Why is my 1989 Evinrude V4 lower unit stuck and won't drop?
I am trying to drop the lower unit on my 1989 Evinrude VRO V4 to change the water pump impeller. I have taken out the four main bolts around the outside, but it is completely stuck and won't come off. What am I missing here?
Answer
Your lower unit is stuck because the shift rod linkage remains connected under the powerhead, or you missed the hidden bolt concealed beneath the trim tab anode. If you remove both and the gearcase refuses to drop, the driveshaft splines are seized in the crankshaft due to saltwater corrosion and missing marine grease.
The Hidden Trim Tab Bolt
Owners often remove the four visible retaining bolts on the midsection exterior and find the casing stuck. Evinrude V4 outboards from 1989 hide a fifth bolt. Locate the trim tab anode sitting just above the propeller. Remove the 1/2-inch bolt holding this zinc tab in place from above or below. Drop the anode out. Look straight up into the cavity. You will see a 9/16-inch bolt securing the rear of the lower unit to the exhaust housing. Remove this fastener. The unit should now break its seal.
Disconnecting the Shift Rod
If the casing drops a quarter of an inch and hangs rigidly, your shift rod remains attached. On a 1989 Evinrude V4, the disconnect sits right up under the powerhead rather than down by the water screens.
- Remove the main engine cowling and look below the bottom carburettor on the starboard side.
- Locate the shift linkage lever. You will see the top of the vertical shift rod ending in an eyelet.
- This connection is secured by a small hitch pin, a cotter pin, or a 3/8-inch hex-head retaining bolt depending on your specific V4 block.
- Remove this pin or bolt completely. Do not drop it into the lower belly pan. Retrieving it requires a magnetic pickup tool and hours of lost time.
- Push the linkage arm sideways out of the shift rod eye. The rod can now drop through the midsection.
Freeing Seized Driveshaft Splines
If you disconnected the shift rod and removed all five bolts but the lower unit remains stuck, the steel driveshaft splines have rusted into the crankshaft bottom. This fault plagues older OMC two-strokes run in saltwater without regular water pump servicing.
Never strike the anti-ventilation plate with a steel hammer. The cast aluminium will shatter instantly and cost you upwards of £500 for a replacement casing. Use a heavy dead-blow mallet instead. If you can open a hairline gap between the casings, drive hardwood wedges evenly into the seam on both the port and starboard sides. Do not use metal screwdrivers or chisels. They will permanently ruin the mating surfaces.