1972 Mercury 500 - Stuck in Reverse Gear, Water Pump Question

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Author Topic:   1972 Mercury 500 - Stuck in Reverse Gear, Water Pump Question

Buckda posted 07-05-2011 07:14 PM ET (US)
I have a 1972 Mercury 500 four cylinder 50 HP motor. The motor runs very smooth and is a great overall performer, however, I have two problems that I'd like a little help with.
Background - I just changed the water pump/impeller for the first time by myself, referencing this site and other internet sources for information on the job.
1). Upon re-installing the lower unit, I discovered that it was stuck in forward gear. Referencing some online resources, I determined that the lower unit gear shaft needed to be turned counter clockwise (CCW) to find the "neutral" position before re-inserting the lower unit. I did this *or thought I did*.
2) Upon starting the engine (this time in neutral), I ran the motor on muffs in the driveway for about 45 minutes. The heads were warm to the touch, but by no means hot. It was about 95 degrees outside in the sun and the heads were about 10-15 degrees warmer than ambient. The confidence stream/indicator never produced a stream of water from the lower portion of the cowling.
3) Upon test driving the boat on a local lake last night (air temperature 75 degrees and moist after thunderstorms, water temperature 83 degrees), the boat ran like a champ for about an hour and a half. The whole time with no confidence stream coming from the motor....and the whole time with a cool poerhead and plenty of performance at all speeds, and shifting into and out of gear several times.
4) upon returning to the ramp, we heard a higher pitched metallic clink when shifting into neutral. Then I shifted into reverse to further reduce forward momentum into the dock. When I did this, the clink returned and the engine remained in reverse even as I shifted the control box into the neutral and even forward positions.
5). The control box/cables appear to be working properly.
The questions follow:
A) should I be concerned that there is no water stream from the motor cowling, even though the water pump appears to be working?
B) Is it possible that I shifted the lower unit gear shaft past neutral and "almost" into reverse when adjusting it, leading to the problem of it being "stuck" in reverse?
Any thoughts?
One other thing - all but 1/3 of a single vane was left on the old impeller when I changed it....should I be concerned where that debris went, or do you think it simply went out through the waste water dump via the propeller hub?

Tohsgib posted 07-05-2011 07:55 PM ET (US)
Your vane is probably what is clogging something. Mercury fortunately does not use the indicator as part of the whole process so yes it can run fine with no indicator but that should be fairly easy to clear as it is basically just a hose. I would drop the lower again and find out if your problem is in the foot itself or shift rod, etc. Sounds like you might have puked it but a good used unit should be EASY to find and cheap as they sold billions of those engines over 30+ years.
Binkster posted 07-05-2011 10:16 PM ET (US)
On a unrelated note, would this motor happen to be a short shaft and electric start? If so I might be interested in buying it if you ever want to sell it.
Buckda posted 07-07-2011 09:15 AM ET (US)
The problrm appears to be solved.
The confidence stream was blocked by some mud and was cleared using a tip from this forum; using some line from a weed wacker.
I dropped the lower unit and re-adjusted the lower shift shaft to ensure it was in neutral and reinstalled the unit.
Ran the boat for 2 hours last night with strong confidence stream and no problems with shifting.
Rich: the engine runs like it was new. No intentions to sell anytime soon. It is the single best Merc I've ever had the chance to own/run. Carl K would be proud that as an antique, it is still proviving hours of enjoyment on the water.

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Author	Topic: 1972 Mercury 500 - Stuck in Reverse Gear, Water Pump Question
Buckda	posted 07-05-2011 07:14 PM ET (US) I have a 1972 Mercury 500 four cylinder 50 HP motor. The motor runs very smooth and is a great overall performer, however, I have two problems that I'd like a little help with. Background - I just changed the water pump/impeller for the first time by myself, referencing this site and other internet sources for information on the job. 1). Upon re-installing the lower unit, I discovered that it was stuck in forward gear. Referencing some online resources, I determined that the lower unit gear shaft needed to be turned counter clockwise (CCW) to find the "neutral" position before re-inserting the lower unit. I did this or thought I did. 2) Upon starting the engine (this time in neutral), I ran the motor on muffs in the driveway for about 45 minutes. The heads were warm to the touch, but by no means hot. It was about 95 degrees outside in the sun and the heads were about 10-15 degrees warmer than ambient. The confidence stream/indicator never produced a stream of water from the lower portion of the cowling. 3) Upon test driving the boat on a local lake last night (air temperature 75 degrees and moist after thunderstorms, water temperature 83 degrees), the boat ran like a champ for about an hour and a half. The whole time with no confidence stream coming from the motor....and the whole time with a cool poerhead and plenty of performance at all speeds, and shifting into and out of gear several times. 4) upon returning to the ramp, we heard a higher pitched metallic clink when shifting into neutral. Then I shifted into reverse to further reduce forward momentum into the dock. When I did this, the clink returned and the engine remained in reverse even as I shifted the control box into the neutral and even forward positions. 5). The control box/cables appear to be working properly. The questions follow: A) should I be concerned that there is no water stream from the motor cowling, even though the water pump appears to be working? B) Is it possible that I shifted the lower unit gear shaft past neutral and "almost" into reverse when adjusting it, leading to the problem of it being "stuck" in reverse? Any thoughts? One other thing - all but 1/3 of a single vane was left on the old impeller when I changed it....should I be concerned where that debris went, or do you think it simply went out through the waste water dump via the propeller hub?
Tohsgib	posted 07-05-2011 07:55 PM ET (US) Your vane is probably what is clogging something. Mercury fortunately does not use the indicator as part of the whole process so yes it can run fine with no indicator but that should be fairly easy to clear as it is basically just a hose. I would drop the lower again and find out if your problem is in the foot itself or shift rod, etc. Sounds like you might have puked it but a good used unit should be EASY to find and cheap as they sold billions of those engines over 30+ years.
Binkster	posted 07-05-2011 10:16 PM ET (US) On a unrelated note, would this motor happen to be a short shaft and electric start? If so I might be interested in buying it if you ever want to sell it.
Buckda	posted 07-07-2011 09:15 AM ET (US) The problrm appears to be solved. The confidence stream was blocked by some mud and was cleared using a tip from this forum; using some line from a weed wacker. I dropped the lower unit and re-adjusted the lower shift shaft to ensure it was in neutral and reinstalled the unit. Ran the boat for 2 hours last night with strong confidence stream and no problems with shifting. Rich: the engine runs like it was new. No intentions to sell anytime soon. It is the single best Merc I've ever had the chance to own/run. Carl K would be proud that as an antique, it is still proviving hours of enjoyment on the water.