CONTINUOUSWAVE

A few weeks ago I hit something and bent my propeller, a four-bladed stainless steel Trophy Plus 17-pitch. It wasn't damaged too badly, and I used it for a few outings with no problems.

Last week I replaced it with my backup propeller, a 3-bladed aluminum Black Max 13-pitch. Since installing that propeller, I've found that I often cannot shift from neutral to reverse when the engine is not running. This is sometimes necessary to center the temperamental neutral safety switch. When the engine is running, it shifts fine.

Today I replaced the Black Max with a new four-bladed stainless Spitfire X7 15-pitch. I also replaced the old Flo-Torq III hub with a new Flo-Torq SSR hub. With the engine running, shifting is smooth with much less of a CLUNK than I had with the Trophy Plus. More on the Spitfire X7 after I collect some data. But the problem of not shifting into reverse when the engine is running remains.

The engine is a 2003 Mercury 115 FOURSTROKE with a 2.03:1 gearcase.

Because everything works well when running, I don't think it's a shifter or shift cable adjustment problem.

Any ideas what it might be?

-Bob

I got nothin'.

THAT'S unusual... :-)

The typical outboard engine shift mechanism is rather crude, and I don't think that having a problem shifting when the engine is not turning over is all that unusual. You might try rotating the propeller by hand and see if that helps the shifting.

About the only adjustment would be on the shift linkage to the remote controls. A Mercury factory rigging manual or engine service manual might have a procedure to setting up the shift linkage.

The change to a lighter weight propeller (the aluminum three-blade) from a heavier propeller (the steel four-blade) does not make me think of any correlation with the difficulty in shifting.

As I recall--this may not be correct--in the typical gear case the pinion gear on the engine drive shaft is ALWAYS engaged with both the forward gear and the reverse gear. The "shift" is really movement of a crude clutch mechanism on the propeller shaft that either engages the forward gear to the propeller shaft (for FWD), or neither gear (for NEUTRAL), or the reverse gear (for REV). What is moving is a sliding mechanism on the propeller shaft that locks one of the gears to the shaft or none of the gears.

Jim, your summary matches my understanding, though I've never had one apart. I could believe that shifting with no rotation of the driveshaft could be difficult, except that it didn't do that before and now it does. In my experience "coincidence" is often cause-and-effect that hasn't been discovered yet. I'll grease and adjust the throttle and shift cables, they are due for that anyway, and see if that improves things.

A damaged propeller, even though seemingly usable, will cause a lot of unwanted engine vibration. This can lead to metal fatigue, loosened fasteners and loosened electrical connectors. Carrying a spare is rather redundant if it is not used as soon as possible when needed.

I'm sure you've done a careful visual inspection for damage. I would next inspect for loose fasteners, concentrating on those that could cause some misalignment or anything related to shifting. I doubt that there is any relation between your shifter and electrical system, however, I recall that some engines have a momentary ignition interruption when shifting. That may be worth a look. It would seem to be unnecessary as shifting into forward is not a problem but I don't know how the process works.

There are a surprising number of videos about Mercury outboard engine troubleshooting and repair on "Youtube".