com

Steps for disassembly:
- Move shift control to neutral
- Tilt motor to highest position
- Use screwdriver to flatten propeller star washer
- With 28mm socket remove propeller nut
- Remove star washer propeller and thrust washer
- With 14mm box end and socket wrenches loosen 4 short screws and 1 long screw holding lower using to extension housing by 1/4?
- Use rubber mallet to loosen lower unit
- Continue gradually loosening 5 screws, using rubber mallet to assist, until the lower unit is free, but held in place with screws.
- Support the weight of the lower unit, and remove all 5 screws.
- Withdraw the lower unit. Check to see that the water pump coupling came out with the lower unit. Remove the water pump coupling from inside the extension housing using needle nose pliers.
- Using locking pliers and a rag or paper towel, clamp the bottom of the shift rod.
- Using a ball peen or similar hammer, sharply strike the locking pliers to free the shift rod. The shift rod is secured by an internal snap ring and will come out with some force.
- Remove the shift rod.
- Visually check for unanticipated damage.
- NOTE: Do not remove the e-clip where the shift rod enters the powerhead. I did this and it caused me 2 hours of work that was not needed.
- Time required for disassembly: approximately 30 minutes.


Steps for assembly:
- Remove engine cowling/cover.
- Remove plastic flywheel cover.
- Confirm the shift lever at the helm is in the neutral position.
- Orient the flat part of the new shift rod in the forward direction.
- Insert the shift rod until it clicks in the snap ring in the powerhead. Visually check the bottom of the shift rod socket so see that the flat part is facing in the forward direction.
- Visually check the lower unit to ensure the flat part of the shift shaft is facing in the forward direction.
- Slowly insert the lower unit. If the main driveshaft does not cleanly engage the spline in the powerhead, support the lower unit with one hand at the steering trim fin, and with the other hand turn the flywheel by hand. Continue this until the driveshaft spline fits smoothly into the powerhead spline.
- Loose fit all 5 screws.
- Gradually tighten all 5 screws in a star pattern, ensuring that the lower unit smoothly engages against the extension housing.
- Tilt the engine down to the lowest position possible.
- Test the shift movement by moving the shift control at the helm into forward gear, and then neutral gear. Full throttle movement should be available in both directions. If proper shift function is not possible, the shift shaft is not properly engaged. Remove the lower unit and repeat the assembly process, noting the position of the shift rod in the extension housing, and the shift rod in the lower unit.
- After successful shift function confirmation, tilt engine to highest position.
- Install propeller thrust washer with the large end of the tapered hole facing forward.
- Torque 5 screws in a star pattern to 25 ft-lbs.
- Install the propeller.
- Install the propeller plain washer.
- Install the propeller castle nut and torque 1 ft-lb. Fit the cotter pin. If this is not possible, tighten the propeller nut until the cotter pin fits. Max torque of the castle nut is 45 ft-lbs.
- Install the flywheel cover and engine cowling.
- Install water supply (e.g with ?muffs?)
- Turn on water supply
- Prime engine with squeeze bulb.
- Start engine, and check proper gear and propeller function by running the engine for one minute in each direction forward and reverse.
- Time required for assembly and testing: approximately 2 hours at a careful pace.

 

[tommarvin]

What's wrong with the lower unit that was on the motor?